ad: elecraft

SDRplay as satellite downlink receiver?

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

ad: L-HROutlet
ad: l-rl
ad: abrind-2
ad: L-MFJ
ad: Left-3
ad: L-Geochron
ad: Left-2
  1. W5SAT

    W5SAT Ham Member QRZ Page

    You can record "RF" - the full bandwidth that your SDR is set to or "IF" - just what the output bandwidth is set to. or you can actually record both at once. This is a really nice feature of HDSDR.
  2. WD9EWK

    WD9EWK Ham Member QRZ Page

    OK, I had never tried the IF recording option. I'll have to take a closer look at that when using the SDRplay, and get it so I can see most or all of the transponder, without having to record anything outside of the transponder. I'd expect I need to set the output bandwidth in HDSDR higher than the 12000 I use for SSB or something between 16000 and 20000 for FM. More to try...
    Last edited: Sep 4, 2015
  3. WD9EWK

    WD9EWK Ham Member QRZ Page


    I just worked another AO-73 pass, maximum elevation 13 degrees to my east. I had no problems copying the transponder and 145.935 MHz telemetry until the satellite went below the hills/mountains to my north. Other than seeing a CW signal above my spot on the transponder, I didn't hear anyone else.

    If I don't fall asleep at the keyboard, I will try the next AO-73 pass (10pm PDT Saturday/0500 UTC Sunday), and possibly even a 50-degree SO-50 pass around 11.35pm PDT/0635 UTC. Weather is not as hot as it has been in the evenings here, and this is a holiday weekend, so I'll take advantage of this.

  4. WD9EWK

    WD9EWK Ham Member QRZ Page

    Hi again!

    The 0500 UTC AO-73 pass with my FT-817ND/SDRplay combination was another success! It was a 49-degree pass, and I worked two stations - Tom WA0POD in southern California, and Hector W5CBF who is currently in Louisiana. Working with an SDR receiver is fun, since I can use the screen along with my ear to know when to twist my antenna. The RF recording is still on my 8-inch tablet, and I may post it in my Dropbox space later tonight or sometime tomorrow.

    I still want to try SO-50 with the SDRplay, but with a different transmit radio. I will use an HT with a hand mic for the 145.850 MHz transmitter, and the SDRplay with HDSDR for the receiver. I want to see if there is any difference when using a different radio when working SO-50 with the SDRplay. I will try the upcoming SO-50 pass in the next hour, since that will be a nice high pass where I can clearly see the tablet's screen in the dark back yard.

  5. WD9EWK

    WD9EWK Ham Member QRZ Page


    A late update... I just worked the SO-50 pass just after 0635 UTC. Nice, high pass, and a chat of several minutes with the only other station on there (Tom WA0POD, in southern California). Unlike my Saturday morning attempt on another SO-50 pass using an FT-817ND as my transmitter, I had no problems hearing myself on the SDRplay/HDSDR receive combination when transmitting from my Wouxun KG-UV9D 2m/70cm HT at 5 watts. I observed a couple of fades on the downlink, but had no problems hearing myself when transmitting, and no problems hearing Tom until he signed off. After he left, I didn't hear anyone else on the satellite before my LOS.

    Here are a couple of photos from tonight's setup I used to work SO-50. First, the wider-angle photo showing my station including Elk antenna:


    And a close-up of the KG-UV9D HT, 8-inch tablet with HDSDR, and SDRplay to the right of the tablet:


    I still use the Belkin Rockstar audio splitter off the tablet's headphone jack, so I can make an audio recording separate from the tablet and HDSDR, along with the earbuds so I can hear the downlink without any audio feedback into the HT's speaker/mic. The mouse is in the center, as it was my tuning "knob" - something I didn't have to use much, with HDSDR's AFC function tracking the Doppler effect on the SO-50 downlink pretty well. I only had to manually adjust the receive frequency a couple of times during the pass. The flashlight helps see my workspace on the top of the trash can, as it was after 11.30pm local time for this pass. My MFJ 2m/70cm diplexer is out of sight, behind the tablet.

    I will upload the HDSDR RF recordings to my Dropbox space during the day Sunday. I will have to remove other recordings to make room for tonight's recordings.

    With tonight's success with SO-50, I'm hoping I won't run into issues when using the SDRplay as the receiver for FO-29. I will try that, either on Sunday or Monday afternoon. I may also try AO-7, depending on how well other stations are behaving during those afternoon passes. Then I can write a lot more about using this particular SDR receiver, and also how the software has been behaving on a Windows 10 tablet (so far, so good).

    Last edited: Sep 6, 2015
    W5SAT likes this.
  6. W5SAT

    W5SAT Ham Member QRZ Page

    Thanks for the reports, Partick. Nice to hear about how well this is working out. I just caught part of the AO-73 pass a couple hours ago and heard your 2 QSOs with Tom and Hector. I tried to setup my recording but it didn't com out right so... nevermind that. Let us know when you post the recordings to your dropbox - I'd like to check them out.
  7. WD9EWK

    WD9EWK Ham Member QRZ Page

    I am going to deal with uploading the RF recordings during the day. I want to get some sleep, since I know I won't sleep all day. I'm wanting to try FO-29 and AO-7 tomorrow or Monday, so I can say I have tried all of the voice-capable satellites with the SDRplay. I am still stumped as to why I was desensing myself when transmitting to SO-50 from an FT-817ND this morning, but at least I know a workaround - use something else as the transmitter when working SO-50 with the SDRplay as my downlink receiver.

  8. WD9EWK

    WD9EWK Ham Member QRZ Page


    After almost an hour for the uploading, I now have the two HDSDR RF recordings from last night's AO-73 and SO-50 passes I worked in my Dropbox space:

    Look for the file name starting with HDSDR_20150906_050004 for the AO-73 pass, and the file name starting with HDSDR_20150906_063900 for the SO-50 pass. I had to pull most of my other HDSDR RF recordings off the Dropbox space to make room for these recordings.

    I had set the Gain Reduction to 0 dB for these passes, and that didn't seem to cause any problems. Other than that and the different LO frequency I used for the SO-50 RF recording, I used the same settings that I had in the screenshots earlier in this thread.

    I was asked on Twitter earlier this morning if I would recommend the SDRplay over the FUNcube Dongle Pro+. At this point, for working AO-73 and SO-50, it's basically a draw. Both receivers do well, as long as I am not desensing the receiver in any way. In terms of how I use these receivers with HDSDR, I would have liked to see IF bandwidths in the SDRplay smaller than 200 kHz like I have with the FUNcube dongle. Most times, I don't need 200 kHz when working satellites, and smaller bandwidths lead to smaller RF recordings. Other than that small nit, the two receivers are good. Both are nice products from across the pond in the UK, and both work with my Windows tablets. I still need to try the SDRplay on FO-29 and AO-7, before I may be able to make a clear recommendation of one receiver over the other.

    Even though the SDRplay costs less than the FUNcube Dongle Pro+, I still like the dongle and the fact that its sales support the FUNcube project. The SDRplay's wider frequency range, options for larger bandwidths, and lower cost make a good case for it being a satellite downlink receiver. This is still a work-in-progress, and I'll continue to add to this thread as I use the SDRplay.
  9. W5SAT

    W5SAT Ham Member QRZ Page

    Patrick, I downloaded both of your files - for AO-73 and SO-50. Regretting not jumping on that SO-50 pass - just you and Tom on there...

    Anyway, I guess you haven't tried recording IF only on HDSDR - make those big uploads go quicker with 1/10th file size.

    Strange you were having troubles with the FT-817 but the Wouxun worked OK on SO-50. I can see the noise floor jump up maybe 2 dB when you transmit on the recent recording (Wouxun). Be interested to see what happens with the 817 transmitting - noise floor or look at a wide bandwidth for any spurious emissions.
  10. WD9EWK

    WD9EWK Ham Member QRZ Page

    I have seen similar issues before, and have dealt with it by separating radios a little more. I'm now keeping my tablet in between the FT-817ND and SDRplay. It worked on the last FO-29 pass, where I could hear myself in CW and SSB during the pass. I didn't make any QSOs, and there was just a little too much daylight to clearly see the tablet's screen in the yard.

    I'll have to go over the schematics and block diagrams on the SDRplay to better understand its bandpass filtering. I know the FUNcube Dongle Pro+ uses SAW filters at 2m and 70cm, but it doesn't have filters for other parts of what it can hear.


Share This Page