Just thought I would update all on a problem that I have finally solved.
I recently had an ADS-B system installed in my Cessna 180. I installed a Garmin GTX-345 and connected it to my Garmin GNS-650.
During testing to meet the compliance requirements and get my $500 rebate I had a problem keeping the 650 from losing satellites. It only occurred in flight and it was intermittent. All the satellites would drop out and the 650 would then re-acquire in about 1 minute. I couldn’t pass the compliance test.
After several more flights, switching antennas, turning off various other devices, swapping out the 650 and replacing the 650’s antenna, I finally figured out what the problem was.
The culprit turned out to be my SPOT Gen3 locator.
The reason I didn’t think it was the SPOT was that it has caused no problems in the last 3 years that I have had it in the same location, on top of the panel’s sunshield. Apparently, the added 345 and associated wiring influenced the RF absorption from the SPOT that it blanked out the GPS signal to the 650 when the SPOT would transmit position or messaging information. Since the SPOT had resided in the same location for the last three years it was the last thing I suspected when I first encountered the problem. It was only after I changed the batteries in the SPOT that I had a clue to what the problem was. Obviously, I had already eliminated other devices that may cause the problem, cell phone, transponder, com radio, etc. After I put fresh batteries in the SPOT it started to occur more frequently, every five minutes, which is the refresh period for the SPOT. The SPOT is apparently sensitive to battery voltage, and while it still blinks properly, the signal strength diminishes with battery power. Maybe that’s why they tell you to use lithium batteries.
I went to the SPOT support page and on page 16,384 , it does warn against placing the SPOT less than 12 inches from a GPS. The sun shield in the 180 is aluminum, so one would believe it to provide some RF shielding and like I said, it had been coexisting with the 650 for three years without a problem. An Internet search only revealed one incident of a SPOT causing this problem. That was with a GTN-750, the big brother to my 650. I use the same SPOT device in my experimental SuperCub variant, but it resides up on the wing root, plus the avionics in that airplane are much simpler, transponder, comm radio and Garmin 560.
I recently had an ADS-B system installed in my Cessna 180. I installed a Garmin GTX-345 and connected it to my Garmin GNS-650.
During testing to meet the compliance requirements and get my $500 rebate I had a problem keeping the 650 from losing satellites. It only occurred in flight and it was intermittent. All the satellites would drop out and the 650 would then re-acquire in about 1 minute. I couldn’t pass the compliance test.
After several more flights, switching antennas, turning off various other devices, swapping out the 650 and replacing the 650’s antenna, I finally figured out what the problem was.
The culprit turned out to be my SPOT Gen3 locator.
The reason I didn’t think it was the SPOT was that it has caused no problems in the last 3 years that I have had it in the same location, on top of the panel’s sunshield. Apparently, the added 345 and associated wiring influenced the RF absorption from the SPOT that it blanked out the GPS signal to the 650 when the SPOT would transmit position or messaging information. Since the SPOT had resided in the same location for the last three years it was the last thing I suspected when I first encountered the problem. It was only after I changed the batteries in the SPOT that I had a clue to what the problem was. Obviously, I had already eliminated other devices that may cause the problem, cell phone, transponder, com radio, etc. After I put fresh batteries in the SPOT it started to occur more frequently, every five minutes, which is the refresh period for the SPOT. The SPOT is apparently sensitive to battery voltage, and while it still blinks properly, the signal strength diminishes with battery power. Maybe that’s why they tell you to use lithium batteries.
I went to the SPOT support page and on page 16,384 , it does warn against placing the SPOT less than 12 inches from a GPS. The sun shield in the 180 is aluminum, so one would believe it to provide some RF shielding and like I said, it had been coexisting with the 650 for three years without a problem. An Internet search only revealed one incident of a SPOT causing this problem. That was with a GTN-750, the big brother to my 650. I use the same SPOT device in my experimental SuperCub variant, but it resides up on the wing root, plus the avionics in that airplane are much simpler, transponder, comm radio and Garmin 560.