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by Vitamin_Sushi 22 days ago
I love learning about nav aids on planes. One thing I didn't quite understand was the DME interrogation: "To handle conflicting pulses, each aircraft deliberately jitters its interrogation timing at random, then keeps only replies at a constant lag after its own pulses."

Does this mean that the pulse pair itself was jittered? As in, plane A sends a pulse pair, say 10us between the pulses and plane B sends a pulse pair 20us apart. The DME then responds with the same pulse pair delay and the planes listen then calculate the responding pulse pair to figure out which one is theirs?

1 comments

The pulse pairs themselves are always 12 us apart. The jitter comes from the aircraft sending interrogations at random intervals in a steam, so that it can discern which returns are at at the same interval as the ones that were sent. I can make the animation more obvious for this -- on my to do list :)
Oh, now that makes more sense, thanks!