Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!linus!genrad!decvax!harpo!seismo!rochester!rocksvax!dave
From: dave@rocksvax.UUCP
Newsgroups: net.auto
Subject: Re: clogged traffic and other stories - (nf)
Message-ID: <583@rocksvax.UUCP>
Date: Wed, 22-Jun-83 12:04:55 EDT
Article-I.D.: rocksvax.583
Posted: Wed Jun 22 12:04:55 1983
Date-Received: Thu, 23-Jun-83 00:14:57 EDT
Lines: 35

You need no mathmatics, just a pulse generator running at an
appropriate frequency for the band you run on and enough power to
overcome their reflected signal.  Most radars are of CW nature, that is
they transmit a signal continuously.  The receiver in the radar unit is
coupled to the transmitter such that there is a mixing of the
transmitted signal, the reference, and the incoming reflection doppler
shifted in frequency.   This produces 2 signals at the output of the
mixer, the sum of the 2 signals freq.  (20 Ghz) and a difference
signal  (audio).  The radar filters out only the low frequency
component.  This is a lot like listening to carriers on an SSB
receiver, a carrier off 1 Khz generates a 1 Khz tone out the receiver.
By putting in a pulse stream near within the passband of their receiver
you and make your own audio range signal, which is basically
indistinguishable from the transmitter-reflection signal.  There will
be a small piece of the normal reflection signal modulating your audio
signal, but the digital limiting in the frequency counter will probably
filter out that small interference, looks like noise on the edges of
square waves.

If you run the same power as the police radar, very easy seeing most of
the Gunn diodes are the same, you can easily jam/have the radar read
anything you want.  Let me note that only hams can legally send these
transmissions, as long as you identify on morse code at the appropriate
intervals and stay within our bands.  K band no problem, we share that,
X band is an adjacent band, ends @ 10 Ghz, radar operates @ 10.250 Ghz
I think.

I still think the ultimate ham project is to build a moving radar, to
find out how fast that RX-7 passed my diesel Rabbit by.  Of course that
"calibration" pulse generater would be fun to play with, imagine plodding
by a radar trap while their radar reads 98 MPH!! 

Dave Sewhuk
Arpa: Sewhuk.HENR@PARC-MAXC
uucp: {rochester, allegra, amd70}!rocksvax!dave