Today on Aye Gill Pike G/NP-023, no 3 signal at all, a marginal O2 signal such that I could get a GPRS connection just. Enough to send an SMS. but no more.
My Icom E91 jams my Garmin Oregon when tuned to my local D-Star repeater.
Best explanation I’ve been able to come up with is that the 3rd harmonic of the LO falls within the GPS spectrum and de-senses the receiver. The point here is that even though the GPS signal is very broad and below the noise, just one strong narrow interfering signal can knock it out. This is a consumer grade device; doubtless a military grade GPS receiver would fare better, but correlating the GPS signal in the face of a strong peak in band may be a challenge.
Of course my explanation may be wrong, but the effect is real enough and 100% reproducible.
Martyn
I’m sure Andy knows more about this than I do, but I believe one cause for this effect when you are at a high spot is that the phone sees a strong signal from a base station that is too far away for the mobile to be able to meet the timing constraints for the channel time-division multiplexing.
Martyn
The other issue that I have found is that on some summits in certin areas you can be above the mobile service which is beamed up the valleys. The signal appears as you descend. I now carry two mobiles on different networks, but while that gives a modicum of flexibility for spotting, it doesn’t help with having a connection for the purposes of being “legal” on 60m. Only my main phone on O2 is registered.
Maybe they could, you know, use the frequency we’re using to ask us to stop and QSY. To guarantee we understood their request they could use the simplest method of RF comms and key a carrier on and off to send the message. If we developed a code for this on / off keying and everyone took a test to show they understood it, then we could use their frequencies till they asked us to QSY.
Is this worth chasing up with OFCOM?
Brilliant. What could we call his method?
g6lkb
No idea. How about something like MOD Observation and Reporting Service Experiment?
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MODORSE! I like it 
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