The definitive Van's Aircraft support community! Buying, building or flying an RV? Join our exclusive family of mentors and enthusiasts!
Rv detective 1. Electrical gremlins 0.Looks like the culprit has been identified!
Didn’t have time to panel dive to unplug the GRT GPS antenna, but when I shielded it with some aluminum foil the problem went away - then returned with a vengeance when I removed the foil.
iCloud Photos - Apple iCloud
View, organize, and share photos and videos with iCloud Photos on the web. Changes will sync across your devices with iCloud.share.icloud.com
That is my read. I believe even garmin has had this issue. I don't see it as a Quality issue, just bad luck. Though I would not just pick the cheapest on the web to replace it. My GRT was shipped with a branded ant, not off shore junk.I could also be overthinking this in response to a unicorn problem that won’t likely happen again.
Yes, my sleuthing indicated that Garmin definitely had this issue. Apparently early GA 35s would occasionally be damaged during installation (the bottom plate would crack?) and they would then become quite effective jammers.
No no no. Do not pick a random antenna. Unlike, say, a glide slope antenna (where a coat hangar probably works) these GPS antennas are looking at incredibly weak signals. The whole reason they get dc power is so a pre-amp can be built into the antenna, reducing noise problems from unwanted pickup in the coax. Know of any other system that goes to these extremes? Your antenna not only has to have the right plug, and use the same voltage, but the gain must be matched to the (GRT in this case) receiver. Enough for a good signal, but not so much that overload and stray signal rejection becomes an issue. These things are so finicky that my Garmin 430W specifies a minimum coax length or other signal loss thing (because the pre-amp gain turned out to be a tad high.) So: look not only for the required power and plug type, but also similar gain characteristics, to the OEM antenna. Honestly, for $25, I’d just buy the identical replacement from GRT. Do remember that these preamps are solid state devices which have some sensitivity to heat. Use a sunscreen if parked in the sun, and make sure no heating vents direct hot air at it.Anyone have ideas for a replacement antenna?
It’s got to have an MCX plug and run on 3 to 5 volts. This seems to describe an ocean of cheap GPS antennas, many of which are available for under $10. GRT wants $25 for theirs, and since I’ve had one bad experience with whatever they’re using, I was thinking I’d source my own.
Is there a known high-quality manufacturer of these gadgets? Failing that, I’m literally pondering just finding the most expensive one available, possibly intended for marine use, and hoping that equates to quality.
I could also be overthinking this in response to a unicorn problem that won’t likely happen again.
Even the best LNAs inevitably add noise and degrade the signal from the antenna, while they attempt to compensate for the loss in the coax. For short cable runs it's possible that a passive antenna will work just fine. If the passive antenna works with GRT that would be my choice. Some GPS receivers measure DC resistance to confirm the active antenna is plugged in, but they can be tricked sometimes by adding a resistor between the shield and inner conductor. May worth asking GRT if a passive antenna is acceptable. If the interference continues it could be the GRT unit itself is transmitting. just 2 cents worth
Jamming civilian GPS on a small scale seems almost trivial. It happens all the time by accident and on purpose as we see in many reports. https://www.faa.gov/about/office_or...GNSS/GPS_GNSS_Interference_Resource_Guide.pdf
It can’t be that hard to do if I accomplished it.
Possibly! My theory is that the antenna was damaged by heat (it’s black and lived on my black glareshield right under the plexi). Who knows.
