I have a 6.5 dBi antenna connected on a 0.3m long cable to an LNA4ALL and then into an RTL 2832U SDR dongle. I’m having trouble acquiring Strand-1. I thought I got a successful telemetry downlink, but I guess I confused it with radio static. I am using GQRX and Gpredict to compensate for doppler. Running all of this on Raspberry Pi.
I know people have managed observations on UHF omnis. I’m trying to figure out what I’m doing wrong as all I seem to be gtting is static.
To start, I had my LNA gain and audio gain set to max. I was’t getting anything so I tried Hardware AGC and still nothing, even during very close passes when the satellite was directly overhead. What am I doing wrong? Can anyone help me?
Disable hardware AGC. Set the gain slider around the middle. Find a stable signal and adjust the slider for maximum SNR.
There is tons of info on the web about tuning and using RTL dongles, so I will stick to some generic remarks:
There is no “one setting fits all” so it is important to understand how things work and be able to tune the receiver for any given scenario.
Hardware AGC will in many cases lead to de-sensing of the receiver and should only be used when a good front-end filter is used.
Maximum SNR is not the same as maximum gain. Maximum gain will in most cases overload the tuner frontend.
Using an LNA will add gain to the system and thereby reduce the gain setting where the tuner starts to overload.
You should use a stable and reliable signal to tune and test your setup. Not a satellite, which transmits sporadically what may sound like noise… Find a terrestrial source in a nearby band.