Originally Posted by Slane
I'm not at all comfortable at reading electrical diagrams and so maybe the answer to my question is there, I just don't know how to read it. Here's the question: When I press my mic button (PTT), my EGT displays start doing the pogo-stick imitation and jump up and down. This is true for either the pilot or co-pilot. When the PTT is released, the jumping stops and the EGTs read normally. I have the pre-08-25-11 wiring harness for the Skyview.
I've needed to replace both EGT probes some time ago and have experienced good performance since.
When I study the electrical schematic, I see no reference to EGT wiring and could use the help of this group to know where to go next.
Thanks in advance.
Sounds like RF from the transmitter is getting into the wiring. Often this is caused by bad antenna SWR. Bad SWR can cause the coax cable between your radio and antenna to radiate RF power into nearby wiring, potentially causing all kinds of weird problems, and it's also not good for your radio.
I had a similar problem in my RV-7A with the same symptoms as yours, and it turned out to be a badly installed BNC connector at the antenna end of the coax cable. The center conductor was shorted to the braid on the antenna end. Installing a new connector fixed the issue.
Others have had bad SWR because of a badly grounded antenna.
Just making sure there's continuity from the center pin at one end to the center pin at the other, with no connection between the center pin and the outer shell can tell you a lot about whether the coax cable is bad. And inspect the center pins to see if they're as far forward as they should be. Also test continuity while flexing the cable at the connectors to see if you have a short/open that only happens when the cable is in a certain position.
One other diagnostic is to see if transmitting on a handheld radio nearby causes the same problem. You might just have electronics that are overly sensitive to RF. In this case a talk with the manufacturer might get you resolution.