[time-nuts] gps jamming source found

[ed breya]

The wireless data links in those R/C sensor type things don't operate 
near GPS carriers, but their harmonics can land there. The 
transmitted power allowed should be too small to interfere with 
anyone's receiver farther away - yours is probably pretty close. I 
believe that the remote senders do not wait for any polling signals - 
if so, they would have to be receiving on a regular basis, taking 
precious battery life. It makes more sense for them to just burst 
transmit at regular intervals, while the line-powered (or 
bigger-battery-powered) base station is always listening, or listens 
at various intervals to see if any remotes are calling. That's why it 
takes a while to get the initial temperature data when the system starts up.

The base station receivers used for simple, cheap VHF data are 
typically super-regenerative type for high sensitivity, so when 
they're fired up it may appear that they're transmitting, but 
actually are only receiving, with lots of crap kicking out of the 
super-regen circuit. A common carrier used for VHF remotes is around 
315 MHz - the fifth harmonic of that one is especially bad, landing 
almost right on top of GPS. When you add in the loose frequency 
stability and modulation, and the regen signals, the transmitters and 
receivers can cause quite a spectral mess.

Ed