Just wanted to share some testing results, plus maybe someone who does more rf engineering can explain one of these results.
First image, my local spectrum through an unfiltered sdr card. Tons of noise, so I wanted to try some filters and an amp to reach out past 150nm or so.
Next, the output from the ADSBX blue stick Dongle
(btw this card plus their antenna blows away everything else I tested. four sdr cards, 6 antennas, getting 250+NM range from a ground level mount between some houses)
Still some noise in there from the cell phones so I slapped on one of the adsbx filters in front, Filter link now we have progress!
That combo will be my main stick for now. It gets super hot though, I’m working on an enclosure with enough fans and vents.
Here’s the weird part of testing that I want to understand better.
This is the regular sdr (stratux) from the first image, with one of these china LNA Filters on it. Gain set to 30. Blown out the whole thing. Terrible plane finding. Janky LNA
So I turned down the gain a LOT to 10, and I’m getting clean of the noise, but what is the thick signal from 1060-1120mhz? At this gain level I’m getting the same signal levels as I did with nothing plugged in at all, dead even, plus it’s much less reliable, missing lots of planes my other receiver sees. Is this just jamming itself trying to amplify everything around the 1090 range? Either way, warning to others, spending $20 on an amplifier you get what you pay for!
So for now the high power solution I’m running will be the adsbx stick, filter and antenna. Total price $100. (+$15 for the rpi 02w) I was hoping to find a stick with a built in amp and filter (that actually filtered), and use the ground plane antenna I built and tuned, but I can’t get close to those results yet. The other one will go on the south side to try and fill in a gap I can’t close yet.
I’d love to see a repository of peoples spectrums, before and after installing different dongles, amps, filters, etc. I’m happy to keep testing here, still waiting for one more dongle that was late. Would be nice to narrow down what works and what doesn’t, especially with all the no name options on aliexpress and amazon.