[amsat-bb] AO-7 Mode A anomaly
aa5am at arrl.net
Fri Feb 4 19:55:22 PST 2011
Has anyone experienced anything like this on AO-7 Mode A?
Earlier today on pass 65777 ( AOS approx. 2207z) I was looking for my downlink signal shortly after my AOS. While searching for my downlink signal I could also hear a few other unidentifiable CW stations. I figured they were also looking for their downlink signal since it was in that part of the downlink passband where I usually find my downlink signal (29.452-29.454 MHz). I could finally identify one of the CW stations as W8TK. He kept sending his call and jumping around in frequency a little. I called him several times but to no avail. A few minutes later I heard a weak SSB station and heard the call WA7TFZ. I didn't hear anything else so I began calling CQ and had no replies for the remainder of the pass. I finally lost my downlink signal but still had a few minutes before the bird went over the horizon.
I began tuning around and found 2 more CW stations one was W1MO and K7NJ this was about 2-3 minutes before the predicted LOS. They were high in the passband around 29.468 MHz. I could clearly copy K7NJ and he was calling CQ FOC. I copied the CW signals until just a little after the predicted LOS when they faded into the noise. I listened for several minutes after LOS and never heard any other signals.
I thought that this was very strange for several reasons:
1. 4 new calls on AO7 Mode A ( Not a bad thing but very unlikely)
2. Only hearing stations shortly after AOS and just before LOS.
3. Stations operating high in the passband.
4. One station was calling CQ FOC.
I started wondering if maybe I had a common window with both AO7 and VO52 since VO52s downlink overlaps AO7 mode A uplink. Threw this out real quick after seeing that VO52 was half a world away.
I emailed W8TK and asked if he was on the satellite. He said that he doesn't have any equipment for bands higher than 10m and that he was on 20m CW chasing DX about that time. I also emailed W1MO but haven't heard back from him.
I've played around with the numbers a bit but it doesn't appear to be a harmonic of one of the lower bands but maybe more like some oddball mixing product. I haven't ruled out something in my radio not working properly but have never heard anything like this before and only seemed to be present when the satellite was in view.
Anyone else have similar experience?
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