SDRplay as satellite downlink receiver?

Discussion in 'Satellite and Space Communications' started by WD9EWK, Aug 24, 2015.

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  1. WD9EWK

    WD9EWK Ham Member QRZ Page

    The AFC feature in HDSDR helps keep the SSTV signal lined up in whatever program you use to decode the pictures. Some SSTV programs/apps, like the RX-SSTV program I use on my Windows PCs, have their own AFC function to help it track the signal. I use AFC in both places when I decode SSTV pictures.

    Even though many amateur transceivers and receivers can receive ISS SSTV pictures on 145.800 MHz without any frequency adjustments, you can clearly see the small amount of Doppler on the received SSTV signals when using an SDR receiver. Here are screenshots taken at different points in the reception of an SSTV image. Here's one screenshot at approximately 1 minute into the transmission, showing both HDSDR and RX-SSTV on the screen:


    The zig-zag at the top of the HDSDR waterfall was due to moving the waterfall so I could see all of the received signal on my screen. I wanted to have the relevant parts of each program's window visible in the screenshots.

    At 2 minutes into the transmission...


    This was the view, just after the 3-minute transmission concluded:


    Note the TUNE frequency showing in the HDSDR window of each screenshot. The frequency was around 145.802 MHz when the 3-minute transmission started, and I pressed the AFC button in HDSDR as soon as I started to see and hear the transmission. You can also see the HDSDR waterfall in each screenshot, where the received signal was showing up at an angle - another indication that the Doppler effect was at work. I had RX-SSTV connected to HDSDR through a virtual audio cable, and you can see how much of the picture I received at each point in the transmission when I made these screenshots.

    From that transmission on Wednesday (13 April) afternoon came this picture:


    I posted my HDSDR RF recording (big WAV file), a smaller MP3 file with the received audio, these pictures/screenshots, and other pictures/screenshots in my Dropbox space at (look for the folder "20160413-ISS_SSTV-DM43").

    Great to hear!

  2. KA2CZU

    KA2CZU XML Subscriber QRZ Page

    btw I did notice some packet signals in the waterfall up on 145.825... not sure if they'll show up in the recording (which I honestly haven't even checked to see if it "worked"... I simply pressed record start/stop during the pass)
  3. WD9EWK

    WD9EWK Ham Member QRZ Page

    The 145.825 MHz packet/APRS digipeater remained operational during the SSTV activity.

    If the packet signals fell in the bandwidth you were receiving, they would have also gone into the RF recording made by HDSDR. You could pipe the audio from the 145.825 MHz traffic into another program to decode packet/APRS signals - or use an old-school audio patch cable from the speaker jack on your computer, and send the audio into a TNC - to see what was coming down on that frequency.

    When I was trying to decode SSTV, I made the zoom on the HDSDR waterfall so that I could just focus on the 145.800 MHz (+/-) signal. I also recorded 145.825 MHz traffic in my RF recordings. I'm not worrying about going back to decode the packet signals, but I could see them start to show up in real time on the right edge of the waterfall when I was outside with my portable station.

    KA2CZU likes this.
  4. WD9EWK

    WD9EWK Ham Member QRZ Page


    Once again, I used the SDRplay as the downlink receiver for working AO-85 on Sunday (22 May) afternoon. This time, as I have done a few times before, I used a separate station to work stations on the satellite while the SDRplay recorded the downlink on my tablet with HDSDR. I was able to work 3 stations in southern California and Arizona while recording the downlink and uploading 37 data frames from that pass.

    Rather than posting a duplicate of what I did in the other thread about the KG-UV9D, here's the link to see that post in the other thread:

  5. WD9EWK

    WD9EWK Ham Member QRZ Page


    Earlier this morning, I took advantage of being home on a weekday where AO-73's transponder was turned off, so I could try copying telemetry using my SDRplay receiver and the AMSAT-UK VHF crossed dipole. I have had good luck using that antenna with my FUNcube Dongle Pro+ in the past, and wanted to see how well I could do today.

    The first AO-73 pass I had this morning started at 1627 UTC, going to a maximum elevation of almost 45 degres to my east.


    I set up my station on a trash bin against the east wall of the yard, for a little bit of shade on the top of the bin:


    I had the AMSAT-UK VHF crossed dipole on an 8-foot mast and tripod I originally bought many years ago for a Buddipole portable dipole, using a Diamond mast mounting kit to hold the antenna to the mast. On top of the trash bin, my station - SDRplay SDR receiver, 8-inch Windows 10 tablet with HDSDR, and a Bluetooth mouse.


    Once the pass started, it didn't take long to have a signal sufficient for the FUNcube Dashboard software to decode, but I wasn't decoding the telemetry in real time. I made an RF recording with HDSDR, so I could decode the telemetry later, but could tell from the waterfall in HDSDR the strength of the signal. Here is an example of the HDSDR screen around the midpoint of the pass, showing how strong the AO-73 telemetry downlink was at that time:


    After the pass, I took the RF recording from HDSDR - a large WAV file, almost 600 MB in size, and ran that through a virtual audio cable into the FUNcube Dashboard software. When the playback finished, I had decoded 103 frames of telemetry:



    During a 75-degree pass in September 2015 over the Labor Day holiday weekend, I decoded 113 frames using the same tablet with a FUNcube Dongle Pro+. I think I could have done as well this morning with the SDRplay, if I had a pass with a higher maximum elevation like that pass last year. Still, successfully decoding over 100 frames in one AO-73 pass using a station with an omnidirectional antenna - and doing this with a portable station - is nice.

  6. WD9EWK

    WD9EWK Ham Member QRZ Page


    An update... during the ARRL Field Day on 25-26 June, I used my SDRplay for the downlink receiver when working XW-2F on a western pass Saturday evening of that weekend. By the time the pass came by, I wasn't dealing with a lot of sunlight. As usual, I could clearly see the activity on the transponder, as well as the two telemetry downlinks (CW, high-speed data). From my Field Day location west of Flagstaff AZ, I worked K6FW on that pass, then tried unsuccessfully to make additional QSOs. I could see and hear the activity on there, and I have an RF recording from that pass.

    I did not use the SDRplay and tablet for an early FO-29 pass, as it was too bright to see the tablet's screen - and the tablet may have overheated if I went with it at that time of the early afternoon. I did not work AO-85, so I didn't have any chance to use it to work the transponder while collecting the telemetry.

    I haven't posted the RF recording from HDSDR for this pass to my Dropbox space yet, but will on request. I have a lot of those recordings from XW-2F and other satellites up there already.

  7. WD9EWK

    WD9EWK Ham Member QRZ Page


    Last night (Monday, 1 August), I tried an AO-85 pass that covered the central and western parts of the continental USA. The pass went up to a maximum elevation of almost 69 degrees:


    For this pass, I went out to the end of my driveway, and set up my station on a small table. My transmitter was an Icom IC-2730A 2m/70cm FM mobile, and I had my SDRplay receiver connected to an 8-inch Windows 10 tablet that ran HDSDR. The IC-2730A and SDRplay were connected through a diplexer to an Elk handheld 2m/70cm log periodic. Here are a couple of pictures of this setup:


    And a closeup of the gear on the table:


    The wheel on the Bluetooth mouse near the tablet is used like a VFO knob in HDSDR. The mouse also helps with using HDSDR generally, as most ham radio programs in Windows were not designed for use with touch screens.

    I could have decoded the telemetry in real time while I was working stations, but I normally make an RF recording in HDSDR and play that later to decode telemetry. As I was recording the pass including the telemetry, I worked 4 stations in Arizona, California, and Oklahoma. I also heard another California station on there, someone I didn't work.

    After the pass, as I typically do when I work AO-85 or AO-73 with my SDR receive setup, I decoded the telemetry. I used HDSDR to play the recording through a virtual audio cable into the FoxTelem software. HDSDR uses AFC to track the frequency during the playback, and FoxTelem is decoding the telemetry that came down with the voice traffic.


    When the playback finished, I had decoded 90 telemetry frames from that pass. Not bad, for using a portable setup. Here's a screenshot from one tab in the FoxTelem program, after the playback finished:


    This was an example of a good pass, both for making contacts and for the telemetry. Working at home with my portable setup is my way of remaining active on the air, despite living in an area with antenna restrictions. And this is still fun...

    W5PFG likes this.
  8. WD9EWK

    WD9EWK Ham Member QRZ Page


    On Sunday, 4 September 2016, I took a short drive north of Phoenix to the Tuzigoot National Monument. I made it to the monument in time for an AO-73 pass, and was able to see my tablet's screen well enough to use it and my SDRplay to work an AO-73 pass. Fun!

    The pass was almost directly overhead, slightly to my west. An easy pass to work from this site, in the Verde Valley near Clarkdale, Arizona:


    I set up my usual gear for an SSB satellite pass - FT-817ND transmitter, SDRplay with 8-inch Windows 10 tablet and HDSDR for my receiver, and Elk 2m/70cm log periodic antenna through a diplexer:



    At the midpoint of the pass, around 1654 UTC, AO-73's footprint covered much of the continental USA. Not the entire country, but certainly anyone west of the Mississippi River was covered:


    With HDSDR, I was able to keep an eye on the 145.935 MHz (+/-) telemetry downlink as well as the transponder. Here's the view at 1650 UTC, early in the pass:


    See the CW streaks in the transponder, probably stations trying to find themselves.

    About 3 minutes later, just before the midpoint of the pass, it looked like this:


    A couple of minutes after this, just as the satellite started descending toward the horizon:


    A CW streak going down and then back up the transponder.

    I worked 3 stations during this pass - Clayton W5PFG and Glenn AA5PK in Texas, along with Frank K6FW in California. I heard one or two others trying to call me, but they were always just off my downlink enough I could not get their call signs before the transmissions ended. These were the first 3 QSOs I made as part of my activation of Tuzigoot for National Parks on the Air, the 8th different National Park Service site I have activated during 2016 - and all via satellite. I also worked AO-85, FO-29, and the ISS from Tuzigoot.

    The SDRplay, after a year or so of using it, still does a great job with amateur satellite downlinks. The SDRuno software now available from SDRplay is also good, but on my Windows 10 tablets I still prefer HDSDR for its low overhead and ease of use (a single window, which can occupy the full tablet screen).

    KD6RF likes this.
  9. KF7R

    KF7R Ham Member QRZ Page

    Encouraged by Patrick's experiments with a SDRPlay as a linear satellite receiver, I bought one back in May and I've been doing some experimentation on my own.

    I currently work all linear sats with a FT-817 as the uplink transmitter, an Arrow or Elk antenna and a Toshiba laptop running SDRuno. Both the 817 and SDRPlay are controlled by SatPC32, making it easier to move around the waterfall and finding my signal, and staying on frequency.

    With this setup, I operated away from home two days ago and was able to complete a SSB contact over AO-7 with AL7RS in Nome, Alaska, close to the Bering Strait. Today, I decided to hook up my straight key to the radio and worked Dan again over CW, first time on that mode after more than 20 years. And, with the SDRPlay/FT-817 I was able to work CY9C in St. Paul Island, Canada on a 3ยบ FO-29 pass.

    For a simple and frugal station, the SDRPlay works wonderful. Being able to look at the signals on the computer screen is a big plus!
    W5SAT, KD6RF and WD9EWK like this.
  10. WD9EWK

    WD9EWK Ham Member QRZ Page

    I'm happy the SDRplay is working well for you. Thanks for posting your comments here!

    The need to use a computer with the SDRplay may violate the KISS principle compared to using another FT-817 or other "real" radio. Most hams have the computer, or can get a laptop or tablet for not too much. The SDRplay is US$ 149, so it with a laptop or tablet could come in much less than the price on another FT-817 - helping to remove one obstacle for some (many?) to try working SSB and CW via satellite.

    For my own SSB/CW satellite operating, I travel with two FT-817NDs along with the SDRplay and an 8-inch tablet. If it's not too bright or not too hot outside, I'll use the SDRplay and tablet. Otherwise, the two FT-817NDs are used. Either way, I have a nice system that lets me work the SSB/CW satellites, and could also be used for FM birds too.


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