Thoughts on optimizing gain

[obj]

@caius

This also shows the major limitation in performance of the RTL dongles - as the number of aircraft increases, the ability of the decoder to discriminate crosstalking aircraft is reduced, falling off sharply over 200 aircraft. I would expect a receiver with higher dynamic range and better sample rate such as an airspy to do much better here.

You may have more than one effect going on here.

1. SSRs have a time budget for interrogations; above a certain number of aircraft, this budget will limit the interrogation rate per aircraft (& therefore response rate)

2. IIRC TCAS dials back transmit power when it sees a congested environment, so again fewer replies per aircraft as the effective interrogation range is lower.

It might be interesting to plot only ADS-B messages, since the transmit rate of those messages should be mostly unaffected by the environment. I don’t think that’s a statistic that’s currently collected though.