[FedCom] Questions

Fri, 24 May 2002 18:39:00 -0400

  Fish searching aircraft in the Chesapeake Bay use DVP on two of their 158 mhz.
business licensed frequencies.  Some TV station broadcast remotes use DVP for
obvious reasons which is so the competition cannot hear them.  Apparantly you
don't live in an area that has any DVP aircraft comms.

[email protected] wrote:

> 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.
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