Noise on observations + how to improve reception

SatNOGS
1

Hello SatNOGS community,

It’s been a few months since I have a lot of noises on the observations on my SatNOGS ground station. You can see that noise on this observation for example: SatNOGS Network - Observation 13736733 At first I thought it was FM radio (98-108MHz) so I added the RTL SDR FM notch, but there was no improvement.

So my setup is: QFH antenna → FM Notch → RTL SDR LNA → RTL SDR → Rpi

I made the QFH antenna myself last summer. I did not do a balun with the coax cable, like it is showed on this tutorial. Could it be that the noise is because I don’t have a balun ?

More generally speaking, why do we need a balun to a QFH antenna, even though the antenna strand are not the same size.

My second question here is: I feel my station performances are poor. I checked my antenna with a nanoVNA and reached only around -11 dB in the S11. I have seen QFH antenna with S11 of -15 dB or lower. The gain of my RTL SDR is set to 20.7 dB. The Rpi is communicating with Wifi, there is no PoE.

Playing on this variables, how can I improve my station’s sensitivity to decode more satellite ?

Thank you !

Arykno

1 Like
2

what i know, the balun is to choke the noise from cable. so it should be put after antenna as close as possible. (ussualy with wind the coax around your qfh pvc tube)

maybe you can try with this:

QFH antenna → RTL SDR LNA (put it as close as after antenna) → balun choke (the simple way: just wind the coax around pvc tube) → lenght cable to your raspi (for the best result not more than 4 metre for UHF) →FM Notch (optional) → RTL SDR → Rpi