>       Jeff Sponaugle       j…@ecn.purdue.edu

        Jeff-

        Yes, it is legal to own and operate your own radar gun (at least
        in Colorado) The local chapter of SCCA uses them now and then to
        compare trap speeds and other things, and baseball teams use them
        to measure pitching speeds, etc., the list goes on.
        Anyway, you asked if it would be reasonable to use one to screw
        up the police radar aimed at you.  In theory this sounds like a
        good idea, however, it is not likely.  While all radar guns work
        on the same wave type (radar) and the same principle (Doppler
        effect) they do not all operate on the same frequency.  It is
        not likely the one you buy will be on the same frequency as the
        one you are trying to "jam".  The way a radar "jammer" works is
        by sending out radar waves in a wide range of frequencies, hoping
        to cover the one the gun is using.  However, because they must
        send out such a wide range, they cannot concentrate enough power
        in the one (frequency) that really matters in order to cause a
        sufficient "jam".  They rarely work, so don’t waste your money.
        Incidentally, I am not an expert on this subject, but I have read
        a few books on it, and this is the way I interpreted what I read.
        If anyone out there knows more than me and my ideas are incorrect,
        please let me know so I don’t continue making a fool of myself.

                Thanks and Happy Motoring,

                        Glenn Conser

Yes, you do need a license.  The typical license you need to obtain to
use a radar gun is a radiolocation license.  Or, you can use a K band
radar gun inside the ham band if you have an amateur radio license (Tech
class or higher) as the police K band radar guns fall into the middle of
the ham band.  You can also tweak X band guns down a bit to have them
fall into the ham 10 GHz band.

Transmitting a X/K band gun where a cop is also using a X/K band will typically
not mess up his radar.  The reason is that no two radar guns are on exactly
the same frequency.  In order to cause any interference, both radar guns
would have to be operating well within 1 MHz of each other (within the
counter/bandpass filter range), which isn’t very likely, as the design of
radar guns allows for a lot of transmitter drift.

>I
>know the power of most radar guns is in the 1 to 10 mw range.

Not quite right either.  Most radar guns have a Gunn source power output
of over 10 mw.  Typical ERP ratings are from 400 mW to 4 watts.  Some of
the older guns were 8 watts ERP.

>While jamming a radar device might be iilegal, it would be
>illegal to use a gun to monitor the speed of your own car
>for instance?  Does this sound reasonable?

No, it wouldn’t be illegal, as long as the device was properly licensed.
You can build your own X or K band radar gun to clock your own ground
speed relatively easy and inexpensively.  Obtaining the non-amateur
license probably wouldn’t be all that difficult either.

>       Jeff Sponaugle       j…@ecn.purdue.edu

                                                        — Jeff

–
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
 Jeff DePolo  N3HBZ             Twisted Pair: (215) 386-7199                  
 dep…@eniac.seas.upenn.edu    RF: 146.685- 442.70+ 144.455s (Philadelphia)  
 University of Pennsylvania     Carrier Pigeon: 420 S. 42nd St. Phila PA 19104