[time-nuts] time-nuts Digest, Vol 24, Issue 47

[SAIDJACK at aol.com]

Hello Faisal,
 
a small annecdote about GPS jamming from the design of our FireFox GPS  
Disciplined synthesizers:
 
We have a broadband synthesizer driven by a GPSDO on the same PCB. This  
synthesizer would completely swamp out the GPS receiption if you set it to  
1574MHz CW output, the on-board noise was so powerfull (the output of  the unit can 
be set from DC to 1640MHz). Our output can go up  to +18dBm, millions of times 
more power than the GPS signal itself...
 
The effect was that the M12+ receiver would just loose lock within a +-5 -  
10MHz bandwidth around the GPS carrier. The receiver would show 0 sattelites  
being received. As soon as you set the frequency outside of this  band, 
everything was fine. 
 
We improved this by putting the GPS board into a metal shield. So the  effect 
of noise generated inside the enclosure was greatly mitigated.
 
But the CW power radiated by the BNC connector itself on the unit is still  
enough to find its way to the antenna 10 meters away and about 3m above it, and 
 swamp the signal!
 
Putting a small paperclip into the BNC RF output connector at +18dBm at  
1574MHz would probably cause a couple of blocks in our neighbourhood to loose  GPS 
lock :)
 
Never tried this and never will of course.
 
bye,
Said