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Re: [Discuss-gnuradio] Homing in on the mystery of Pulsy McGrooder

From: David I. Emery
Subject: Re: [Discuss-gnuradio] Homing in on the mystery of Pulsy McGrooder
Date: Tue, 12 Sep 2006 01:25:01 -0400
User-agent: Mutt/1.4.1i

On Mon, Sep 11, 2006 at 11:30:47PM -0500, Rick Parrish wrote:
> *giggle*
> Marcus ... that's an aircraft transponder. Except for some vintage 
> 1930's aircraft that don't have an electrical system - every plane / 
> helicopter has one. Hit Google or Yahoo! for "Mode-C" and "Mode-S" 
> transponder.
> The ground radar "pings" the aircraft's transponder (interrogation). The 
> transponder sends back a reply. Some replies carry a 12 bit ID code plus 
> altitude. Others might have actual GPS coordinates.

        The transponders are 1090/1030 mhz and not 1350.   1350 is just

        Also FWIW, TACAN and JTIDS systems operate between 960 and 1240
mhz with pulsed emissions as well as radars.

        But Marcus's description of signals every 5 seconds sounds exactly
like radar and I bet if he has ID'd the right radar as the culprit he
can go visit it and watch it turning around at exactly the interburst
interval he sees.   That might in fact be a good test if he cannot find a
better method of verifying that is his radar as various actual radars tend
to use different antenna RPMs.

        I might also add that unless propagation is strictly line of sight
one needs more sophisticated path models to determine expected signal power.
-11 dbm sounds rather loud.

   Dave Emery N1PRE,  address@hidden  DIE Consulting, Weston, Mass 02493
"An empty zombie mind with a forlorn barely readable weatherbeaten
'For Rent' sign still vainly flapping outside on the weed encrusted pole - in 
celebration of what could have been, but wasn't and is not to be now either."

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