Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!rex!ginosko!uunet!zephyr.ens.tek.com!vice!georgep
From: georgep@vice.ICO.TEK.COM (George Pell)
Newsgroups: sci.electronics
Subject: Re: "Spybuster" AD COPY
Message-ID: <4022@vice.ICO.TEK.COM>
Date: 23 Aug 89 17:16:52 GMT
References: <17100002@inmet> <647@anasaz.UUCP>
Reply-To: georgep@vice.ICO.TEK.COM (George Pell)
Organization: Tektronix, Inc., Beaverton,  OR.
Lines: 42

In article <647@anasaz.UUCP> john@anasaz.UUCP (John Moore) writes:
+In article <17100002@inmet> newbie@inmet writes:
+>   *** EXCERPTS FROM SPYBUSTER AD COPY ***   
+>A TRACKING  COMPUTER -- Spybuster .....  receives signals 
+>from the FAA's ground-based aircraft surveillance system.  
+>It then computes that plane's closing rate relative to your position.... 
+
+This actually looks like a fairly practical technology within
+certain limits: the aircraft has to be within range of the
+FAA IFF interrogator's, and there can't be too many aircraft around.
+Here in Arizona many highways are out of range.
+
+The ironic thing is that I would probably use one IN an airplane
+as a collision alert detector.

I suspect that the skybuster only receives replys from aircraft
interrogated by the Air Traffic Control Secondary Radar Beacon,
and judges distance from signal strength.  I do this with my Pro2004
scanner, and it's reception range is about 5 miles.

Radar Beacon coverage at low altitude <1000 feet is spotty at best,
and at ground level reception of the interrogator pulses would be 
totally undependable.  The skybuster would require receiving both 
the interrogator and the reply pulses, and would have to measure 
the delay between them to actually calculate speed and distance.

As for using the skybuster as an anti-collision alert detector, It
would respond to my transponder located in my airplane, and would
ALWAYS be issuing a warning.  In order to be effective, you would
have to turn off your transponder, which is not especially a good
idea in high traffic density areas where you could use a collision
alert.

Keep in mind that a large percentage of private aircraft operating
under visual flight rules follow freeways (freeways are called
cement VORs).  I expect that the skybuster would issue 99.9% false 
alarms.

geo
N29531
Cessna Cardinal 
"I Follow Freeways"