W2MMD VHF / UHF / Satellite Tracking Station
Building The GreenCube Satellite Station
By Jon Pearce, WB2MNF
The Skunkworks team at the Gloucester County Amateur Radio Club is always looking for new projects to dig into, learn from, and build something new. So when we found that the “GreenCube” satellite had been launched and was a very different type of device we started figuring out how we could work it.
The GreenCube satellite is described in this link , so we won't spend a lot of time covering it here. It has two primary differences from other ham satellites - first, it's in a medium earth orbit (MEO) about 3728 miles above the earth (by contrast, the International Space Station is about 250 miles above the earth). This means several things - its coverage footprint is far larger than any other current amateur satellites and its operating window over a particular point on earth will be measured in hours, not minutes.
The second significant difference is that it utilizes a “digipeater”, which is a digital repeater that receives digital signals from earth stations and retransmits them from the satellite. Given that the footprint of the satellite will cover an almost an entire hemisphere of the earth there may be thousands of operators trying to access it simultaneously; therefore only a communications protocol that involved short transmissions would be practical. GreenCube digital transmissions last about 1/4 of a second, so many stations can be transmitting over a short period of time and still be heard by the satellite.
Most other amateur radio satellites are “full duplex”, meaning that they transmit and receive on different frequency bands, and that users can hear themselves in the downlink of the satellite. This is important because of the “Doppler shift” present in satellite operations in which frequencies need to be adjusted to compensate for the speed of the satellite as it moves overhead. GreenCube differs in that it is “half duplex”, meaning the transmission and reception occur on the same frequency (435.310 MHz ). This meant several adjustments to the station configuration.
GCARC Satellite Station
The satellite station at the W2MMD Clubhouse is close to being state-of-the-art. For receiving it uses an SDR Play software defined radio coupled with the SDR Console user interface that allows the operator to visualize the entire passband of the satellite and make adjustments where necessary. A Yaesu 847 transceiver is used as a transmitter. The satellite antennas are among the best available from M2 - the 70 cm antenna is a 42 element 436CP42UG crossed Yagi and the 2 meter antenna is a 22 element 2MCP22 crossed Yagi. Antenna rotation is handled by a venerable Yaesu GS-232 rotator with an AMSAT LNB controller. Satellite mode switching for the antennas is usually handled by an Arduino-controlled relay switch, but because of the renovations at our satellite room it was temporarily replaced by two manual coaxial switches that switch the two antennas between the transmitter and the receiver.
This configuration works well for full duplex satellites but had to be modified for GreenCube’s half duplex operation. Initially we manually switched the 70 cm antenna between transmit and receive but later were able to add a MFJ 1708B RF-sensing antenna switch that would disconnect and ground the SDR radio when the transmitter was transmitting. That let both the 847 and the SDR Play connect to the 70 cm antenna.
Two other functions are necessary for satellite operations - the antennas must be rotated to continually point at the satellite as it moves through the sky, and the transmit and receive frequencies must be adjusted for the Doppler shift that occurs when working satellites that are moving thousands of miles an hour. Those functions are both handled by the PST Rotator program, which we've found to work extremely well with all satellites.
The GreenCube Software
When we initially started looking at the GreenCube satellite the online references seemed to point us to a receiver that needed to be constructed from GNU radio, which was beyond our capabilities. This initially dissuaded us from pursuing that satellite until we located the satblog.info site that contained the digipeater and telemetry software. We also tried different variations of the UZ7HO “Soundmodem” software trying to identify the proper version for GreenCube until we noticed a download link on their website for “greentnc.zip” that contains the modem software written specifically for the satellite. Soundmodem audio is fed from SDR console through a virtual audio cable and it decodes the audio packets into raw data. That data is fed through a TCP port into the GreenCube decoder software that lets the operator view incoming packets, call CQ or respond, and also log the QSO. It’s a really neat set of software.
The final program is the telemetry receiver, which updates about every 45 seconds from packets transmitted by the satellite. This displays current values for various telemetry fields from the satellite, with the new vertical bar appearing in the lower panel with each new set of telemetry. There's an accompanying program that will upload this data to the SatNOGS database but unfortunately I was not able to overcome a Windows error that occurs when I ran this program.
Initial issues
Initially we were somewhat successful with this configuration, working a number of stations throughout the middle of a pass. Two problems became quickly apparent - although we had a 42 element Yagi antenna we weren't able to decode signals near the beginning and end of the pass. Unfortunately, this is where the more interesting stations appear since they're also the more distant stations. Most other GreenCube stations appeared to have less sophisticated antennas but are also using preamplifiers mounted at the antenna, which we decided we needed.
The other issue was that that the transmitted signal frequently didn't seem to be heard by the satellite. The FT-847 is only rated at 20 watts output on 70 centimeters and ours seemed to be putting out significantly less power, which doesn't appear to be enough to create a reliable and readable signal at the satellite. From some online research we found that some other stations appeared to be using Icom IC-9700 transceivers that run 70 watts on 70 centimeters, so we decided we needed to upgrade to a more powerful radio.
A confounding problem also appeared to be finding the correct base frequency for transmitting. Setting PST Rotator to the published frequencies required adjustment to make the received audio frequency center around 1500 Hz. But what about the transmit frequency? We didn't know exactly where the satellite would be listening, and being off by several hundred Hertz could make us unreadable. Finally, we found a reference telling us to set both frequencies lower by about 800 Hz, which put the received frequency perfectly in line for decoding by Soundmodem and also appeared to create the correct transmit frequency to be decoded by the satellite.
Adding the preamp
Al KB2AYU came to our rescue on the receive issue with a mast-mounted preamplifier for 70 centimeters that he installed on the antenna boom. We installed the power injector at the feedline switch and found that the preamp significantly improved receive performance. That preamp was initially switched out of the line by sensing the RF; however we later were able to hard-switch it using a direct connection to the PTT output of the transceiver.
Replacing the 847 with the 991A
The issue of low power output was solved by replacing the FT-847 transceiver with a newer FT-991a radio from my personal station. Initially we had some COM port issues which we traced down to having defined a virtual COM port at the same location that Windows assigned to the standard COM port of the 991. We also found that the 991 appeared to significantly reduce the high frequency component of the audio signal when set in USB-DATA mode (we found this by using the calibration function in Soundmodem and looking at the output from the low and high tones, finding the high tone output being significantly reduced). We solved this by operating the radio in USB mode, not USB-DATA mode. The complication with this arrangement is that there is apparently no adjustment on the transceiver for the audio level coming in through the USB port, so we had to adjust this in Windows for the maximum level that would not kick in the ALC. Finally we decided that we had everything working as well as we could.
How does it work?
At this point the GreenCube station seems to work as well as we could possibly expect. We can decode signals virtually throughout the entire pass and can view our transmitted signals on the downlink most of the time. At this point we've worked 38 different countries on five continents, with the longest distance QSO being 11,000 kilometers between us and the station in Japan. We're hopeful to work satellite DXCC although we're not confident that there are actually 100 operational GreenCube stations within the potential footprint of the satellite from our location.
But so far working this satellite has been an exciting new challenge, allowing us to learn much about how our equipment operates and how to create success on a digital half duplex satellite. We are planning to continue active operation on this satellite, so if you see W2MMD please give us a shout.
By Jon Pearce, WB2MNF
The Skunkworks team at the Gloucester County Amateur Radio Club is always looking for new projects to dig into, learn from, and build something new. So when we found that the “GreenCube” satellite had been launched and was a very different type of device we started figuring out how we could work it.
The GreenCube satellite is described in this link , so we won't spend a lot of time covering it here. It has two primary differences from other ham satellites - first, it's in a medium earth orbit (MEO) about 3728 miles above the earth (by contrast, the International Space Station is about 250 miles above the earth). This means several things - its coverage footprint is far larger than any other current amateur satellites and its operating window over a particular point on earth will be measured in hours, not minutes.
The second significant difference is that it utilizes a “digipeater”, which is a digital repeater that receives digital signals from earth stations and retransmits them from the satellite. Given that the footprint of the satellite will cover an almost an entire hemisphere of the earth there may be thousands of operators trying to access it simultaneously; therefore only a communications protocol that involved short transmissions would be practical. GreenCube digital transmissions last about 1/4 of a second, so many stations can be transmitting over a short period of time and still be heard by the satellite.
Most other amateur radio satellites are “full duplex”, meaning that they transmit and receive on different frequency bands, and that users can hear themselves in the downlink of the satellite. This is important because of the “Doppler shift” present in satellite operations in which frequencies need to be adjusted to compensate for the speed of the satellite as it moves overhead. GreenCube differs in that it is “half duplex”, meaning the transmission and reception occur on the same frequency (435.310 MHz ). This meant several adjustments to the station configuration.
GCARC Satellite Station
The satellite station at the W2MMD Clubhouse is close to being state-of-the-art. For receiving it uses an SDR Play software defined radio coupled with the SDR Console user interface that allows the operator to visualize the entire passband of the satellite and make adjustments where necessary. A Yaesu 847 transceiver is used as a transmitter. The satellite antennas are among the best available from M2 - the 70 cm antenna is a 42 element 436CP42UG crossed Yagi and the 2 meter antenna is a 22 element 2MCP22 crossed Yagi. Antenna rotation is handled by a venerable Yaesu GS-232 rotator with an AMSAT LNB controller. Satellite mode switching for the antennas is usually handled by an Arduino-controlled relay switch, but because of the renovations at our satellite room it was temporarily replaced by two manual coaxial switches that switch the two antennas between the transmitter and the receiver.
This configuration works well for full duplex satellites but had to be modified for GreenCube’s half duplex operation. Initially we manually switched the 70 cm antenna between transmit and receive but later were able to add a MFJ 1708B RF-sensing antenna switch that would disconnect and ground the SDR radio when the transmitter was transmitting. That let both the 847 and the SDR Play connect to the 70 cm antenna.
Two other functions are necessary for satellite operations - the antennas must be rotated to continually point at the satellite as it moves through the sky, and the transmit and receive frequencies must be adjusted for the Doppler shift that occurs when working satellites that are moving thousands of miles an hour. Those functions are both handled by the PST Rotator program, which we've found to work extremely well with all satellites.
The GreenCube Software
When we initially started looking at the GreenCube satellite the online references seemed to point us to a receiver that needed to be constructed from GNU radio, which was beyond our capabilities. This initially dissuaded us from pursuing that satellite until we located the satblog.info site that contained the digipeater and telemetry software. We also tried different variations of the UZ7HO “Soundmodem” software trying to identify the proper version for GreenCube until we noticed a download link on their website for “greentnc.zip” that contains the modem software written specifically for the satellite. Soundmodem audio is fed from SDR console through a virtual audio cable and it decodes the audio packets into raw data. That data is fed through a TCP port into the GreenCube decoder software that lets the operator view incoming packets, call CQ or respond, and also log the QSO. It’s a really neat set of software.
The final program is the telemetry receiver, which updates about every 45 seconds from packets transmitted by the satellite. This displays current values for various telemetry fields from the satellite, with the new vertical bar appearing in the lower panel with each new set of telemetry. There's an accompanying program that will upload this data to the SatNOGS database but unfortunately I was not able to overcome a Windows error that occurs when I ran this program.
Initial issues
Initially we were somewhat successful with this configuration, working a number of stations throughout the middle of a pass. Two problems became quickly apparent - although we had a 42 element Yagi antenna we weren't able to decode signals near the beginning and end of the pass. Unfortunately, this is where the more interesting stations appear since they're also the more distant stations. Most other GreenCube stations appeared to have less sophisticated antennas but are also using preamplifiers mounted at the antenna, which we decided we needed.
The other issue was that that the transmitted signal frequently didn't seem to be heard by the satellite. The FT-847 is only rated at 20 watts output on 70 centimeters and ours seemed to be putting out significantly less power, which doesn't appear to be enough to create a reliable and readable signal at the satellite. From some online research we found that some other stations appeared to be using Icom IC-9700 transceivers that run 70 watts on 70 centimeters, so we decided we needed to upgrade to a more powerful radio.
A confounding problem also appeared to be finding the correct base frequency for transmitting. Setting PST Rotator to the published frequencies required adjustment to make the received audio frequency center around 1500 Hz. But what about the transmit frequency? We didn't know exactly where the satellite would be listening, and being off by several hundred Hertz could make us unreadable. Finally, we found a reference telling us to set both frequencies lower by about 800 Hz, which put the received frequency perfectly in line for decoding by Soundmodem and also appeared to create the correct transmit frequency to be decoded by the satellite.
Adding the preamp
Al KB2AYU came to our rescue on the receive issue with a mast-mounted preamplifier for 70 centimeters that he installed on the antenna boom. We installed the power injector at the feedline switch and found that the preamp significantly improved receive performance. That preamp was initially switched out of the line by sensing the RF; however we later were able to hard-switch it using a direct connection to the PTT output of the transceiver.
Replacing the 847 with the 991A
The issue of low power output was solved by replacing the FT-847 transceiver with a newer FT-991a radio from my personal station. Initially we had some COM port issues which we traced down to having defined a virtual COM port at the same location that Windows assigned to the standard COM port of the 991. We also found that the 991 appeared to significantly reduce the high frequency component of the audio signal when set in USB-DATA mode (we found this by using the calibration function in Soundmodem and looking at the output from the low and high tones, finding the high tone output being significantly reduced). We solved this by operating the radio in USB mode, not USB-DATA mode. The complication with this arrangement is that there is apparently no adjustment on the transceiver for the audio level coming in through the USB port, so we had to adjust this in Windows for the maximum level that would not kick in the ALC. Finally we decided that we had everything working as well as we could.
How does it work?
At this point the GreenCube station seems to work as well as we could possibly expect. We can decode signals virtually throughout the entire pass and can view our transmitted signals on the downlink most of the time. At this point we've worked 38 different countries on five continents, with the longest distance QSO being 11,000 kilometers between us and the station in Japan. We're hopeful to work satellite DXCC although we're not confident that there are actually 100 operational GreenCube stations within the potential footprint of the satellite from our location.
But so far working this satellite has been an exciting new challenge, allowing us to learn much about how our equipment operates and how to create success on a digital half duplex satellite. We are planning to continue active operation on this satellite, so if you see W2MMD please give us a shout.
That's One High Tech Way Of Chasing DX!
By Jim Wright, N2GXJ
ADIF logs from the Satellite station at W2MMD through mid-March were recently uploaded to LoTW and eQSL. Oh my! Check out all the new countries confirmed now towards SAT DXCC at LoTW!
Recently confirmed :
And that's just in the last month!
LoTW DXCC SAT total: 21 (as of 3/17/23).
That's one high tech way of chasing DXCC!
By Jim Wright, N2GXJ
ADIF logs from the Satellite station at W2MMD through mid-March were recently uploaded to LoTW and eQSL. Oh my! Check out all the new countries confirmed now towards SAT DXCC at LoTW!
Recently confirmed :
- KP3V (Puerto Rico)
- IK3ITB (Italy)
- FG8OJ (Guadeloupe)
- EA3B (Spain)
- XQ3SA (Chile)
- PY2RN (Brazil)
- LU3FCA (Argentina)
- HC2FG (Ecuador)
- G0ABI (England)
- 4A7L (Mexico)
- S57NML (Slovenia)
- RA9DA (Asiatic Russia)
- DK9JC (Germany)
- 4J6D (Azerbaijan)
- XE2YWH (Mexico)
- VA7TF (Canada)
- OZ9AAR (Denmark)
- CO8LY (Cuba)
And that's just in the last month!
LoTW DXCC SAT total: 21 (as of 3/17/23).
That's one high tech way of chasing DXCC!
eQSL card received from Italy, for a recent 2-way Satellite contact made from the W2MMD Clubhouse
Meteor Scatter QSOs At The Clubhouse
By Jon Pearce, WB2MNF
“Meteor scatter” sounds like an improbable method of communicating, but when Frank N3PUU emailed that there was a planned meteor shower on December 13 and he wanted to try it at the Clubhouse. John K2QA, John K2ZA, and I headed down to see what we could work. Perhaps bouncing radio signals off meteors would actually yield some QSOs, especially using the new digital mode of communication.
Meteor scatter is exactly what it sounds like - it’s transmitting a coded signal on a designated frequency and hoping that it will be reflected off a meteor and end up somewhere else. Most of this work is done on 6 or 2 meters, so it’s pretty easy to tell if you’re hearing a station directly or if the signal is being bounced off a meteor (if you’re hearing a station that’s distant you’re not hearing them directly on those bands). Signal strength is a clue as is the location of the transmitting station, but reflections from meteors are also quite short, so an actual meteor transmission may only be a few seconds long.
Meteor scatter work is done using the MSK144 protocol, another protocol coming from the shop of Nobel prize winner Joe Taylor K1JT and his team. Its technical details are beyond the scope of this article, mainly because they’re beyond the scope of my brain, but basically the protocol transmits continuous-phase frequency shift keying (FSK) in 144-bit frames and at tone frequencies of 1000 and 2000 Hz. That signal is then transformed by magic into a “offset quadrature phase-shift keying (OQPSK) with individual pulses shaped like the first half-period of a sine wave”, according to the WSJT documentation (https://bit.ly/3FRrSk3) for MSK144. The frames are compressed into 72 bits with each frame containing a 72-bit user message, an 8-bit cyclic redundancy check and 48 bits of error-correcting redundancy. Transmissions are clocked similarly to FT8, are 15 seconds long and start exactly on either even or odd points each minute. QSOs are managed automatically by the program – once you answer a CQ the program will continue the QSO until a successful end.
Frank brought along a 2-meter SSB radio which he hooked up to the 2 meter satellite antenna on a table in the VHF room. It doesn’t really matter which direction you point the antennas because you don’t know where the meteors will be, but most of the stations are west of us so he pointed west, loaded up WSJT on the laptop and started listening on 2 meters.
Meanwhile I had fortuitously planned to bring my Flex 3000 to the Clubhouse HF room to provide another option for HF operating and had installed the Firewire card in the HF room PC, connected the Flex to the antenna switch and loaded the PowerSDR software. The Flex works on 6 meters so we tried a couple of the HF antennas and found that the 80 meter dipole worked best.
So now we had two stations running MSK144 - how did we do? On 6 meters it took some fiddling around with parameters but we finally got reliable decodes on several stations as shown in Figure 2. Since their signals were constant for the 15 second transmission we knew that we were hearing them directly, not bounced off of a meteor. But you’ll see in the screenshot in Figure 2 that we got lucky to see both sides of a QSO between Bill Booth VE3NXK of Ontario, Canada and John Price WA2FZW of Plainfield, NJ. Later that evening we saw several more QSOs on 6 meters so the evening was a success. The Flex wasn’t set up to transmit yet (I have to get the COM ports worked out for CAT control and PTT) so we couldn’t transmit, and the 80 meter dipole probably wouldn’t work well on 6 meters anyway.
Frank also had success on 2 meters, copying a number of station direct and reflected off meteors. He wasn’t able to create any QSO, however.
Was it a success?
For me it was - I had never seen this mode before and was surprised that we could copy anything reflected from a meteor. The 6 meter station using the 80 meter dipole worked surprisingly well but once we get a 6 meter beam up on the new tower we expect to have much better success.
So we’ll be watching for the next major meteor shower, which will be the Quadrantids shower that maxes on January 3, 2023, followed by the Lyrids shower on April 22, 2023.
Go to : https://bit.ly/3BDLOFJ for a schedule of meteor showers for 2023.
Now that we know what we’re doing we’ll make a broader announcement before those events so that others can participate.
By Jon Pearce, WB2MNF
“Meteor scatter” sounds like an improbable method of communicating, but when Frank N3PUU emailed that there was a planned meteor shower on December 13 and he wanted to try it at the Clubhouse. John K2QA, John K2ZA, and I headed down to see what we could work. Perhaps bouncing radio signals off meteors would actually yield some QSOs, especially using the new digital mode of communication.
Meteor scatter is exactly what it sounds like - it’s transmitting a coded signal on a designated frequency and hoping that it will be reflected off a meteor and end up somewhere else. Most of this work is done on 6 or 2 meters, so it’s pretty easy to tell if you’re hearing a station directly or if the signal is being bounced off a meteor (if you’re hearing a station that’s distant you’re not hearing them directly on those bands). Signal strength is a clue as is the location of the transmitting station, but reflections from meteors are also quite short, so an actual meteor transmission may only be a few seconds long.
Meteor scatter work is done using the MSK144 protocol, another protocol coming from the shop of Nobel prize winner Joe Taylor K1JT and his team. Its technical details are beyond the scope of this article, mainly because they’re beyond the scope of my brain, but basically the protocol transmits continuous-phase frequency shift keying (FSK) in 144-bit frames and at tone frequencies of 1000 and 2000 Hz. That signal is then transformed by magic into a “offset quadrature phase-shift keying (OQPSK) with individual pulses shaped like the first half-period of a sine wave”, according to the WSJT documentation (https://bit.ly/3FRrSk3) for MSK144. The frames are compressed into 72 bits with each frame containing a 72-bit user message, an 8-bit cyclic redundancy check and 48 bits of error-correcting redundancy. Transmissions are clocked similarly to FT8, are 15 seconds long and start exactly on either even or odd points each minute. QSOs are managed automatically by the program – once you answer a CQ the program will continue the QSO until a successful end.
Frank brought along a 2-meter SSB radio which he hooked up to the 2 meter satellite antenna on a table in the VHF room. It doesn’t really matter which direction you point the antennas because you don’t know where the meteors will be, but most of the stations are west of us so he pointed west, loaded up WSJT on the laptop and started listening on 2 meters.
Meanwhile I had fortuitously planned to bring my Flex 3000 to the Clubhouse HF room to provide another option for HF operating and had installed the Firewire card in the HF room PC, connected the Flex to the antenna switch and loaded the PowerSDR software. The Flex works on 6 meters so we tried a couple of the HF antennas and found that the 80 meter dipole worked best.
So now we had two stations running MSK144 - how did we do? On 6 meters it took some fiddling around with parameters but we finally got reliable decodes on several stations as shown in Figure 2. Since their signals were constant for the 15 second transmission we knew that we were hearing them directly, not bounced off of a meteor. But you’ll see in the screenshot in Figure 2 that we got lucky to see both sides of a QSO between Bill Booth VE3NXK of Ontario, Canada and John Price WA2FZW of Plainfield, NJ. Later that evening we saw several more QSOs on 6 meters so the evening was a success. The Flex wasn’t set up to transmit yet (I have to get the COM ports worked out for CAT control and PTT) so we couldn’t transmit, and the 80 meter dipole probably wouldn’t work well on 6 meters anyway.
Frank also had success on 2 meters, copying a number of station direct and reflected off meteors. He wasn’t able to create any QSO, however.
Was it a success?
For me it was - I had never seen this mode before and was surprised that we could copy anything reflected from a meteor. The 6 meter station using the 80 meter dipole worked surprisingly well but once we get a 6 meter beam up on the new tower we expect to have much better success.
So we’ll be watching for the next major meteor shower, which will be the Quadrantids shower that maxes on January 3, 2023, followed by the Lyrids shower on April 22, 2023.
Go to : https://bit.ly/3BDLOFJ for a schedule of meteor showers for 2023.
Now that we know what we’re doing we’ll make a broader announcement before those events so that others can participate.
Have You Tried A Flying Repeater?
By Jim Wright, N2GXJ
It can be challenging enough to set up your hand-held radio to work the local repeaters, either stationary or mobile. But have you tried to hit a mobile moving repeater? How about a repeater that is flying by? How about one that is flying by at the speed of 4.76 miles per second?
If you’re looking for the next challenge with your HT, here it is!
You know what I’m talking about, right? The email from our Club’s Jon Pearce (WB2MNF) Titled “Cross-band repeater now operational on the ISS!”. Club member Jeff Garth (WB2ZBN) replied saying he has heard it on his FM handheld. As Jeff describes, “I heard it! An HT tuned to 437.800 MHz. For about 4-5 minutes in my backyard, I heard call signs. And for about a minute, they came in very clear, but disappeared very quickly.”
As Jeff mentions, downlink to hear it is on 437.800 FM. Hint : listen a little higher early, lower later (Doppler shift). For those wanting an even greater challenge of making a 2-way contact through this repeater, the uplink is on 145.990 MHz where you’ll need to use a transmit-only CTCSS tone of 67 Hz. Has anyone else tried?
If interested in knowing more, there are several sources, here’s one :
https://amsat-uk.org/2020/09/02/iss-fm-repeater-activated/
Good luck if you dare to try!
By Jim Wright, N2GXJ
It can be challenging enough to set up your hand-held radio to work the local repeaters, either stationary or mobile. But have you tried to hit a mobile moving repeater? How about a repeater that is flying by? How about one that is flying by at the speed of 4.76 miles per second?
If you’re looking for the next challenge with your HT, here it is!
You know what I’m talking about, right? The email from our Club’s Jon Pearce (WB2MNF) Titled “Cross-band repeater now operational on the ISS!”. Club member Jeff Garth (WB2ZBN) replied saying he has heard it on his FM handheld. As Jeff describes, “I heard it! An HT tuned to 437.800 MHz. For about 4-5 minutes in my backyard, I heard call signs. And for about a minute, they came in very clear, but disappeared very quickly.”
As Jeff mentions, downlink to hear it is on 437.800 FM. Hint : listen a little higher early, lower later (Doppler shift). For those wanting an even greater challenge of making a 2-way contact through this repeater, the uplink is on 145.990 MHz where you’ll need to use a transmit-only CTCSS tone of 67 Hz. Has anyone else tried?
If interested in knowing more, there are several sources, here’s one :
https://amsat-uk.org/2020/09/02/iss-fm-repeater-activated/
Good luck if you dare to try!
W2MMD’s First Satellite Contact in Europe!
By Jon Pearce, WB2MNF
For those unfamiliar with satellite operation, working DX is quite different from terrestrial radio. Band conditions don't really matter since the stations that can be worked all must be within the footprint of the satellite. The satellite footprint is determined by the altitude of the satellite above the earth. It's like shining a flashlight on a basketball - the further away the satellite is, the larger the circle - but the circle is also dimmer because the same amount of light is spread through a larger area. This is how satellites work - satellites with lower orbits have less range than those with higher orbits.
The CAS-4A and -4B satellites (both launched from the same rocket) are in an orbit about 325 miles from earth and have a footprint that would cover most of the US if the satellite was located in the middle of the country. For east coast stations like W2MMD in NJ we can only work west-coast stations on passes over the middle of the country in which the east and west coasts are within the footprint - and then only for the few minutes before the satellite and the footprint move east and western stations are no longer within the footprint. On passes to the east of NJ there's little opportunity to work anyone since there are few hams in the middle of the Atlantic Ocean and the footprint isn't large enough to reach Europe because these satellites' orbits are too low. So the strategy for working "US DX" is to watch for passes in which the satellite is far to the west of NJ and madly try to work west-coast stations before the satellite slips below their horizon. Below is a picture of CAS-4B's footprint over Australia - you can see that it would just about cover the US.
By Jon Pearce, WB2MNF
For those unfamiliar with satellite operation, working DX is quite different from terrestrial radio. Band conditions don't really matter since the stations that can be worked all must be within the footprint of the satellite. The satellite footprint is determined by the altitude of the satellite above the earth. It's like shining a flashlight on a basketball - the further away the satellite is, the larger the circle - but the circle is also dimmer because the same amount of light is spread through a larger area. This is how satellites work - satellites with lower orbits have less range than those with higher orbits.
The CAS-4A and -4B satellites (both launched from the same rocket) are in an orbit about 325 miles from earth and have a footprint that would cover most of the US if the satellite was located in the middle of the country. For east coast stations like W2MMD in NJ we can only work west-coast stations on passes over the middle of the country in which the east and west coasts are within the footprint - and then only for the few minutes before the satellite and the footprint move east and western stations are no longer within the footprint. On passes to the east of NJ there's little opportunity to work anyone since there are few hams in the middle of the Atlantic Ocean and the footprint isn't large enough to reach Europe because these satellites' orbits are too low. So the strategy for working "US DX" is to watch for passes in which the satellite is far to the west of NJ and madly try to work west-coast stations before the satellite slips below their horizon. Below is a picture of CAS-4B's footprint over Australia - you can see that it would just about cover the US.
By contrast the recently-activated RS-44 satellite is in an elliptical orbit about 800-950 miles above the earth and consequently has a much larger footprint. That satellite has great potential for an east-coast station to work stations in Europe, Africa and South America depending on the position of the satellite over the earth. So there's significant strategy involved in planning which passes to try to work - eastern passes provide the greatest opportunity for Europe, but we also need to consider the time difference since evening passes in the US are late at night in Europe and few operators are on the air. A perfect pass is an eastern pass in the morning, and those are the ones that we wait for and try to operate.
A few weeks ago there was an eastern pass in which the footprint stretched all the way from NJ to Europe. On that morning I heard a station calling CQ as the satellite moved above the horizon (at Acquisition of Signal, or AOS) and realized that it be north of me since the footprint wasn't yet covering stations to the south. I could copy the suffix of the call as "SQL" but couldn't understand the prefix. It took three CQs for me to finally get the call as 2M0SQL in the UK. Finally - a station in Europe! Since the satellite is essentially a SSB repeater and the W2MMD station has those new wonderful M2 antennas we could copy each other perfectly and I noted that he was our first European QSO. He graciously offered a QSL card and a few minutes later tweeted about our QSO.
Studying the orbits of satellites gives great information about the potential for working new areas of the world and is important in designing an effective operating strategy. Simply working every pass is fun but is unlikely to create new grid squares. Using an orbit prediction program and planning operating sessions based on the optimal passes is more likely to result in fascinating QSOs like this one.
Satellite Antenna Upgrade At The W2MMD Clubhouse
By Jon Pearce, WB2MNF
The Clubhouse satellite station has had steady incremental upgrades over the past few years but one factor had remained constant - the antenna and rotator system. The antennas were 1980’s style Cushcraft units that were probably average at the time and gave reasonable but not outstanding performance. Since “outstanding” is a goal of the Skunkworks team we were able to procure through a Club member donation a pair of M2 state-of-the-art satellite antennas - the 42-element 436CP42UG crossed Yagi for 70 cm and the 22 element 2MCP22 crossed Yagi for 2 meters along with the fiberglass boom to connect them. These are the top of the line satellite antennas from M2 and promised to significantly improve Clubhouse satellite operations.
Both antennas are 18 feet long and have considerable gain and would be a significant improvement over the existing antennas but the additional length created potential problems in clearing the Clubhouse roof and the guy wires for the 6 meter beam so some initial planning was necessary before the antennas arrived. Al KB2AYU did some initial measurements from the roof of the Clubhouse and concluded that the mast for the antennas needed to be lengthened to provide enough clearance so he obtained a length of pipe of the correct length. He and Frank N3PUU were able to remove the old antennas and rotator from the mast and string new hardline and rotator cables to the tower before the new antennas were completed.
The new antennas required significant assembly - 42 elements is a LOT of building, especially when a millimeter of error can blow the efficiency of the antennas. Al painstakingly assembled each section of both antennas, carefully measuring each element to be sure that it was inserted correctly. In most Yagi antennas the director elements decrease in length along the boom, but in these antennas a director might be longer than the previous element so each element needed to be carefully measured down to 1/16 inch. And two elements weren’t cut to the specified length so Al had to build them from other materials. To make it even more difficult the assembled antennas were 18 feet long in three 6-foot sections so they couldn’t be completely assembled in the Clubhouse - they had to be finished off outside along with the vertical elements of the 2 meter antenna that wouldn’t fit out the Clubhouse door if assembled. Frank and Al assembled the sections outside using aluminum grease.
Finally the antennas were assembled and sitting on sawhorses outside of the shed. At that point Frank and Al noticed that the pre-drilled holes for the mounting plate provided by M2 would align that plate in line with the antenna elements, destroying their directivity. That problem was even noted in the assembly directions, which advised that the assembler could drill his own holes if he didn’t like it. The problem, of course, was that drilling a perfectly-centered hole through a pipe resting on sawhorses is pretty difficult so Frank designed and 3D-printed a drilling jig that would fit over the mast, lock into the existing holes and provide guide holes for a perfectly-aligned 45 degree mounting plate. There seems to be no problem that Frank can’t solve with his back-yard machine shop.
Once that was done it was time to mount them, but there’s no way that antennas of that size could be mounted without a bucket truck. Fortunately new GCARC member Dave KB3VEQ had shown up at Field Day with his own bucket truck and was willing to bring it out for this project. (Any ham who owns a bucket truck should never have to buy beer again…) Dave mounted the rotator, ran the boom thru the elevation rotator and then fastened each antenna to the end of the boom. He then connected the cables to the rotator and antennas - and we thought we were ready to go. Not so fast…
The test needed one guy in the Clubhouse (me) with an HT to rotate the antennas on command of the guys who were outside. After searching thru all of our Clubhouse gear we were able to scrounge up a couple of
HTs (what kind of hams don’t all have HTs hanging from their belts???) and we were ready for the test. I was given the command to raise the elevation of the antennas, which was followed almost immediately by the command “STOP!”. Walking outside and looking up I saw the antenna array pointing 10 degrees - towards the ground! We had carefully executed each step - except for figuring out which side of the boom the antennas should face. Obviously the boom rotates horizontally in the elevation rotator with one side rising and the other side falling, and we had the antennas facing to the falling side. Amidst laughter, groans and trying to figure out geometry with our fingers we instructed Dave to remove the antennas and replace them at different ends of the boom. And our frustration was compounded when that arrangement ALSO aimed the antennas into the ground. That prompted another round of drawing geometric shapes in the air with KB2AYU, K2QA, N3PUU and WB2MNF all thinking that they had finally figured out the right way to orient the antennas so that they would point up instead of down. The third time was the charm, with the antenna finally rising in accordance with the rotator controller. The new cable arrangement required longer coax connections between the antennas and the hardline so Al made them overnight and installed them a day later. At that point things looked really good and I was able to make a few contacts on subsequent satellite passes.
In the following couple of days I did some testing from home using the new antennas (connecting thru the VPN to the rotator and SDR servers) and found that the 70 cm antenna was much improved but the 2 meter antenna wasn’t performing well. So I went out to the Clubhouse and found that the 2 meter antenna has slipped on the boom and was now facing at about 45 degrees above the desired elevation. Aligning the antennas with the Clubhouse roof and climbing up onto the roof I was able to push it back into alignment but it didn’t stay - the weight of the feedline dragged down the back of the antenna. Frank and Al were able to tighten the boom bolts a couple of days later and it now stays in alignment.
And it seems to be working really well! On Thursday evening I was able to make 7 satellite contacts in a couple of hours during which there were several satellite passes. Signals from our station and other stations were strong in the downlink, indicating that the both antennas are working well.
There are still some final necessary adjustments but the station is now fully operational. So if you want to work some satellites email me (wb2mnf at arrl dot net) and we’ll find a time to get together when some satellites will be overhead.
By Jon Pearce, WB2MNF
The Clubhouse satellite station has had steady incremental upgrades over the past few years but one factor had remained constant - the antenna and rotator system. The antennas were 1980’s style Cushcraft units that were probably average at the time and gave reasonable but not outstanding performance. Since “outstanding” is a goal of the Skunkworks team we were able to procure through a Club member donation a pair of M2 state-of-the-art satellite antennas - the 42-element 436CP42UG crossed Yagi for 70 cm and the 22 element 2MCP22 crossed Yagi for 2 meters along with the fiberglass boom to connect them. These are the top of the line satellite antennas from M2 and promised to significantly improve Clubhouse satellite operations.
Both antennas are 18 feet long and have considerable gain and would be a significant improvement over the existing antennas but the additional length created potential problems in clearing the Clubhouse roof and the guy wires for the 6 meter beam so some initial planning was necessary before the antennas arrived. Al KB2AYU did some initial measurements from the roof of the Clubhouse and concluded that the mast for the antennas needed to be lengthened to provide enough clearance so he obtained a length of pipe of the correct length. He and Frank N3PUU were able to remove the old antennas and rotator from the mast and string new hardline and rotator cables to the tower before the new antennas were completed.
The new antennas required significant assembly - 42 elements is a LOT of building, especially when a millimeter of error can blow the efficiency of the antennas. Al painstakingly assembled each section of both antennas, carefully measuring each element to be sure that it was inserted correctly. In most Yagi antennas the director elements decrease in length along the boom, but in these antennas a director might be longer than the previous element so each element needed to be carefully measured down to 1/16 inch. And two elements weren’t cut to the specified length so Al had to build them from other materials. To make it even more difficult the assembled antennas were 18 feet long in three 6-foot sections so they couldn’t be completely assembled in the Clubhouse - they had to be finished off outside along with the vertical elements of the 2 meter antenna that wouldn’t fit out the Clubhouse door if assembled. Frank and Al assembled the sections outside using aluminum grease.
Finally the antennas were assembled and sitting on sawhorses outside of the shed. At that point Frank and Al noticed that the pre-drilled holes for the mounting plate provided by M2 would align that plate in line with the antenna elements, destroying their directivity. That problem was even noted in the assembly directions, which advised that the assembler could drill his own holes if he didn’t like it. The problem, of course, was that drilling a perfectly-centered hole through a pipe resting on sawhorses is pretty difficult so Frank designed and 3D-printed a drilling jig that would fit over the mast, lock into the existing holes and provide guide holes for a perfectly-aligned 45 degree mounting plate. There seems to be no problem that Frank can’t solve with his back-yard machine shop.
Once that was done it was time to mount them, but there’s no way that antennas of that size could be mounted without a bucket truck. Fortunately new GCARC member Dave KB3VEQ had shown up at Field Day with his own bucket truck and was willing to bring it out for this project. (Any ham who owns a bucket truck should never have to buy beer again…) Dave mounted the rotator, ran the boom thru the elevation rotator and then fastened each antenna to the end of the boom. He then connected the cables to the rotator and antennas - and we thought we were ready to go. Not so fast…
The test needed one guy in the Clubhouse (me) with an HT to rotate the antennas on command of the guys who were outside. After searching thru all of our Clubhouse gear we were able to scrounge up a couple of
HTs (what kind of hams don’t all have HTs hanging from their belts???) and we were ready for the test. I was given the command to raise the elevation of the antennas, which was followed almost immediately by the command “STOP!”. Walking outside and looking up I saw the antenna array pointing 10 degrees - towards the ground! We had carefully executed each step - except for figuring out which side of the boom the antennas should face. Obviously the boom rotates horizontally in the elevation rotator with one side rising and the other side falling, and we had the antennas facing to the falling side. Amidst laughter, groans and trying to figure out geometry with our fingers we instructed Dave to remove the antennas and replace them at different ends of the boom. And our frustration was compounded when that arrangement ALSO aimed the antennas into the ground. That prompted another round of drawing geometric shapes in the air with KB2AYU, K2QA, N3PUU and WB2MNF all thinking that they had finally figured out the right way to orient the antennas so that they would point up instead of down. The third time was the charm, with the antenna finally rising in accordance with the rotator controller. The new cable arrangement required longer coax connections between the antennas and the hardline so Al made them overnight and installed them a day later. At that point things looked really good and I was able to make a few contacts on subsequent satellite passes.
In the following couple of days I did some testing from home using the new antennas (connecting thru the VPN to the rotator and SDR servers) and found that the 70 cm antenna was much improved but the 2 meter antenna wasn’t performing well. So I went out to the Clubhouse and found that the 2 meter antenna has slipped on the boom and was now facing at about 45 degrees above the desired elevation. Aligning the antennas with the Clubhouse roof and climbing up onto the roof I was able to push it back into alignment but it didn’t stay - the weight of the feedline dragged down the back of the antenna. Frank and Al were able to tighten the boom bolts a couple of days later and it now stays in alignment.
And it seems to be working really well! On Thursday evening I was able to make 7 satellite contacts in a couple of hours during which there were several satellite passes. Signals from our station and other stations were strong in the downlink, indicating that the both antennas are working well.
There are still some final necessary adjustments but the station is now fully operational. So if you want to work some satellites email me (wb2mnf at arrl dot net) and we’ll find a time to get together when some satellites will be overhead.
Gloucester Co ARC In Club Competition For The January VHF Contest
By Jim Wright, N2GXJ
During the third weekend in January, some of your Club members banded together as a team to enter a club score for Gloucester Co ARC during the ARRL’s January VHF contest. Some members operated together as a multi-op station from the Clubhouse, while others contributed their individual scores from their home stations in our local area for a combined team score. How good did we do compared with other clubs in this category? We’ll just have to wait until the scores are published to see. But it really doesn’t matter, as it was billed as a learning experience, and the key was we all had fun. But even with all those caveats, I think we might have done quite well! Given the radio conditions, our combined score certainly exceeded my expectations!
Burning up the airwaves from the Clubhouse on 4 different bands, from a dedicated 6 meter station, and a separate “2 meters and up” station, were Al KB2AYU, John K2QA, Herb KT2Y, Frank N3PUU, and myself N2GXJ. Coincidentally, at the other end of the Clubhouse, Bruce KD2LBU was making separate contacts on HF for fun, as part of the North American QSO Party which overlapped with the VHF contest on Saturday night. Though it was snowing Saturday night, that didn’t stop a number of people from dropping in at the Clubhouse that evening, making it quite the place to be! And the food… a special thank you to Frank and his wife for the dinner at the Clubhouse Saturday night, and for the pot of chili that kept us warm the next day!
Putting in fantastic home station efforts for the VHF contest were Sheldon K2MEN and Mark KK2L, who had also pre-registered with the ARRL to be able to submit scores naming Gloucester Co ARC as their home club as part of this combined team effort. Thanks guys!
And then there was Jim KD2QYE and Lee ND2G. Did I happen to mention that it was snowing Saturday night? Let me copy here an email received from Jim to indicate why that’s relevant :
“Lee and I set up portable at a location about 2 miles from the Club in Heritages vineyard. It's elevation was around 150 feet above sea level. We set up Lee's Kenwood TS-590sg for 6m with a Shark 44" 6m antenna on a 20' mast off the hitch of my pickup. We then switch radios to my Yaesu FTM-400 XDR and used a J-Pole I made from 1/2" copper pipe on a 10' mast for VHF. See attached for the contacts we made. I hope this helps the Club! Great day in the snow for my first contest, Jim KD2QYE”
Now that’s the crazy spirit! First contest - portable - outside in a SNOWSTORM, no less. Wow! Congratulations you guys! You know, there is a big event called Field Day each year, in June, where we set up as many stations as we can in the fields around our Clubhouse to make contacts with other clubs doing the same thing all over the USA and Canada that weekend. Maybe you, and others reading this article, might be interested in participating and helping our Club score in that event too? By June, it should be a little warmer!
Thank you again for the fun times in this contest. Hope to catch everyone next when we try and find the hidden transmitter that Frank is going to hide during the next fox hunt!
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December 28, 2019
“The Clubhouse now has a big 6 Meter Yagi antenna (30ft boom length) up on a 40ft mast. It was a perfect day for the job with mild temperatures and almost no wind. Big thanks to Frank, N3PUU for many hours of help getting all the hardware in place and assembled. Thanks also to Bruce KD2LBU and Jon WB2MNF who were pressed into service working the guy ropes as the mast was raised into position. There is still a lot to do in the VHF radio room to get everything hooked up and running smoothly.” Al KB2AYU
“The Clubhouse now has a big 6 Meter Yagi antenna (30ft boom length) up on a 40ft mast. It was a perfect day for the job with mild temperatures and almost no wind. Big thanks to Frank, N3PUU for many hours of help getting all the hardware in place and assembled. Thanks also to Bruce KD2LBU and Jon WB2MNF who were pressed into service working the guy ropes as the mast was raised into position. There is still a lot to do in the VHF radio room to get everything hooked up and running smoothly.” Al KB2AYU
SWLing Satellites With No Radio Equipment
By Jon Pearce, WB2MNF
By Jon Pearce, WB2MNF
With the plethora of new rocket technology these days it seems that someone is launching interesting new satellites every couple of days. Many of these are “microsats” the size of a Rubik’s cube and can be popped off the top of a rocket or shot out a slot on the International Space Station a half-dozen satellites at a time. Some are ham communications satellites that will allow FM or SSB communication, or will support APRS or PSK communication, while many others send down telemetry or images such as the recent SSTV transmissions from the ISS. Part of the fun of operating these satellites is the radio part - getting the antennas pointed in the right spot in space, correcting for the Doppler frequency shift in the signals, and tuning in and decoding the signals, but not everyone has the equipment or home space for the multi-element antennas and az-el rotators that we’re fortunate enough to have at the W2MMD Clubhouse. Luckily for these folks there’s a way for them to have someone else download the audio from the satellites and store it in a data warehouse from which individual users can access it. This system is called “SatNOGS” and the W2MMD Clubhouse station is part of its network.
SatNOGS consists of a worldwide network of stations shown on Figure 1 below. These stations have a variety of antenna configurations but all utilize software-defined radios to download the audio signals from the satellites and upload those audio files in a lossless .OGG format to the central SatNOGS data warehouse. From that warehouse individual users can view the waterfall frequency displays of the satellites, download the audio and pipe it into various demodulation programs depending on the type of modulation used by the satellite. If the satellite is sending 1200 baud AFSK packets such as those commonly used in APRS, the audio is piped into a 1200 baud modem. If the signal is the ISS sending SSTV pictures a SSTV decoder is used. The “pipe” generally used is the “Virtual Audio Cable” program that uses software to connect the audio output of the signal source to the decoding software. It works like a physical cable connecting a radio with a modem, except that the “radio” and “modem” are really programs running within the same computer.
SatNOGS consists of a worldwide network of stations shown on Figure 1 below. These stations have a variety of antenna configurations but all utilize software-defined radios to download the audio signals from the satellites and upload those audio files in a lossless .OGG format to the central SatNOGS data warehouse. From that warehouse individual users can view the waterfall frequency displays of the satellites, download the audio and pipe it into various demodulation programs depending on the type of modulation used by the satellite. If the satellite is sending 1200 baud AFSK packets such as those commonly used in APRS, the audio is piped into a 1200 baud modem. If the signal is the ISS sending SSTV pictures a SSTV decoder is used. The “pipe” generally used is the “Virtual Audio Cable” program that uses software to connect the audio output of the signal source to the decoding software. It works like a physical cable connecting a radio with a modem, except that the “radio” and “modem” are really programs running within the same computer.
Figure 1 : SatNOGS Station Network
Each station on the SatNOGS network has a home page showing information about the station, the observations that the station has recorded and a list of upcoming satellite passes at that station’s location. The home page for the W2MMD station is shown Figure 2 below and is at https://network.satnogs.org/stations/223. From that page users can navigate to the blue Observations button to display the past and future satellite observations for that station, which is shown in Figure 3 below.
Figure 3 shows that many observations for upcoming SSTV passes from the ISS were scheduled since the ISS was broadcasting SSTV when this screenshot was taken. At the scheduled time the program running on the Clubhouse Raspberry Pi SatNOGS computer will set the attached RTL-SDR receiver to the Doppler-corrected frequency, command the station 2-meter Yagi antenna to track the satellite as it moved through the sky and will start recording the audio on that frequency. It will record throughout that pass and upload the resulting audio file to the SatNOGS warehouse.
Figure 2 : W2MMD SatNOGS Home Page
Figure 3 : Observations by W2MMD
The passes indicated by yellow and green boxes occurred in the past and their results are available on observations screens for the respective observations. One of those screens is shown in Figure 4 below. This shows the time of the pass, the maximum elevation and azimuth, and the location of the orbit in the graphic. The waterfall shows the Doppler-corrected signal, which in this case is a SSTV signal. The “Audio” tab will allow the user to play back the audio and listen to it, and the “Data” tab will show the decoded data if SatNOGS has a decoder for that type of transmission (which it doesn’t have for SSTV signals).
Figure 4 : ISS SSTV Observation
On that screen you’ll also notice that the pass was requested by Fredy Dankalis, who’s part of the SatNOGS development team in Greece. This shows that other members of the SatNOGS network can program stations other than their own to record passes. In this case Fredy apparently wants to get all of the SSTV passes and has probably requested many ground stations to record these passes. By default any SatNOGS operator can program any SatNOGS station, which allows satellite managers to record telemetry from their satellites even at remote locations around the earth.
Of special interest to the experimenter on the Figure 4 screen is the “Download“ button for the audio, which is on the lower left of the screen below the concentric circles showing the geometry of the satellite pass. This allows the experimenter to download the audio file as an .OGG file to their computer. In the case of a SSTV signal this would download the SSTV audio. OGG files can be opened natively in Audacity , a shareware program used for audio editing, and an SSTV pass looks like Figure 5 below. Note that the output of Audacity is being directed to “Line 4” of a virtual audio cable, which will virtually connect it to the decoder program.
Of special interest to the experimenter on the Figure 4 screen is the “Download“ button for the audio, which is on the lower left of the screen below the concentric circles showing the geometry of the satellite pass. This allows the experimenter to download the audio file as an .OGG file to their computer. In the case of a SSTV signal this would download the SSTV audio. OGG files can be opened natively in Audacity , a shareware program used for audio editing, and an SSTV pass looks like Figure 5 below. Note that the output of Audacity is being directed to “Line 4” of a virtual audio cable, which will virtually connect it to the decoder program.
Figure 5 : Audacity SSTV File
Finally we use the MMTV program (Figure 6) to decode the SSTV audio signal as it’s played in Audacity. This occurs in real-time - the audio is played back at the same speed at which it was originally recorded from the ISS and the decoding occurs simultaneously. And while we’re using MMTV to decode the SSTV signal, the actual decoder will be determined by the type of signal being decoded. A 9600 baud GMSK digital signal would be decoded using the UZ7HO high-speed SoundModem program, while the PSK signal from NO-84 would use FL-Digi. CW telemetry could also be decoded by FL-Digi - or by the ear of an experienced CW operator.
Figure 6 : MMTV Decoding SSTV
So while the real fun in satellite operating is actually receiving the signals live from the satellite, that’s not always possible because of equipment or time constraints, but using SatNOGS allows experimenters to learn how satellite modulation schemes work and to work with satellite telemetry and other signals that they otherwise wouldn’t be able to access. It provides yet another opportunity to explore the great hobby of ham radio.
Building The Raspberry Pi NOAA Satellite Station
By Jon Pearce, WB2MNF
After building the station to receive the GOES geostationary weather satellite, constructing the NOAA satellite station was a relative breeze. The NOAA series of satellites (NOAA 15, 18 and 19) are much more similar to amateur satellites than the GOES satellite - they operate in the 137 MHz band, are in low-earth orbits and transmit analog images rather than the complex error-corrected digital images of the GOES satellites. I simply followed the “Instructables” project design and it mostly worked the first time.
The overall concept is simple - the project uses a inexpensive RTL-SDR radio and a Raspberry Pi computer along with free software that you install on the Pi. There are several components to the software - first it uses the Gpredict program to set up times (cron jobs) for each satellite based on the next pass for each of the three satellites. At the scheduled time the Pi runs a script that will enable the RTL-SDR receiver, set it to the frequency for the respective satellite, and will pipe the output to the wxtoimg program that will record the output in a format to be processed. At the end of the pass the wxtoimg program will process the output into images based on the parameters given to that program. It will then schedule the next pass for that satellite and go dormant again until the next satellite pass.
Change to instructions
The instructions from the Instructables site were quite accurate and helpful, with one exception - they reference the original website for the wxtoimg software. But apparently the author of that software has disappeared, it’s no longer being supported and the original wxtoimg.com website no longer exists. That meant that anyone wanting to use this program (which is outstanding and apparently used by everyone decoding this data) had no place from which to download it. Fortunately a guy named Kevin Schuchmann created a site called WxToImg Restored with all of the code for downloading as well as the keys to unlock the premium versions of the programs. Therefore, when the Instructables instructions say to get the wxtoimg file here : wget http://www.wxtoimg.com/beta/wxtoimg-armhf-2.11.2-beta.deb
you need to instead use this site : wget https://wxtoimgrestored.xyz/beta/wxtoimg-armhf-2.11.2-beta.deb
Otherwise everything worked fine for me.
Image output
The program places the RTL-SDR output file and the decoded images in the /home/pi/weather folder, so that’s where you’ll find them for viewing. Sooner or later we’ll need to do some cleanup on that folder, but the images are pretty small so it’s not an immediate concern.
Although wxtoimg can produce multiple decoded images from the downloaded data the Instructables project only used one of them. K2QA and I played around with the Windows version of the program and its output and figured out a couple of additional command line options that can be added to produce additional images. They’re shown in the script in Figure 1, which is in the /home/pi/weather/predict folder. These produce the images in Figure 2, Figure 3 and Figure 4.
Adding pictures to the website
Viewing the images on the Pi is a little cumbersome so we wrote a script to find the most recent of each picture file type and copy it into a folder from which it could be viewed on a website (you’ll need to install Apache on the Pi first). The script on page 20 will copy the most recent MCIR file into a file named current_mcir.png in the html folder from which it can be displayed on a web page.
That can be displayed by an HTML script like the one below :
<DOCTYPE html>
<html>
<head>
<title>W2MMD NOAA Pictures of the Day</title>
</head>
<body>
<h1>W2MMD NOAA Pictures of the Day</h1>
<img src="current_org.png" alt="POTD" height="800" width="800">
<img src="current_no.png" alt="POTD" height="800" width="800">
<img src="current_mcir.png" alt="POTD" height="800" width="800">
</body>
</html>
RF Hardware
Although the NOAA satellites use the 137 MHz frequencies they appear to be pretty readable using 2 Meter antennas, so we simply put a T connector in the feedline for the Lindenblad antenna used for our Fox-In-A-Box receiver and fed it to the RTL-SDR (the antenna has a mast-mounted broadband preamp so we didn’t worry about connector loss). That gave us decent but not exceptional pictures, but adding the SAW filter in front of the RTL-SRD receiver caused a significant increase in picture quality - almost all of the passes now generate very good images. Signals from these satellites are significantly stronger than from ham satellites (perhaps the US government has a higher satellite budget than AMSAT) so marginal antennas may still work well.
By Jon Pearce, WB2MNF
After building the station to receive the GOES geostationary weather satellite, constructing the NOAA satellite station was a relative breeze. The NOAA series of satellites (NOAA 15, 18 and 19) are much more similar to amateur satellites than the GOES satellite - they operate in the 137 MHz band, are in low-earth orbits and transmit analog images rather than the complex error-corrected digital images of the GOES satellites. I simply followed the “Instructables” project design and it mostly worked the first time.
The overall concept is simple - the project uses a inexpensive RTL-SDR radio and a Raspberry Pi computer along with free software that you install on the Pi. There are several components to the software - first it uses the Gpredict program to set up times (cron jobs) for each satellite based on the next pass for each of the three satellites. At the scheduled time the Pi runs a script that will enable the RTL-SDR receiver, set it to the frequency for the respective satellite, and will pipe the output to the wxtoimg program that will record the output in a format to be processed. At the end of the pass the wxtoimg program will process the output into images based on the parameters given to that program. It will then schedule the next pass for that satellite and go dormant again until the next satellite pass.
Change to instructions
The instructions from the Instructables site were quite accurate and helpful, with one exception - they reference the original website for the wxtoimg software. But apparently the author of that software has disappeared, it’s no longer being supported and the original wxtoimg.com website no longer exists. That meant that anyone wanting to use this program (which is outstanding and apparently used by everyone decoding this data) had no place from which to download it. Fortunately a guy named Kevin Schuchmann created a site called WxToImg Restored with all of the code for downloading as well as the keys to unlock the premium versions of the programs. Therefore, when the Instructables instructions say to get the wxtoimg file here : wget http://www.wxtoimg.com/beta/wxtoimg-armhf-2.11.2-beta.deb
you need to instead use this site : wget https://wxtoimgrestored.xyz/beta/wxtoimg-armhf-2.11.2-beta.deb
Otherwise everything worked fine for me.
Image output
The program places the RTL-SDR output file and the decoded images in the /home/pi/weather folder, so that’s where you’ll find them for viewing. Sooner or later we’ll need to do some cleanup on that folder, but the images are pretty small so it’s not an immediate concern.
Although wxtoimg can produce multiple decoded images from the downloaded data the Instructables project only used one of them. K2QA and I played around with the Windows version of the program and its output and figured out a couple of additional command line options that can be added to produce additional images. They’re shown in the script in Figure 1, which is in the /home/pi/weather/predict folder. These produce the images in Figure 2, Figure 3 and Figure 4.
Adding pictures to the website
Viewing the images on the Pi is a little cumbersome so we wrote a script to find the most recent of each picture file type and copy it into a folder from which it could be viewed on a website (you’ll need to install Apache on the Pi first). The script on page 20 will copy the most recent MCIR file into a file named current_mcir.png in the html folder from which it can be displayed on a web page.
- #!/bin/bash
- MCIR_FILE=$(ls -l /home/pi/weather | grep mcir | sed 's/^.*NOAA/NOAA/' | sort -k 1.7 | tail -1)
- cp /home/pi/weather/$MCIR_FILE /var/www/html/current_mcir.png
That can be displayed by an HTML script like the one below :
<DOCTYPE html>
<html>
<head>
<title>W2MMD NOAA Pictures of the Day</title>
</head>
<body>
<h1>W2MMD NOAA Pictures of the Day</h1>
<img src="current_org.png" alt="POTD" height="800" width="800">
<img src="current_no.png" alt="POTD" height="800" width="800">
<img src="current_mcir.png" alt="POTD" height="800" width="800">
</body>
</html>
RF Hardware
Although the NOAA satellites use the 137 MHz frequencies they appear to be pretty readable using 2 Meter antennas, so we simply put a T connector in the feedline for the Lindenblad antenna used for our Fox-In-A-Box receiver and fed it to the RTL-SDR (the antenna has a mast-mounted broadband preamp so we didn’t worry about connector loss). That gave us decent but not exceptional pictures, but adding the SAW filter in front of the RTL-SRD receiver caused a significant increase in picture quality - almost all of the passes now generate very good images. Signals from these satellites are significantly stronger than from ham satellites (perhaps the US government has a higher satellite budget than AMSAT) so marginal antennas may still work well.
APRS Weather From The W2MMD Clubhouse
By Jon Pearce, WB2MNF
“So now that we have a weather station at the Clubhouse, why aren’t we broadcasting real-time weather thru APRS?” said John Zaruba K2ZA one day, signaling the start of another GCARC Skunkworks project. The weather station (a topic for another article) was up and running and its output could be viewed from a web server on the Clubhouse network, but without a VPN connection to the Clubhouse (or being physically present there) nobody could see it. And the Clubhouse weather was getting increasingly important with the upcoming heat of summer since we wanted to monitor the temperature inside the satellite room because several computers are running 24/7 there. In addition, several of us are working with the Cooper Health System emergency communications team and planning to use APRS as a means to report from remote healthcare facilities, so it made sense for us to get familiar with creating customized APRS messages and figuring out how to transmit and monitor them over the air.
Hardware (Reference Figure 1)
The APRS station would require three pieces of hardware - a 2 Meter FM radio, a Raspberry Pi computer and a USB audio device to transfer the sound from the Pi to the radio. I had hoped that we could reuse one of two vintage 2 Meter FM radios (an IC-28H or an IC-27) that I had left over from the packet radio era in the 1980s, but the IC-28 started giving off a burning-component smell when powered up and the IC-27 didn’t appear to have any audio output so we had to pick up a FTM-3100 from HRO to get started. I connected it to a 2 Meter vertical that had been taking space in my garage for about 15 years and set it up temporarily on the Clubhouse “antenna testbed” (formerly known as a “picnic table”) until we can mount it on the mast at the west end of the Clubhouse.
The weather computer runs on its own Raspberry Pi, which is mounted on an acetate plate with all of the sensors and other components on the south wall of the satellite room. It samples the sensors every minute and writes the values to a log file. That log file is summarized by another Python program to develop the graphs as seen in Figure 2. At some future point we hope to link those graphs to the GCARC website. For APRS we elected to use that file and reformat it into the APRS beacon format.
The APRS function runs in Direwolf on another Pi. Direwolf handles the AX.25 packet formation and also populates the frame with the APRS data. By itself it provides full functionality for creating an APRS station. It feeds the audio through a USB port to an audio device that’s connected to the speaker and mic connections on the radio since the Pi only supports audio output, not audio input. Some designs use a cheap USB audio device with mic and speaker ports, but that doesn’t provide the PTT functionality needed for the radio. That’s why we used the more costly SignaLink that uses an internal VOX to create a PTT signal on the mic plug, but cheaper options are available that we’ll be exploring later.
Software
Direwolf conveniently will read APRS beacon text from either a text file or the output of a program, so we wrote a Python program that reformats the WX log file (which is copied from the WX Pi to the APRS Pi) into the format required by the APRS protocol. That translation took a while to get right, but it’s now working and the weather data is output in APRS beacons from W2MMD-13 that occur every 10 minutes. You can copy these beacons using an APRS-capable rig like a FTM-400 or FTx HT on 144.390 MHz. You can also see the beacons on aprs.fi. See Figures 3 and 4 for the web and iPhone visualizations from that site.
So far, so good - but we wanted more. Some of the metrics that we wanted to measure via APRS aren’t standard APRS weather measurements and don’t have a place in the weather protocol. For example, we want to measure the temperature inside the satellite room of the Clubhouse since if the temps get much higher than 95 degrees we’ll need to find a way to cool those computers. This gave us an opportunity to explore another facet of APRS, which is the ability to send telemetry in an APRS packet. We formatted the Clubhouse temperature along with the motion sensor reading and the lightning counter (the latter two aren’t yet functional) into the first three fields of a telemetry packet and set it up as a second beacon text, which is recognized as telemetry by Direwolf and aprs.fi. That seems to work OK, so we can now monitor the Clubhouse temperature from an HT or from the aprs.fi website. Pretty cool, eh?
Receiving telemetry (Reference Figures 2,3,4)
The above setup is one step in this project - the second step is creating a small, inexpensive simple receiver that can monitor the telemetry and alert the user to specific conditions. This has applications for the Clubhouse, but also has uses in our emergency communications project. Frank N3PUU pulled this together into a Raspberry Pi (about $35) using an RTL-SDR radio (about $21) with a small monitor or touch screen. Frank has this project running using Direwolf to receive and log the packets, a Python script to read the log file and monitor changes, and a json program to display it on a web server running on the Pi. This program can be parameterized to check for specific data values (for example if the Clubhouse temperature exceeds a specified value) and display a notification on the screen. We’ll be continuing to develop this capability, but the infrastructure is largely complete.
Next steps (Reference Figure 5)
After perusing the APRS specifications and the Direwolf documentation it’s evident that APRS is a powerful communication medium that we need to pursue. Our next project is to build an AC power sensor to notify if the Clubhouse power goes out. The APRS Pi and radio run from a UPS so they’ll stay online for a short period (about 15 minutes) after a power failure, which would give time for a few APRS notification beacons. To do this we need to connect a 5 volt power source (a wall-wart power cube) to an analog to digital converter (ADC) and then to the APRS Pi, and write the Python software that will check the voltage (we only care if it’s zero or non-zero). This will let us measure the 5V line and change a telemetry field in the beacon text if the power is off. This can be picked up by the simple receiver and create a notification on the screen. Of course, if the power is off for an extended period, the APRS transmissions will cease, but that could occur for several reasons other than a power failure so this will provide verification of the cause.
Also - a few of the Skunkworks team members have indicated interest in high-altitude balloon work possibly using the new PicoAPRS-Lite unit. This is a new project that may proceed slowly given that none of us have significant experience with ballooning, but such limitations only provide another opportunity to learn new stuff, which is one of the fun parts of being a ham.
By Jon Pearce, WB2MNF
“So now that we have a weather station at the Clubhouse, why aren’t we broadcasting real-time weather thru APRS?” said John Zaruba K2ZA one day, signaling the start of another GCARC Skunkworks project. The weather station (a topic for another article) was up and running and its output could be viewed from a web server on the Clubhouse network, but without a VPN connection to the Clubhouse (or being physically present there) nobody could see it. And the Clubhouse weather was getting increasingly important with the upcoming heat of summer since we wanted to monitor the temperature inside the satellite room because several computers are running 24/7 there. In addition, several of us are working with the Cooper Health System emergency communications team and planning to use APRS as a means to report from remote healthcare facilities, so it made sense for us to get familiar with creating customized APRS messages and figuring out how to transmit and monitor them over the air.
Hardware (Reference Figure 1)
The APRS station would require three pieces of hardware - a 2 Meter FM radio, a Raspberry Pi computer and a USB audio device to transfer the sound from the Pi to the radio. I had hoped that we could reuse one of two vintage 2 Meter FM radios (an IC-28H or an IC-27) that I had left over from the packet radio era in the 1980s, but the IC-28 started giving off a burning-component smell when powered up and the IC-27 didn’t appear to have any audio output so we had to pick up a FTM-3100 from HRO to get started. I connected it to a 2 Meter vertical that had been taking space in my garage for about 15 years and set it up temporarily on the Clubhouse “antenna testbed” (formerly known as a “picnic table”) until we can mount it on the mast at the west end of the Clubhouse.
The weather computer runs on its own Raspberry Pi, which is mounted on an acetate plate with all of the sensors and other components on the south wall of the satellite room. It samples the sensors every minute and writes the values to a log file. That log file is summarized by another Python program to develop the graphs as seen in Figure 2. At some future point we hope to link those graphs to the GCARC website. For APRS we elected to use that file and reformat it into the APRS beacon format.
The APRS function runs in Direwolf on another Pi. Direwolf handles the AX.25 packet formation and also populates the frame with the APRS data. By itself it provides full functionality for creating an APRS station. It feeds the audio through a USB port to an audio device that’s connected to the speaker and mic connections on the radio since the Pi only supports audio output, not audio input. Some designs use a cheap USB audio device with mic and speaker ports, but that doesn’t provide the PTT functionality needed for the radio. That’s why we used the more costly SignaLink that uses an internal VOX to create a PTT signal on the mic plug, but cheaper options are available that we’ll be exploring later.
Software
Direwolf conveniently will read APRS beacon text from either a text file or the output of a program, so we wrote a Python program that reformats the WX log file (which is copied from the WX Pi to the APRS Pi) into the format required by the APRS protocol. That translation took a while to get right, but it’s now working and the weather data is output in APRS beacons from W2MMD-13 that occur every 10 minutes. You can copy these beacons using an APRS-capable rig like a FTM-400 or FTx HT on 144.390 MHz. You can also see the beacons on aprs.fi. See Figures 3 and 4 for the web and iPhone visualizations from that site.
So far, so good - but we wanted more. Some of the metrics that we wanted to measure via APRS aren’t standard APRS weather measurements and don’t have a place in the weather protocol. For example, we want to measure the temperature inside the satellite room of the Clubhouse since if the temps get much higher than 95 degrees we’ll need to find a way to cool those computers. This gave us an opportunity to explore another facet of APRS, which is the ability to send telemetry in an APRS packet. We formatted the Clubhouse temperature along with the motion sensor reading and the lightning counter (the latter two aren’t yet functional) into the first three fields of a telemetry packet and set it up as a second beacon text, which is recognized as telemetry by Direwolf and aprs.fi. That seems to work OK, so we can now monitor the Clubhouse temperature from an HT or from the aprs.fi website. Pretty cool, eh?
Receiving telemetry (Reference Figures 2,3,4)
The above setup is one step in this project - the second step is creating a small, inexpensive simple receiver that can monitor the telemetry and alert the user to specific conditions. This has applications for the Clubhouse, but also has uses in our emergency communications project. Frank N3PUU pulled this together into a Raspberry Pi (about $35) using an RTL-SDR radio (about $21) with a small monitor or touch screen. Frank has this project running using Direwolf to receive and log the packets, a Python script to read the log file and monitor changes, and a json program to display it on a web server running on the Pi. This program can be parameterized to check for specific data values (for example if the Clubhouse temperature exceeds a specified value) and display a notification on the screen. We’ll be continuing to develop this capability, but the infrastructure is largely complete.
Next steps (Reference Figure 5)
After perusing the APRS specifications and the Direwolf documentation it’s evident that APRS is a powerful communication medium that we need to pursue. Our next project is to build an AC power sensor to notify if the Clubhouse power goes out. The APRS Pi and radio run from a UPS so they’ll stay online for a short period (about 15 minutes) after a power failure, which would give time for a few APRS notification beacons. To do this we need to connect a 5 volt power source (a wall-wart power cube) to an analog to digital converter (ADC) and then to the APRS Pi, and write the Python software that will check the voltage (we only care if it’s zero or non-zero). This will let us measure the 5V line and change a telemetry field in the beacon text if the power is off. This can be picked up by the simple receiver and create a notification on the screen. Of course, if the power is off for an extended period, the APRS transmissions will cease, but that could occur for several reasons other than a power failure so this will provide verification of the cause.
Also - a few of the Skunkworks team members have indicated interest in high-altitude balloon work possibly using the new PicoAPRS-Lite unit. This is a new project that may proceed slowly given that none of us have significant experience with ballooning, but such limitations only provide another opportunity to learn new stuff, which is one of the fun parts of being a ham.
May 22, 2019
The GCARC ‘Skunkworks’ committee (Mike KD2RPE, Frank N3PUU, Jon WB2MNF, John K2QA, and John K2ZA) met at Frank’s QTH for session of Lindenblad antenna construction
The GCARC ‘Skunkworks’ committee (Mike KD2RPE, Frank N3PUU, Jon WB2MNF, John K2QA, and John K2ZA) met at Frank’s QTH for session of Lindenblad antenna construction
W2MMD Satellite Station - September 20, 2018
By Jon Pearce, WB2MNF
If you’ve been to the Clubhouse over the past couple of weeks you may have seen the BBQ grill-type antenna that’s tie-wrapped to one of the picnic tables. That’s a 1.7 GHz antenna that we’re using to try to copy the images transmitted by the GOES series of weather satellites that are in geostationary orbit 23,600 miles above the equator. We’ve been challenged by issues with antenna aiming, working at microwave frequencies and rain, but K2QA and I finally achieved some success yesterday in copying high-res images from GOES-16. Checking the files shows about 700 more pictures downloaded from the satellite over the last 2 days.
GOES satellites transmit beautiful high-res shots of the entire earth, which we’re hoping to receive by leaving the decoder running (it runs on a Raspberry Pi), so hopefully by Tech Saturday we can show some more stunning images, but given that this satellite is further away than anything on Earth can possibly be, we are claiming the GCARC SWL DX record with these pix! More information is at the W2MMD Satellite Blog, if you’re interested in this project.
By Jon Pearce, WB2MNF
If you’ve been to the Clubhouse over the past couple of weeks you may have seen the BBQ grill-type antenna that’s tie-wrapped to one of the picnic tables. That’s a 1.7 GHz antenna that we’re using to try to copy the images transmitted by the GOES series of weather satellites that are in geostationary orbit 23,600 miles above the equator. We’ve been challenged by issues with antenna aiming, working at microwave frequencies and rain, but K2QA and I finally achieved some success yesterday in copying high-res images from GOES-16. Checking the files shows about 700 more pictures downloaded from the satellite over the last 2 days.
GOES satellites transmit beautiful high-res shots of the entire earth, which we’re hoping to receive by leaving the decoder running (it runs on a Raspberry Pi), so hopefully by Tech Saturday we can show some more stunning images, but given that this satellite is further away than anything on Earth can possibly be, we are claiming the GCARC SWL DX record with these pix! More information is at the W2MMD Satellite Blog, if you’re interested in this project.
W2MMD Satellite Station - August 17, 2018
By Jon Pearce, WB2MNF
If you've ventured into the VHF Room at the Clubhouse you may have noticed some changes in the satellite station. You may even have been surprised, as WB2ZBN was earlier this week, to see the satellite antennas moving when nobody was operating that station. We've made some progress on a few interesting projects in the last couple of weeks.
Our first project was creating communication with the FalconSat3 satellite. Built and launched by the US Air Force Academy in 2005, it reached the end of its military service earlier this year and was turned over to ham use. This satellite uses a 9600 baud data feed to provide an orbiting BBS station as well as real-time APRS digipeating. It's in a low inclination orbit which means that there are never any overhead passes and we needed to beef up the receive capability on 70 cm to receive. Adding a mast-mounted preamp installed by KB2AYU helped a lot to bring the signal up to a reliable level, and figuring out the proper receive settings on the SDR radio (wide-band FM, not narrow-band which trims off some frequencies needed for 9600 baud) were important. The final challenge was getting the transmit audio levels right from the sound modem software in the computer to the RigBlaster connected to the Yaesu 847. K2ZA and I did some experimenting using a separate SDR radio and a FT-1D HT that receives 9600 baud APRS signals to finally get the audio levels set to where the satellite would decode them. And because the FalconSat passes were early in the AM we left the station running with the antenna rotation and Doppler shift managed by the computer and would check each day to see whether we had successfully uploaded and downloaded files and messages. Finally this week we saw a message from another station confirming that they had read the message that we had uploaded. That confirmed that the whole system was functional, and although there's probably a little more work do to I think the major FalconSat project goals have been achieved.
Our second success was getting remote access to the SDR radio and antenna rotation. Fortunately the SDR Console software has a server component that will let another copy of SDR Console on the same network connect to one of the radios on the server. The IQ packets from the server radio transfer to the remote client software, letting that operator operate almost identically to how it would work at the W2MMD computer console. That's half of the battle - the other half was getting the antennas to rotate based on remote commands. Fortunately the PST Rotator software also has a server component that can be controlled by a remote client on the same network. The remote client can command the az-el rotation of the server at W2MMD to follow the desired satellite. The combination of these capabilities allows the remote operator to receive satellite signals as if he was sitting in the W2MMD shack. I tried that successfully from home earlier this week listening for one of the BIRDS-2 satellites that were launched last week from the ISS and was able to hear the CW telemetry from one of those satellites. But those two ISS passes were around noontime on Tuesday, and WB2ZBN was working alone outside at the Clubhouse and suddenly saw the satellite antennas rotate. So if you're hanging around the Clubhouse and see antennas moving, it's because of this functionality. (The network connection is through a VPN set up by K2QA.)
The final project, which is largely complete, is an automatic antenna switcher that will switch the 2 meter and 70 cm antennas between the SDR radio and the Yaesu 847. This is necessary because some satellites use a 2 meter uplink and a 70 cm downlink, while others use the opposite configuration. Previously we switched them manually, but I frequently forgot to make the switch (even after adding a warning note on the monitor) and often missed part of a pass because the proper antenna wasn't connected. Because the tracking software sets the radio frequencies, I figured that we could sniff the CAT commands going to the Yaesu and build up some Arduino code for an automatic switcher. After adding some relays, an Arduino Mega and relay board and a lot of trial and error, this capability now works. In the PST Rotator software the operator can switch from FalconSat3 (70 cm down, 2 meters up) to Funcube 1 (opposite configuration) with the frequencies on both radios changing and the antenna relays clicking to the new position. It's pretty cool to watch! But while my programming skills are OK, my building skills are mediocre at best, so perhaps someone with better skill will take the black box with wires hanging out of it and build a more elegant enclosure for it.
Our next project is to attempt to decode telemetry from the Longjiang satellite that's orbiting the moon. It's on 70 cm and uses the JT-4 encoding scheme that's used for moonbounce. Several other ham stations have done this successfully - I'm hoping that we can hear it but am concerned that we may need to upgrade the 70 cm antenna. That's a project for the fall.
There's plenty of opportunity for others to get involved in the satellite station. It works great for SSB QSOs with the CAS and XW satellites, which are currently overhead in the early evening hours. If you'd like to work the station, get K2ZA or me to check you out on its operation and then give it a try, and check out the blog at: http://w2mmdsatellite.blogspot.com or on the Club's website page "W2MMD Satellite Blog", where we chronicle our activities. Satellite operating is very different from terrestrial hamming, and the changes and challenges make this form of ham radio a lot of fun.
By Jon Pearce, WB2MNF
If you've ventured into the VHF Room at the Clubhouse you may have noticed some changes in the satellite station. You may even have been surprised, as WB2ZBN was earlier this week, to see the satellite antennas moving when nobody was operating that station. We've made some progress on a few interesting projects in the last couple of weeks.
Our first project was creating communication with the FalconSat3 satellite. Built and launched by the US Air Force Academy in 2005, it reached the end of its military service earlier this year and was turned over to ham use. This satellite uses a 9600 baud data feed to provide an orbiting BBS station as well as real-time APRS digipeating. It's in a low inclination orbit which means that there are never any overhead passes and we needed to beef up the receive capability on 70 cm to receive. Adding a mast-mounted preamp installed by KB2AYU helped a lot to bring the signal up to a reliable level, and figuring out the proper receive settings on the SDR radio (wide-band FM, not narrow-band which trims off some frequencies needed for 9600 baud) were important. The final challenge was getting the transmit audio levels right from the sound modem software in the computer to the RigBlaster connected to the Yaesu 847. K2ZA and I did some experimenting using a separate SDR radio and a FT-1D HT that receives 9600 baud APRS signals to finally get the audio levels set to where the satellite would decode them. And because the FalconSat passes were early in the AM we left the station running with the antenna rotation and Doppler shift managed by the computer and would check each day to see whether we had successfully uploaded and downloaded files and messages. Finally this week we saw a message from another station confirming that they had read the message that we had uploaded. That confirmed that the whole system was functional, and although there's probably a little more work do to I think the major FalconSat project goals have been achieved.
Our second success was getting remote access to the SDR radio and antenna rotation. Fortunately the SDR Console software has a server component that will let another copy of SDR Console on the same network connect to one of the radios on the server. The IQ packets from the server radio transfer to the remote client software, letting that operator operate almost identically to how it would work at the W2MMD computer console. That's half of the battle - the other half was getting the antennas to rotate based on remote commands. Fortunately the PST Rotator software also has a server component that can be controlled by a remote client on the same network. The remote client can command the az-el rotation of the server at W2MMD to follow the desired satellite. The combination of these capabilities allows the remote operator to receive satellite signals as if he was sitting in the W2MMD shack. I tried that successfully from home earlier this week listening for one of the BIRDS-2 satellites that were launched last week from the ISS and was able to hear the CW telemetry from one of those satellites. But those two ISS passes were around noontime on Tuesday, and WB2ZBN was working alone outside at the Clubhouse and suddenly saw the satellite antennas rotate. So if you're hanging around the Clubhouse and see antennas moving, it's because of this functionality. (The network connection is through a VPN set up by K2QA.)
The final project, which is largely complete, is an automatic antenna switcher that will switch the 2 meter and 70 cm antennas between the SDR radio and the Yaesu 847. This is necessary because some satellites use a 2 meter uplink and a 70 cm downlink, while others use the opposite configuration. Previously we switched them manually, but I frequently forgot to make the switch (even after adding a warning note on the monitor) and often missed part of a pass because the proper antenna wasn't connected. Because the tracking software sets the radio frequencies, I figured that we could sniff the CAT commands going to the Yaesu and build up some Arduino code for an automatic switcher. After adding some relays, an Arduino Mega and relay board and a lot of trial and error, this capability now works. In the PST Rotator software the operator can switch from FalconSat3 (70 cm down, 2 meters up) to Funcube 1 (opposite configuration) with the frequencies on both radios changing and the antenna relays clicking to the new position. It's pretty cool to watch! But while my programming skills are OK, my building skills are mediocre at best, so perhaps someone with better skill will take the black box with wires hanging out of it and build a more elegant enclosure for it.
Our next project is to attempt to decode telemetry from the Longjiang satellite that's orbiting the moon. It's on 70 cm and uses the JT-4 encoding scheme that's used for moonbounce. Several other ham stations have done this successfully - I'm hoping that we can hear it but am concerned that we may need to upgrade the 70 cm antenna. That's a project for the fall.
There's plenty of opportunity for others to get involved in the satellite station. It works great for SSB QSOs with the CAS and XW satellites, which are currently overhead in the early evening hours. If you'd like to work the station, get K2ZA or me to check you out on its operation and then give it a try, and check out the blog at: http://w2mmdsatellite.blogspot.com or on the Club's website page "W2MMD Satellite Blog", where we chronicle our activities. Satellite operating is very different from terrestrial hamming, and the changes and challenges make this form of ham radio a lot of fun.
April 14, 2018
ISS SSTV images from W2MMD Satellite Station
Over the past few days the Russian crew on the ISS has been broadcasting SSTV images throughout the orbits. I set up the new software-defined radio setup at the W2MMD clubhouse to track and record those images since Thursday, and caught two passes there today. I pulled out the best downloads of each image which you can see below. I also took a short video of one of the passes – you can see the SSTV signal on the SDR waterfall as the image materializes on the MMTV screen. It’s all pretty cool – hope it’s interesting to a few people.
Here is the link to the Club's YouTube Channel where you can find Jon's video:
https://www.youtube.com/channel/UCHi3sAuEY374AIstXNANUOw
That station is largely operational, and it gets full-strength signals from horizon to horizon. We’ve had many SSB QSOs on the XW satellites and copied APRS packets from the APRS satellites as well as telemetry from the Fox and Funcube satellites. We’ve also downloaded weatherfax images from the NOAA satellites. We’re now working on getting 9600 bps telemetry decoded from Falconsat3, and once that’s working we want to get a 9600 bps uplink going as well. It would also be cool to get the 10 meter PSK uplink working although that would require an additional antenna.
Currently the best passes for the analog satellites are in the early evening (5-7 PM), and for the digital satellites are in the late morning. I’m going to try to be over there some evenings this week (except for Wednesday) and hopefully next Saturday AM. If anyone else is interested in working satellites let me know and we’ll arrange a time to be there together.
73 de Jon WB2MNF
Jon <at> pearcefamily <dot> org
ISS SSTV images from W2MMD Satellite Station
Over the past few days the Russian crew on the ISS has been broadcasting SSTV images throughout the orbits. I set up the new software-defined radio setup at the W2MMD clubhouse to track and record those images since Thursday, and caught two passes there today. I pulled out the best downloads of each image which you can see below. I also took a short video of one of the passes – you can see the SSTV signal on the SDR waterfall as the image materializes on the MMTV screen. It’s all pretty cool – hope it’s interesting to a few people.
Here is the link to the Club's YouTube Channel where you can find Jon's video:
https://www.youtube.com/channel/UCHi3sAuEY374AIstXNANUOw
That station is largely operational, and it gets full-strength signals from horizon to horizon. We’ve had many SSB QSOs on the XW satellites and copied APRS packets from the APRS satellites as well as telemetry from the Fox and Funcube satellites. We’ve also downloaded weatherfax images from the NOAA satellites. We’re now working on getting 9600 bps telemetry decoded from Falconsat3, and once that’s working we want to get a 9600 bps uplink going as well. It would also be cool to get the 10 meter PSK uplink working although that would require an additional antenna.
Currently the best passes for the analog satellites are in the early evening (5-7 PM), and for the digital satellites are in the late morning. I’m going to try to be over there some evenings this week (except for Wednesday) and hopefully next Saturday AM. If anyone else is interested in working satellites let me know and we’ll arrange a time to be there together.
73 de Jon WB2MNF
Jon <at> pearcefamily <dot> org