Tom Clarke w4okw at GMPEXPRESS.NET
Tue May 30 23:14:01 EDT 2006

kd4e said:

> FM would work well, but it suffers from capture effect. If two stations 
> transmit simultaneoulsy, one could cover up the other and it might not be 
> realized. AM will give a heterodyne under many conditions where FM won't.
> Advantage: AM
----------Tom Sez-------------------------
I  have experienced this many times.  When a "double" occurs, the resulting 
heterodyne (no two aircraft radios are exactly on the same freq!) makes it 
apparent that a transmission was blocked. Someone usually pipes up with 
"blocked!" and the controller repeats.  Crude, but effective.

>If every airplane listened to every other one they'd
>be terribly confused.

----------Tom Sez---------------------------------
Actually there is an advantage to the "party line" here. It is a great 
method of maintaining "situational awareness".  By listening to all the 
other aircraft (in your general area, not the whole country, obvioiusly), 
you can maintain a "mental plot" of where everyone is in the pattern or 
along the airway in your sector.   It is fun to quiz your copilot by asking 
him "what altitude was that Delta 75 at"? Just to see if he is aware of the 
guy climbing up behind you and leveling a thousand below!!  Grammatically 
atrocious, but an interesting exercise.
>When I am in an airport monitoring traffic I observe
>multiple frequencies with multiple conversations.
--------------Tom sez---------------------------
You bet!  Trying to listen to ground, tower, and approach control would be a 
nightmare!  You wouldn't have any SA at all!

BTW HF Aeronautical switched to SSB years ago for all the good reasons 
prevously noted.  That little Collins box down in the avionics bay, that 
puts out 400W PEP is a wonder.  Can you imagine the size of a 400 watt AM 
rig?  You would have to leave a couple of Pax behind or some gas!

Try 5598, 8946, 13306 on the East coast and 10051 for New York and Gander 
weather broadcasts.  11175 is an interesting mil frequency too (Andrews 
among others).

73 de Tom/W4OKW
Just a kid with 15,000 hours "breaking the surly bonds". 

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