On Aug 19, 10:55 am, "John R. Copeland"
wrote:
"Paul Tomblin" wrote in ...
In a previous article, said:
How does the system know which are the outer dme "targets"? Is it
just the weaker dme transmissions that are received by the ground
station that are dropped? Stan

By response time. It sends out a signal, and the first N to respond are
tracked.

--

No, Paul, the DME ground station does not initiate the exchange.
The ground stations only reply to interrogations from aircraft.
See Bob Noel's correct explanation elsewhere in this thread.
When the ground station is not being interrogated, it increases
its receiver sensitivity until it "replies" occasionally to random noise.
As more actual interrogations are received, the ground receiver
reduces its sensitivity to limit the rate of replies transmitted.

Back when I was about 18 years old I had a guy on a construction crew
tell me that his radar detector worked by sending out a beam which
intercepted the beam of the cops radar and that is how it detected
it. When I tried to explain that it didn't work like that, but simply
received reflected signals which is why it could detect a cop over a
hill, he dismissed my explanation and stubbornly stuck to his
idea... :-)