First, sorry if there’s already the solution somewhere, but I have not found it.
I have a setup with Antenna → LNA from rtl-sdr.com → 10m of TV cable → rtl-sdr V4 dongle.
My RTL SDR gain is set to 25dB.
My issue is that based on my last observations, (example here: SatNOGS Network - Observation 12295360 ), I feel like the LNA is not active. Note: Testing at home gives me a low portion of the sky visible, mostly between 225° and 135° azimuth, above 15 to 20° of elevation.
The way I activate the bias-T is by following the tutorial here: Software Defined Radio - SatNOGS Wiki , under " Using RTL-SDR.com V3 Dongle’s Bias-T Power Supply". It uses pre and post scripts, which worked (or at least did not make an error) when I tested them outside of a satnogs observation.
It dates back from 2019 and I have the V4 and not the V3. I don’t know if that’s important. I also added “biastee=true” in SATNOGS_DEV_ARGS.
I know the LNA itself works because if I go to SDR++ and activate “biasT”, I can clearly see the change.
Does someone know what is the standard 2025 procedure of turning on the biasT during an observation?
Try setting SATNOGS_SOAPY_RX_DEVICE to driver=rtlsdr,biastee=true.
Usually when a simple lna is off, you get pretty much no signal at all, so I’m not entirely sure that this is the case.
Running the same lines as pre and post script in satnogs-setup does not work.
SATNOGS_SOAPY_RX_DEVICE = "driver=rtlsdr, biastee=true", as you suggested, works for turning the biast on, but it leaves it ON forever, not shutting it down after an observation.
So I got automatically turning it on figured out but I have yet to find how to shut it down after an observation.
The older drivers didn’t touch the bias setting, so running that command before launching a flowgraph didn’t reset it, that isn’t the case anymore. And it also depends on the soapy version and what sdr we’re talking about.
If you want to turn it off after observation, you can put that command in the SATNOGS_POST_OBSERVATION_SCRIPT, if it’s the dockerized client you can maybe use this command instead SoapySDRUtil --probe=driver=rtlsdr,biastee=false, and to make it silent, add > /dev/null 2>&1 to the end of that.
But to be honest, I do not turn the LNA off between observations, ymmv.
I can see that you’re running client version 1.9.3 and raspberry pi, but on what installation type ? rtl_biast should be availiable in the docker images already, the newer packages already include it, so why did you end up needing to build it ?
If you can’t answer these questions, maybe just try put rtl_biast -b 0 in the SATNOGS_POST_OBSERVATION_SCRIPT, do not add any absolute path.
