D-180, Disappearing data when I key mic

[Speeddog8]

I've got 60 hrs or so on my D180 installed in a Glasair. Its worked great from the get go, but the other day, I noticed that when I key the mic, I see the graphical reading for EGT and CHT's slowly begin to reduce to nothing. As soon as I release the mic, the engine monitor goes back to normal operation. I think I recall that the problem didn't occur on all com frequencies. RF? I did recently move some of the wiring around within the fuselage (mostly to secure it better with ty-wraps. I didn't change any wiring though. Just moved it around a bit and tied it off to clear the elevator bellcrank and autopilot servo better.

Any Ideas?

Chad

 

[jakej]

Chad

Do you have 2 radios in the Glasair ? I've been chasing a similar problem but worse - each time I PTT 'warnings' come on (including audio) and CHT/EGTs show - 99C at times.

I too thought it was a radio frequency issue, tried btm/mid/top end of them but similar problems however when I tried #2 radio it all worked ok using the same tests. It appears the problem is an RF issue but as the antennas were already fitted to my customers Glasair I'll have to do an SWR check.

I'll advise further - please let us know how yours works out.

Jake J

Glasair IIS FT in OZ.

I'd suggest the RF is causing your problems

 

[Speeddog8]

Jake,
Better late than never,,, right? I never did "find" my problem, but the problem seems to have gone away for the most part. Occasionally, I'll key the mike and my TruTrak autopilot will pitch up or down slightly. Doesn't seem to do it all the time, but the Dynon EGT and CHT issue previously described has gone away. I only have one radio, but I added ADSB at some point. The antenna's associated with the ADSB have caused me a host of other gremlins from time to time. Mostly associated with "stuck squelch" on certain frequencies. I"m still chasing that one down.... but it rarely causes a problem. Chad- Glasair Super II-S FT

 

[sstearns2]

I had the same problem with my Trutrak A/P pitching up or down when I keyed the mike.  It seemed to me that the pitch servo would just shut down when the mike was keyed. 

The solution for me was to install an RF filter adaptor on the D-sub connector to the A/P computer. 

http://www.ebay.com/itm/Spectrum-Control-56-735-003-LI-Conn-Filtered-D-Sub-Adapter-37-PIN-SKT-POS-ST-1P-/191551032026?hash=item2c9954cada:g:vdcAAOSw34FVHDvV

Scott

 

[Robski]

I noticed that when I key the mic, I see the graphical reading for EGT and CHT's slowly begin to reduce to nothing.

Standard response to this is to change the Radio coax cable from RG58 to RG400. Expensive, but very often clears the problem.

About to do this when I change the RV's radio for an 8.33 spacing one as I sometimes get shock-cooling alarms off my D120 when I transmit.