The test between sample rates has finished. It was run along the same lines as the gain test. The sample rates were changed every 10 minutes for 2 days.
First range:
As expected, there is no significant difference for maximum range.
Messages:
The message rate is slightly lower when using 12 MHz sample rate.
That is also reflected in the rate of DF17 messages received from each aircraft:
It seems that there is minimal difference at lower traffic rates, and a small advantage for the 20MHz sample rate as the traffic level increases.
Over the whole test period, the 20MHz sample rate had an average message rate 1.9% higher. Not a huge difference, so if cpu capacity, heat or power consumption are an issue, then there isn’t too much disadvantage in running at 12 MHz. For a receiver somewhere with lower message rates per aircraft (such as the US), I’d expect to see little difference between the two.
I’d be interested to run this test again should traffic rates pick up back to where they were pre-pandemic. The number of visible aircraft didn’t go above 300 or so for this test, so only ~75% or so of the previous peaks.