From: utzoo!decvax!harpo!eagle!mhuxt!mhuxj!mhuxi!aluxz!ltn
Newsgroups: net.auto
Title: Re: BAD radar detectors
Article-I.D.: aluxz.1114
Posted: Sat Feb 26 17:03:52 1983
Received: Sun Feb 27 03:28:12 1983
References: genradbo.1547

Just a few comments regarding superhet detectors, etc.:
I don't know what sort of i.f. frequency (difference between the incoming 
radar signal and the internally-generated local oscillator signal) is used in
radar detectors, but it can't be too high (~< 200 MHz, maybe), so if the unit
is operating at 10.5 GHz, it would take a *very* good filter to stop the local
oscillator from leaking out.  Such a filter would cost much more than the
Escort.  The real way to prevent local oscillator leakage is to use a properly
designed mixer, which simply doesn't send much energy back into the antenna.
It's quite possible that those cheap, leaky radar detectors are in fact
superhet units, but they simply have scrimped on the mixer in order to save
money, and decided to let the buyer worry about the radiated signal.
(By the way marc, TV's don't really use a second mixer to get down to the
video frequency, but simply a.m. detect the i.f. to pull out the 4.5 MHz
bandwidth video.)

Les Niles  (aluxz!ltn)