Rick Wilson
EF0
My Garmin GPS 76CS worked flawlessly for a number of years. Out of nowhere, it stopped working. Almost zero signal for any bird in my driveway which was a known location for good reception. Position on the vehicle's dash and all wiring remained the same.
OK, what has changed? Ah! A frequency change used by my local (and brother's workplace) Medivac helicopter service had been programmed into my VHF Motorola Spectra (also used for HAM) radio. I was listening on that channel.
Apparently the two-way radio receiver's IF was radiating a harmonic that was desensing the Garmin receiver making it useless. Unusual for a commercial radio. Changing channels or simply moving the radio microphone made a difference in the received signal strength on the GPS. Ferrite toroids on the mic cord and power leads fixed the issue.
Moral of the story is that the GPS signal is extremely weak and the receivers are very sensitive. If you GPS signal inexplicably goes away, begin diagnostics by turning off *all* in-car electronics one-by-one and look for the culprit.
OK, what has changed? Ah! A frequency change used by my local (and brother's workplace) Medivac helicopter service had been programmed into my VHF Motorola Spectra (also used for HAM) radio. I was listening on that channel.
Apparently the two-way radio receiver's IF was radiating a harmonic that was desensing the Garmin receiver making it useless. Unusual for a commercial radio. Changing channels or simply moving the radio microphone made a difference in the received signal strength on the GPS. Ferrite toroids on the mic cord and power leads fixed the issue.
Moral of the story is that the GPS signal is extremely weak and the receivers are very sensitive. If you GPS signal inexplicably goes away, begin diagnostics by turning off *all* in-car electronics one-by-one and look for the culprit.
