KO4MA sez:
Notice the Doppler curve is different between the three on the right.
As I see it, the one in the center of those three ( (435.881) indicated as almost exactly in position to translate via AO-51 to the 145.92 downlink..) is already more like ~2 min past TCA (at the base line).
I would expect anything coming out of FO-29's transponder to show the same dopppler rate as the other signals, say the beacon at 435.795 ...
Unless it was going thru yet another satellite first ..!.. Or possibly not going thru FO-29 at all, but heard direct from a 2nd bird. SO-50 was just ahead of AO-29 on that pass. Hummm...
Even tho the AO-51 uplink has already been changed, I may try and grab a waterfall tonite centered on 435.850 ... Just to see if there are two different doppler rates again. Very Interesting . . . /;^)
I would expect anything coming out of FO-29's transponder to show the same dopppler rate as the other signals, say the beacon at 435.795 ...
I may be misunderstanding your statement, but transmitters in different locations on the ground will show different curves. Remember you have Doppler on both the uplink and downlink too, so the beacon should be different than any uplinked signal (unless someone was running full Doppler tuning).
73, Drew KO4MA
I would expect . . . .
I may be misunderstanding your statement, but transmitters in different locations on the ground will show different curves. Remember you have Doppler on both the uplink and downlink too, so the beacon should be different than any uplinked signal (unless someone was running full Doppler tuning).
73, Drew KO4MA
Point well taken Drew - Thanks for your thoughts. I figured there would be some slight differences in uplink doppler as a function of ground location relative to TCA. Comparing the other traces to that of the presumed beacon, there appear to be two slopes - either matching closely or not. That made me suspect an additional transmitter. The 145 MHz doppler I would expect to be less pronounced than the 435 ... I suppose with a really clean display and accurate measurements and .. .. ..
I'm sure that an entire team of experts is involved in this type of spectral fingerprinting every day. Wish I had more time and tools, it could be a lot of (admittedly geeky) fun. Unfortunately the only waterfall I can get is an audio passband-width ala MixW or similar. The wideband waterfall you showed looks like an interesting tool. I'm envious.
Anyway, changing the uplink solves the immediate issue, but still leaves the question - could it have been a terrestrial carrier, relayed by FO-29 or possibly a spur from some other transmitter on a different bird... The fact that you saw energy on that frequency, with doppler could fairly well rule out a ground-based signal on the 145 MHz uplink, reckon ?
Thanks /;^)
I would expect ...
I may be misunderstanding your statement ...
I'm easily mis-understood. Like in my 'just-sent' reply - I said...
The fact that you saw energy on that frequency, with doppler could fairly well rule out a ground-based signal on the 145 MHz uplink, reckon ?
Too few words failed to express what I thought I was thinking. I'll try again.
The fact that you saw energy on that 435.xx, with doppler could fairly well rule out a ground-based signal on 435.xx as the source of interference to the AO-51 uplink. I think that is what you were confirming.
Maybe thats better. Maybe additional coffee may be required .. /;^)
participants (2)
-
Alan Sieg WB5RMG -
Andrew Glasbrenner