FlightAware Discussions

How many squitters per second?

Hi!
How manu squitters per second Pro Stick Plus can handle? Also, this is a hardware or software limitation? In case of software, how many squitters per second Orange feeder can handle?

Same rtl-sdr receiver, just one with a filter and one without.

The rtl-sdr receivers lack dynamic range which is one limiting factor.
For best reception you also need more oversampling than the rtl-sdr receivers have bandwidth for.

Anyhow the maximum message rate depends a lot on the ratio of ModeA/C to ModeS messages, as the ModeA/C messages are on the same frequency.
Then it very much depends on radar interrogation rates.
Usually a rtl-sdr receiver in the US can reach more positions per second compared to Europe because there are more All Call replies (DF11) in Europe.
But the message rate will be higher in Europe, not that that is necessarily useful as is easy to understand with less positions per second.

Under perfect conditions with all the messages on 1090 MHz being ModeS, sufficient SNR and not overlapping (impossible in the real world), i’m sure you could have quite a high message rate. You could even calculate such a rate quite easily but it’s not really interesting.

I think diminishing reception due to overlapping messages really kicks in around 1200 or 1400 messages per second.
With enough messages in the air, you can probably reach around 2000 messages per second with the rtl-sdr. (EDIT: probably around 1700)
Better receivers go up to around 3000 messages per second. (Radarcape, Airspy)

Using directional antennas and multiple receivers you can probably surpass those limits, but that’s not a single receiver anymore.

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I think that’s probably a bit high - The absolute maximum I ever saw with an rtl dongle was about about 1800/s with 1600-1700 more typical.

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I saw some calculations somewhere that were indicating around 1800 msg/sec as a limit due to the packet collisions.

I’m sure I never saw more than 1,800 msg/sec with an RTL SDR

I am using the blue Pro Plus stick in a busy area. Last six months only a few peaks > 1300.

This might be the limit of this stick.

That’s what I used to run, it would do 1800 but as said, I’m pretty sure I never saw higher.