KX 125 NAV/Comm Issue

Before I try to diagnose the problem myself I will put it out there for everyone. Should be a simple fix.
Since my first flight last July, the NAV portion of my KX125 has been giving a flag indication meaning that it is not receiving a VOR signal. The Comm side works great. I suspect it is the antenna or cable. I am using a Bob Archer antenna in the wingtip. I think my first step would be to eliminate the antenna by hooking up another VOR antenna to see if I get reception. My gut feeling is that the problem lies with the coax cable. Hopefully, the problem is not in the navcomm which cost plenty o' money new.

bsacks05 said:

Before I try to diagnose the problem myself I will put it out there for everyone. Should be a simple fix.
Since my first flight last July, the NAV portion of my KX125 has been giving a flag indication meaning that it is not receiving a VOR signal. The Comm side works great. I suspect it is the antenna or cable. I am using a Bob Archer antenna in the wingtip. I think my first step would be to eliminate the antenna by hooking up another VOR antenna to see if I get reception. My gut feeling is that the problem lies with the coax cable. Hopefully, the problem is not in the navcomm which cost plenty o' money new.

Click to expand...

I think you answered your own question. Start eliminating possibilities with trying a known good antenna.

Since my first flight last July, the NAV portion of my KX125 has been giving a flag indication meaning that it is not receiving a VOR signal. The Comm side works great. I suspect it is the antenna or cable. I am using a Bob Archer antenna in the wingtip.

Click to expand...

I too use the KX125 with the Archer NAV antenna. The combination works great and is a good value.

Before I was able to get everything in the KX125 to work properly, I had to revisit the wiring pinouts a couple of times. There are some jumpers between pins that must be in place for all the radio's features to work. Some of the jumpers are not obvious and you have to really dig into the schematic to find them. The jumpers are necessary when external stuff like other radios and CDI's aren't connected to the KX125..

If your radio worked correctly at one point then the NAV section died, this won't be your problem. But if the radio has never worked properly, give the connectors/schematic another careful look to make sure nothing was overlooked.

You will be very pleased with your radio/antenna combination once you get it sorted out.

I've been working on the same problem on a KX-125 installation that I wired for another builder.

We went thru the same things that you are contemplating and finally have narrowed it down to the VOR pigtail out of the back of the radio rack (at least as far as we know at this point). As soon as the weather warms we will pull the rack and checkout the rack.

The final test(s) was the put a temporary VOR antenna in the cockpit (RV-8A) and then to swap radios from a known good installation in another RV. The tests showed that the radio works fine in the other plane and the temp antenna would not raise a flag when direct connected to the VOR pigtail with either radio.

I do plan on checking the schematic again based on Sam's comment in his posting to make sure I didn't miss a jumper...

Deene Ogden
EAA Tech Counselor/Flight Advisor
RV-8QB underway