After having constant helicopters flying over my house, I wanted to see where they originated and were travelling to that i stumbled on ADSB, I also happen to live in close (<1nm) proximity to London Heathrow
I’ve pulled out my Raspberry pi and bought a cheap RTL device off amazon which came with a cheap whip. I was getting approx. 70 aircraft upto a range of around 100nm.
I’ve since upgraded to the FA pro plus stick and built a spider ground plane antenna where i’m now picking upto 100+ aircraft around 170nm.
A concern i have is with my signal level, i’ve installed graphs1090 and signal looks like below:
(the drop in signal above is due to me tinkering with the gain)
Having an itch to make it betterand wanting to improve is this signal any good?
The main thing with the rtl dongles is to not overload them. The pro-stick plus has both a filter and an amplifier built into it, which makes for a simple set up. From the look of that signal graph, you could probably turn the gain up by a couple of steps - you want the peak signal to be nearly at 0, but not pegged hard against it so that strong signals are lost. Have a look at the message rate graph and see what the strong signal percentage is - Somewhere between 1-5% is a good compromise.
Once you have the gain adjusted, then any improvements will likely be from improving the antenna design or its position.
I am using the blue stick as well with an optimized antenna under the roof.
Gain is set to 49.6 with the signal level below.
If i turn the gain to full power, the peak signal is getting closer to 0, but then the message rate > 3dB is increasing up to 25% which gives a decreased overall performance.
Playing around with gain is always a good starting point when the blue stick is in use. @wiedehopf is providing also an automatic script which can help finding the gain level.
i’ve experimented with several settings and 49.6 (max. manual setting) is best for me. Once moving antenna outside the building i have to reduce it.
