Weak NAV 122

[MBDiagMan]

The GNC420 I put in the 140 is wonderful, but in the installation process, we removed a NAV 121 that was NAV2. This left an open output on the antenna splitter. The NAV122 has always worked wonderfully, but is now weak. It won’t pickup the local VOR when at the test location on the airport. It picks it up once I’m a thousand feet or so up, but tests 6 degrees off. The audio from it is nothing but noise.

Could it be that disconnecting the VOR2 antenna from the splitter is causing an impedance mismatch?

 

[Doug Reid]

No..but you might have a poor connection on your coax.

 

[MBDiagMan]

Yes, that’s also a possibility, but other than removing the other NARCO, the coaxes were untouched at the recent 420 installation.

When I was a radar repairman in the Army, I found and fixed a lot of problems by wiggling on coax cables and connections and then repairing them. They were easy to get at though, without being under the panel standing on my head.

 

[GeorgeC]

Dumb question, if you have a splitter with nothing attached to one leg, does it need a terminator?

 

[MBDiagMan]

Good point and that relates to my impedance mismatch question. In fact the splitter was there because there were two NAV’s. Do I no even need it at all? I think I do because it allows one antenna to feed the VOR and the glide slope connections on the NAV.

 

[GeorgeC]

I'm not an avionics guy, but sounds like you can ditch the splitter since you only have one nav, but you'd still need a diplexer for the loc/gs. @Jesse Saint?