Garage Guy
Well Known Member
Not sure whether to post this under GPS or COMM; it is the unholy marriage of the two...
Some background is here on this thread http://www.vansairforce.com/community/showthread.php?t=36776, but basically, where I am so far:
Our KX-155 comm interferes with GPS in our RV-6. When transmitting on frequencies near 121.175 MHz, which has its 13th harmonic pretty much on the main GPS satellite carrier frequency, it takes out satellite reception both in the panel mount GX60 and the GPS 496 handheld. The effect is not subtle.
I have put a GPS notch filter in the comm antenna line from the KX-155; no change. I have replaced the 12" coax pigtail on the KX-155 with a female BNC connector, to put the notch filter directly on the back of the KX-155; no change. I have put two notch filters in series (I have a collection of these now); no change. Someone said a ELT in the airplane can be a problem; I disconnected the ELT antenna, no change. I have swapped comm antennas (the GX60 comm doesn't have this problem); no change.
I don't know, but I think at this point that it is something other than the comm antenna that is radiating the interfering energy from the KX-155. Some GPS install manual (maybe the GNC300XL... I have looked through all of these I can find) says if a notch filter doesn't help, then shield the whole cable bundle coming from the comm tray connectors.
So,my questions at this point: What is the best way to shield an existing cable bundle? Or, any other ideas?!
Thanks,
--Paul
Some background is here on this thread http://www.vansairforce.com/community/showthread.php?t=36776, but basically, where I am so far:
Our KX-155 comm interferes with GPS in our RV-6. When transmitting on frequencies near 121.175 MHz, which has its 13th harmonic pretty much on the main GPS satellite carrier frequency, it takes out satellite reception both in the panel mount GX60 and the GPS 496 handheld. The effect is not subtle.
I have put a GPS notch filter in the comm antenna line from the KX-155; no change. I have replaced the 12" coax pigtail on the KX-155 with a female BNC connector, to put the notch filter directly on the back of the KX-155; no change. I have put two notch filters in series (I have a collection of these now); no change. Someone said a ELT in the airplane can be a problem; I disconnected the ELT antenna, no change. I have swapped comm antennas (the GX60 comm doesn't have this problem); no change.
I don't know, but I think at this point that it is something other than the comm antenna that is radiating the interfering energy from the KX-155. Some GPS install manual (maybe the GNC300XL... I have looked through all of these I can find) says if a notch filter doesn't help, then shield the whole cable bundle coming from the comm tray connectors.
So,my questions at this point: What is the best way to shield an existing cable bundle? Or, any other ideas?!
Thanks,
--Paul
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