PeterD wrote in
:

On Sat, 19 Feb 2011 18:34:47 -0500, "Michael A. Terrell"
wrote:



It isn't that simple. Police RADAR works by Doppler effect. I.E.,
the returned signal is mixed with with a sample of the transmitted
frequency. The difference in frequency tells your speed. Any attempt
to jam it will be a crap shoot. Even if you managed to match the RADAR
transmitter's frequency, it would still show your speed.


You know the frequency of the signal you receive. You know your speed.
Assuming you could build a circuit to compute the necessary bits, you
should have little trouble computing the original transmitted
frequency with those two bits of information. The simply transmitting
the same frequency back should result in the desired result of a lower
reading.



the active jammers I've seen program a set freq. shift to give a lesser
speed reading at the radargun. they had a switch to change it for different
speed zones.The jammer's stronger direct signal overwhelms the weaker
reflection of the gun's signal.

But white noise is broadband,so a radargun would not be able to make any
comparison to the transmitted freq. with a "white noise jammer" It would
raise the noise floor ABOVE the reflected signal,smothering it.
I believe I've seen references to radarguns having an indicator for
"jamming",and their audio output would also be an indicator,operators being
trained to recognize interference.

--
Jim Yanik
jyanik
at
localnet
dot com