Observation 1516001: OSCAR 7 (7530)

Yesterday I built my first ground station. I scheduled a few observations.

The station is currently located indoors on floor 2 of a 5 floor brick building, and the antenna isn’t tuned, so I’m not expecting a lot from the observations. The plan is to tune the antenna and move the station to a mast on top of another building.

Observation 1516001 shows something received, that shifts higher in frequency during the observation. The signal is faint, but it looks to me like other observations also experience this shift.

Is there something I should do to investigate, or should I just focus on getting the antenna tuned and mount the station at the new location? The location is remote, so I won’t have many opportunities to reconfigure it once it has been deployed (except doing software adjustments through ssh).

I could bring the station to a place nearby (with open view to the sky) for a pass or two. I would then power it using a USB powerpack and let it connect through my wireless hotspot. I’ll probably to wait until it is not raining though.

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The faint signal you see that gets higher is terrestrial in origin. (as your station tunes for doppler, from highest to lowest, terrestrial signals will move in the opposite direction).

There is no evidence of AO-7 there, and I wouldn’t expect any being that the antenna is buried inside a building and AO-7 is very weak. I don’t think that the UHF beacon even works any more (AO-7 only works in full illumination - and then I think the only working transmitters are the linear transponders).

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Thanks for explaining. I wasn’t aware the station tunes for doppler. I assumed the station used a wide enough bandwidth, kept the center frequency fixed during the observation and adjusted for doppler in software. I took a new look at the examples at https://wiki.satnogs.org/Operation and they make much more sense now.

Is there a better way to find which (UHF) satellites have strong signal, except filtering for “success rate” in the pass predictions?

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I’m not really familiar with all the UHF sats, only the amateur radio ones for the most part. NO-84 (PSAT) has a strong UHF downlink, as does FalconSat-3. However I suspect FS-3 will never get very high over your horizon. I’m sure the SatNogs guys will have better suggestions.