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From: wolfgang@wsrcc.com (Wolfgang S. Rupprecht)
Newsgroups: sci.electronics
Subject: Radar detector internals?
Summary: hacking a radar detector
Keywords: radar detector hardware hacking
Message-ID: <1991May9.152259.8545@wsrcc.com>
Date: 9 May 91 15:22:59 GMT
Organization: Wolfgang S Rupprecht Computer Consulting, Washington DC.
Lines: 35

Curiosity just got the better part of me and I decided to see what
makes my radar detector tick.  The model is a Whistler-303 superhet
X/K band unit.  It is composed of two modules: a pc board with three
leds / switch on it, and the RF horn and detectors.  The only real
components on the led board is a Motorola SC94437CP chip and an 8v
regulator.  The two modules are connected with 4 wires.

	1) +12v
	2) 0.6 v  (rf detected signal out ??)
	3) 5v pulse - 1.2ms high, 50ms low, 0.3 ms frame rate jitter
	4) gnd

The pulse line is a big mystery to me.  It appears to be a line that
can be momentarily grounded to go into city mode, or momentarily
sorted to the regulated +8v to go into "dark mode".  At least I think
that it is dark mode toggle - the leds all go off.  (There is an
unpopulated section of the PC board where this switch would go - so I
tried it to see what would happen.  When it goes into dark mode, the
current drawn from the supply stays normal, so I assume the device
isn't going into latch up.  ;-) )

The RF module has a 5v regulator on it, and 4 pin-filters lead the 4
signals into the RF module.  I was hoping to find a an obvious sweep
signal and a detector signal so that I could display Frequency vs.
Amplitude in x-y mode on a scope.  I guess that is all buried deeply
in the RF "can" section where I can't easily get to it.

I as still puzzled about the "pulse" signal passing between the two
modules.  Does anyone have any info to shed light on this mystery?

-wolfgang
	
-- 
Wolfgang Rupprecht    wolfgang@wsrcc.com (or) uunet!wsrcc!wolfgang
Snail Mail Address:   Box 6524, Alexandria, VA 22306-0524