Hi!

I received an e-mail asking about a demonstration of satellite operating, possibly this afternoon if I had the time. It is still warm here in the Phoenix area, but not over 100F/38C today, so I went to a city park in the southeast corner of Phoenix in grid DM43ah. I was out here a couple of months ago, and this time the plan was to try focusing on the satellites from AMSAT and China that had been recently launched. I worked SO-50, FO-29, the ISS, XW-2E, and AO-85 from the park. While working AO-85, XW-2F was passing by at the same time. I was able to hear both of these satellites, as I focused on working AO-85.

The demonstration started in the mid-afternoon, with an SO-50 pass just after 2pm/2100 UTC. I did a simple demonstration, using my Kenwood TH-D72A HT and Elk log periodic, working a few stations. Around 2140 UTC, there was a very nice FO-29 pass, and I worked it using one of my FT-817NDs and the Elk log periodic. This was only the second time I tried working FO-29 half-duplex, and I was able to chat with Tom WA0POD for a couple of minutes for my only QSO on that satellite.

The ISS passed by around 2200 UTC, and I was unsuccessful in sending my packets through the digipeater. When I got home tonight, I think I figured out the issue - wrong packet path on 145.825 MHz. Oops. We heard a bit of activity from around the western USA, including KG7NXH (not far to the east of this park, in another Phoenix-area suburb). Then a break for lunch, and talking about the new satellites and other topics like using SDR receivers, before the fun really started...

For passes of XW-2E, XW-2F, and AO-85 around 0100 UTC, I went back to that city park and set up a couple of stations. One I used for my operating:

Yaesu FT-817ND for SSB transmit Icom IC-2820H for FM transmit SDRplay SDR receiver 8-inch HP Windows 10 tablet with HDSDR (making RF recordings of the passes) Elk 2m/70cm log periodic antenna

and another station for receiving:

FUNcube Dongle Pro+ 10-inch Winbook Windows 10 tablet with HDSDR AMSAT-UK (Winkler) VHF crossed dipole

XW-2E came first. I heard a couple of stations on, tried to get a clear spot to call CQ, and ended up making 4 QSOs while keeping an eye on the clock. I saw that XW-2F and AO-85 were passing by our location around the same time. I had worked XW-2E in SSB, so I suggested I try AO-85 in FM. This was an interesting experience...

For the first few minutes of the pass, I saw - and occasionally heard - the XW-2F CW beacon that was just below the AO-85 FM/data downlink. I was using narrow FM, about 14 kHz in HDSDR, and I raised the audio filter for the low side of the audio passband to eliminate any part of the slow-speed data from reaching my ears. Did I mention I am really enjoying SDR for my satellite work? :-) This is something that made the audio more pleasing to hear. Not stereo quality, of course, but no buzzing from remnants of the telemetry making it into the audio we hear on our radios when working the FM repeater.

About 10 kHz or so above the AO-85 downlink, I saw an SSB signal pop up in the XW-2F transponder. When I played the HDSDR RF recording back at home, I found it was Leo W7JPI calling CQ on the XW-2F transponder. Not much on that transponder, but a larger crowd on AO-85. I was able to make 5 QSOs on AO-85, and - later - upload some data to the AMSAT server.

The second station had some issues I will need to investigate, especially with the XW-2E pass. It is possible I should have brought out my second Elk log periodic, instead of relying on the crossed dipole. Even with the receive issues at the second station, it was still a good illustration of using SDR receivers for satellite work, and showing that the inexpensive Windows tablets are capable of running HDSDR and the Fox telemetry software packages.

As I write this e-mail, my uploads to Dropbox have completed. I put the RF recordings from the XW-2E and AO-85/XW-2F passes, along with some photos of my setup for the later passes and other screengrabs in separate folders there. You can go to http://dropbox.wd9ewk.net/ (hit F5 a few times, if the folder/file listing doesn't immediately show in your browser) to see those files. I didn't make a separate MP3 recording of the AO-85 pass, relying on the RF recording for my logging when I returned home this evening.

I really don't have many new observations for AO-85 tonight. I worked it on the premise that the uplink frequency is 10 kHz below what was originally published. That worked again tonight. I used narrow FM on the uplink radio, and narrowed the receive bandwidth and adjusted the audio filtering in HDSDR so I wouldn't hear any buzzing or other noises from the telemetry on the downlink. Normally HDSDR's AFC works very well with AO-85's downlink, but for several minutes the AFC kept sliding my receive frequency down to the XW-2F CW beacon just below the AO-85 downlink. I had to turn off the AFC until the two signals had more separation between them. Once the XW-2F CW beacon went lower in frequency, away from the AO-85 downlink, I resumed using AFC. I had no AFC-related problems for the remainder of the pass.

The nominal frequency of the AO-85 downlink seemed to be closer to 145.978 MHz tonight. This may complicate working this satellite for some, who may not want to adjust the downlink frequency. The Chinese-made HTs I have used would definitely need to have the downlink frequency adjusted during AO-85 passes. Some non-Chinese radios may be able to start passes on 145.980 MHz, but have to be adjusted down to 145.975 MHz for the last part of the pass. This may not be a hard-and-fast rule for all non-Chinese radios, depending on how sharp or forgiving the front-end filtering happens to be on these radios. When I worked earlier AO-85 passes with the Wouxun HTs, and the Icom IC-2820H last night, I just use the VFOs. No memory channels. I set both VFOs for narrow FM, set the 67.0 Hz CTCSS tone in the transmit VFO, 5 kHz tuning step in the transmit VFO, and the smallest possible FM tuning step in the receive VFO (5 kHz for the IC-2820H, 2.5 kHz for the Wouxun HTs).

Since I was not home for these passes, I did not try a different radio (or radio combination) for AO-85. If time permits in the next couple of days, and if the transponder is on in the evenings for western US passes, I might be able to try another radio or two before leaving for the AMSAT Symposium. Otherwise, trying different radios on AO-85 will resume after I return from Dayton, later this month.

Again, thanks to AMSAT for making the AO-85 transponder available over this weekend! It has been fun to work a satellite that's only been in orbit now for just over 3 days. I hope the telemetry and other tests are showing the satellite in good working order. And thanks to all of the stations that called or worked WD9EWK during this afternoon and early evening. :-)

73!

Patrick WD9EWK/VA7EWK http://www.wd9ewk.net/ Twitter: @WD9EWK