[time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)

Chuck Harris cfharris at erols.com
Mon Nov 16 00:11:14 UTC 2009


Magnus Danielson wrote:
> Chuck,
> 
> Chuck Harris wrote:
>> What makes you think it needs to be CW, and cannot be pulsed and
>> chirped?
> 
> May I roll in a noise jammer into the debate?

Absolutely!  They can be extremely power efficient.  Raise the noise
floor in the vicinity of the receiver, and it is all done.

Probably the easiest solution would be to take a PN source and use it
to drive a pulser that pulses a chirp oscillator.  If you are feeling
really polite, you could put a bandpass filter on the thing to protect
other services.

>> All it has to do is confuse the receiver enough so that you can't
>> trust its readings.
> 
> Depends on the goal. For some strategies, blackout is the goal, for some 
> getting the readings go haywire every once in a while suffice.

Agreed!

My 9V battery suggestion was for a localized blackout device.  You only
have to make the receiver question each satellite's signal often enough
for it to rule it out.  No way is CW necessary, or even desirable.

As John suggested, someone (say the Chinese) could put these things in
battery operated stuffed animals, and set them up to jam a little bit
now and then.  After Xmas, the GPS landscape would be littered with these
little stealth jammers, and willing supplicants to replace their batteries.

-Chuck



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