All,
I am chasing some gremlins in my wiring. When I transmit my EFISes show varying degrees of pitch and roll changes. Here is my setup:
- Dual GRT (one HX and one HS)
- COM 1 - 430W
- COM 2 - SL40
- Com antennas - Rami bent whip on belly near centerline (one near wing spar carry-through and one just aft of the rear passenger seat)
- AHRS just aft of rear baggage compartment and just forward from elevator bellcrank
- Both antennas fed with RG400 running down left side of fuse
- DU/AHRS wiring down right side of fuse
- Magnetomer wiring running up right side (with AHRS wires) to just before the main wing spar and then out right side of fuse. The cable exiting the fuse is about 12 feet long.
- Everything is in my garage (not a metal hangar)
- GRT's have not been "calibrated"
Observations:
When I transmit I get varying degrees of pitch and roll changes on DU's. The changes on the two DU's are always in the same direction. However, the magnitude of the change on each DU can vary. The overall problem varies a little with transmit frequency. But, it seems much more sensitive to magnetometer and magnetometer wiring location. When the wiring drapes down below the fuse, the problem is worse. When I place the magnetometer on top of the fuse back at the tail and route the wire along the top of the fuse, the problem is minimized.
Side note: I originally had RG58 going to the COM2 antenna. Thinking this could be the problem I purchased some RG400 and ran it direct between the transmitter and the antenna (i.e. didn't physically remove the RG58). When I switch between the RG400 and the installed RG58, I see no difference in the symptoms.
Hypothesis:
RF energy from the COM antennas is coupling into the magnetometer wiring and causing the pitch/roll changes.
Questions:
Should I not worry about this now and wait until the wings are on and such? Does the wing provide some shielding for the magnetomer and associated wiring? I'd much prefer to clear this up now when the access is better.
I'll be contacting GRT on Monday, but thought I'd check here and see if anyone else had any experience with this.
Thanks,
I am chasing some gremlins in my wiring. When I transmit my EFISes show varying degrees of pitch and roll changes. Here is my setup:
- Dual GRT (one HX and one HS)
- COM 1 - 430W
- COM 2 - SL40
- Com antennas - Rami bent whip on belly near centerline (one near wing spar carry-through and one just aft of the rear passenger seat)
- AHRS just aft of rear baggage compartment and just forward from elevator bellcrank
- Both antennas fed with RG400 running down left side of fuse
- DU/AHRS wiring down right side of fuse
- Magnetomer wiring running up right side (with AHRS wires) to just before the main wing spar and then out right side of fuse. The cable exiting the fuse is about 12 feet long.
- Everything is in my garage (not a metal hangar)
- GRT's have not been "calibrated"
Observations:
When I transmit I get varying degrees of pitch and roll changes on DU's. The changes on the two DU's are always in the same direction. However, the magnitude of the change on each DU can vary. The overall problem varies a little with transmit frequency. But, it seems much more sensitive to magnetometer and magnetometer wiring location. When the wiring drapes down below the fuse, the problem is worse. When I place the magnetometer on top of the fuse back at the tail and route the wire along the top of the fuse, the problem is minimized.
Side note: I originally had RG58 going to the COM2 antenna. Thinking this could be the problem I purchased some RG400 and ran it direct between the transmitter and the antenna (i.e. didn't physically remove the RG58). When I switch between the RG400 and the installed RG58, I see no difference in the symptoms.
Hypothesis:
RF energy from the COM antennas is coupling into the magnetometer wiring and causing the pitch/roll changes.
Questions:
Should I not worry about this now and wait until the wings are on and such? Does the wing provide some shielding for the magnetomer and associated wiring? I'd much prefer to clear this up now when the access is better.
I'll be contacting GRT on Monday, but thought I'd check here and see if anyone else had any experience with this.
Thanks,