Receiving SSTV from ISS
July 2025
Finally. ISS is transmitting SSTV again at 145.8MHz.
Went and rebuilt the extremely simple V-dipole. Simply cut 2 single core copper wires to around 50cm in length. Solder it to a coax cable and terminate it at a SMA male(NOT RPSMA male!!!) connector. Screw the other end into the RTL SDR or whatever SDR you have. Here is my setup:
Make sure to add strain relief to the wires and transmission line or else they will break since its solid core. I used zip ties to secure them in place. Next, I compiled QSSTV from source.
mkdir src/buildqmake ..makecp qsstv /usr/local/bin
Done, as simple as that. Fired up GQRX and send the output using pavucontrol into the program. Make sure to create a dummy audio sink if you don’t want to hear the output. You can also use the audio monitor as input and feed that into the program. Using the Look4Sat android application, available on F-Droid, the next pass is coming around 9pm. Lets get everything setup outside, so we don’t miss it. Now the transmissions happen every 2 minutes. So dont be surprised if we don’t hear anything at first. This is different from NOAA and METEOR satellites, which are always transmitting.
The decoded images are saved in ~/qsstv/rx_sstv by default. Change if needed. One thing I hate about my QTH is the lack of a clear LOS to the satellite near the horizon. This particular pass will be conming from West -> East. So I setup in my backyard where I have an ok LOS. Not as good as an open field, but the best I can do for now. Of course my dream is to go onto the roof, but I don’t trust myself and its not easy going up there. Pretty dangerous too.
Day 1 25-07-14:
Start decoding at elevation: 19.4 above horizon
We got the end of transmission, now we wait 2 minutes. DAMMIT!!!
Correction… You don’t need to wait 2 minutes, its around 30 seconds.
Set the bandwidth to about 18k. Wasn’t much doppler effect at VHF frequencies, but adjusted the center frequency slightly above when < peak AOH and frequency slightly below after passing maximum AOH.
75 above horizon, started another transmission. Got it at the perfect time!!! This is what QSSTV output:
The top got cut off. Thankfully I have a .wav audio recording. Lets play it back and see if we can redecode it and get the full picture. Damn that is perfect. Absolutely beautiful. This is why having a audio recording alongside is very important. As soon as ISS hits 0 degrees above horizon, I start a wav recording in GQRX. Will continue doing so for the rest of the transmissions.
Day 2 25-07-15:
2nd day. All setup and ready to go. Lets document my experience here:
Nice got a perfect decode again. In my location I get a approach blindspot. I don’t receive anything until about 25 AOH. Then there is a minor blindspot at around 70 AOH. Then the AFT AOH is very good, I get very strong signal at 25 AOH. At this point, the ISS is usually done the transmission. Here is what I captured:
Very nice.
Day 3 25-07-16:
All setup and ready to go. Lower pass today at 60 AOH. Lets see what we get.
This pass wasn’t the best. ISS started transmitting at 40 AOH, finished previous transmission around max AOH at 60. I had to redecode through the audio recording because too much noise. Playback decode was successful.
Whats very interesting is my signal near the horizon is actually better than directly above. I got max SNR at 20 AOH. Anything below 10 is when the signal tapers off. Seems like my v dipoles are very good at catching signals near the horizon. Decode wasn’t perfect, you can see lots of noise in signal. Still can make out image and text, which is what matters. Very good.
Day 4 25-07-17:
Not very good today. Started transmitting at peak AOH of 60 degrees. This is a null for my antenna. So I didn’t get the first part of the transmission. This is what I got:
Day 5 25-07-18:
Good pass today. Peak AOH of 80. Got a new 50 ohm coax, shorter, so less attenuation. Lets see how we do, should get a perfect decode I hope. Might do 2 passes today. Second pass at 11pm has peak AOH of 75, still very good.
Nice not perfect, null at peak AOH. Still much better than yesterday, didn’t need to use the audio to redecode.
Nice second decode, not as good. Huge null spot as the ISS was passing 30 AOH. This pass was from North-west to South-east. A bad spot for me. Still got most of the data, which is what matters. Will try rotating antennas 90 degrees for North->east passes. See if it can reduce null spots.
Day 5 25-07-19:
Hopefully catch 2 passes today. This is what I decoded:
Sad same image I received on the 2nd day. The second pass is later at 10pm, so will try to catch that one.
Man I think my luck is running out. Only started capturing at 20 AOH. Not very good. I think I should continue using 50 ohm coax, something happened with my other antenna. The antenna using 75 ohm TV coax is either not performing very well, or something else is happening.
Event ends tomorrow, won’t be able to capture anything because all the passes come later in the day in my region. It was fun while it lasted!!