Ok, posting for a little help…I am seeing very low DBFS (highest is about -17 or so when planes flying directly overhead. I am seeing planes 40 miles out max.

Here’s my setup, Raspberry PI and RTL2832U, homebrew 1/4 wave groundplane mounted about 30’ above ground. 100’ RG8X coax run to hamshack. I do have lots of trees and live in a lower spot, however, still no idea why signal strength is so low.

I’ve tried adjusting gain…no better results
Shorter coax length…no better results

Any assistance would be much appreciated.


15db loss using RG8X.
That is a lot of loss, 97% using Coax Calculator
Try moving the RPI closer to the antenna(power by POE or use WIFI) and using a shorter coax run.
Or you could use better coax. I use LMR400 but it isn’t cheap.

Or you could use an amp powered by bias-t (See uputronics and others).
This would allow you to use the current coax.

A filter could also help but the numbers are low so it will lower them even more(2-3db I think for the FA filter).

The FA pro-plus dongle has a built in filter(1090Mhz) and amp. Another choice.

Your range is horrible(I see receivers near your with a lot more aircraft). I got better than that with the RTL-SDR supplied antenna on my basement window bars. Could the dongle be faulty? Have you tried a different dongle.

Thanks for the quick reply. I can move the setup and significantly shorten coax. I can also go to RG6 or 11.

Thanks for the suggestions…I’ll keep tweaking and report results. Thanks again…

Wow…I should have known. Shortening the coax helped quite a bit…went down to 25 ft. Many more planes. Like I said, I’m in a really low spot with tall white oaks…

Going to continue with your suggestions…thanks!

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Trees are big attenuators at these frequencies. According to coverage prediction sites I should have great range in a 270 degree arc, but for the trees it might be correct.