[FedCom] Questions

Thu, 23 May 2002 18:43:01 EDT

In a message dated 5/23/02 11:13:57 AM Central Daylight Time, 
[email protected] writes:

<< Why can't most (if not all) surveillances with aircraft talk coded? 
 Does it have something to do with synchronization?? >>

I don't recall ever hearing aircraft, particularly helicopters using DVP/DES. 
As near as I can figure (and I'm certanly no expert), it might have something 
to do with the rotation of the main rotor. 

I know a lot of electrical energy is produced by a spinning rotor, so perhaps 
there is too much noise for DVP/DES to function, i.e. to deconstruct an 
analog transmission, convert it to digital and send it off, or vice versa. 
That may also be one of the reasons that the military went with 
frequency-hopping radios rather than encrypted radios in their helos. Of 
course frequency hopping is also more resilient to SIGINT attempts.

I also wonder if it's a matter of all the other noise in the RF spectrum. 
Look at your average congested area: a cacaphony of spurious junk. 

164.5500 (167.9 PL) (simplex) was in use in the skies over Chicago the other 
day. It's ordinarily encrypted, but obviously this wasn't possible this time 
out.