Hello. My SatNOGS station (id 680) has been succesfully operational for quite a while now but over recent weeks any UHF observations have failed to get any data. I have a single turnstile VHF/UHF antenna at the peak of my house roof. This feeds a metal cased RTL SDR which is attached to my Pi 3 by a short USB cable. The feeder is solid core, low loss coax about 10m long. I’ve looked at the SWR on the feeder with my Nano VNA, it gives a figure of 1:2.4 at 437MHz and 1:2.5 at 137MHz, unfortunately I don’t have benchmark figures from when things were initially installed but these readings appear good to me? Where should I look next to try to get the UHF observations back please? Richard M0RSX
Those SWR figures are fairly high, at least for an antenna that you might want to transmit into. Generally you’d be looking for less than 1:1.5 to keep most transmitters happy.
As for not seeing signals on UHF, looking at your stations recent observations I’m not sure the satellites you have been picking are transmitting reliably.
I’d suggest using some of the sats listed here as tests: Omnidirectional Station How To - SatNOGS Wiki
(Note that FalconSat-3 isn’t as good as it used to be, and is off sometimes).
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I’d also recommend testing the rtl-sdr against known local signals to see if the receivers sensitivity has changed. Then move onto the cabling/rf adapters (LNA?). Occasionally I have to ‘unplug’ my rtl-sdr v3 because observations just start failing.