Poor radio performance

[mikejr718]

I have a tkm mx11 as the comm 2 in my 1975 Mooney m20c ranger.  The radio seems to have limited range and usually fails to transmit sometimes after warmed up. Comm 1 is a narco mk12d+ that works surprisingly well for being a narco. Standing back looking at the plane a few days ago it looked like the finish on the rear antenna did not match the rest of the plane.  I have the stock 7 antennas. The cork gasket at the base of the radio looked dried up and shriveled so I thought I would remove the antenna and see if it appeared corroded, damaged etc.  It was attached with three painted screws  and one ground type screw with two star washers on it.  The gasket was keeping the  entire base of the antenna from contacting the aircraft and underneath the antenna was completely painted.  I also have continuity from the center pin of the antenna to the metal base of the antenna.  I confirmed the rear antenna is connected to comm2.  Can I assume that this installation of this antenna could be part of the problem and the antenna itself may be bad based on the continuity from the center antenna conductor and the antenna base?

Edited January 24, 2018 by mikejr718

[takair]

That could be a contributor.  At a minimum, the screws need to have good contact.  With that particular antenna, you can get a good ground plane by cleaning paint so the rivnuts in the antenna make metal to metal.  It the antenna got moisture in it, it may need replacing. Since you have it off, clean things up, get metal to metal around the screws,. Alodine helps prevent corrosion.  Seal the perimeter and try it out.  Avionics shop can do more sophisticated things like power check.  

[StevenL757]

I agree.  Clean, clean, clean.  Cleaning can be your best friend; and in some cases, your cheapest insurance.  Never discount the importance of mineral spirits and paper towels.

Steve

[carusoam]

Welcome aboard, Mike!

 

Cleaning all the contacts is a good idea...

can you swap the antenna wires going to the antennae for com1 & com2?

This would prove the antenna is working or not.

Another thing that can be tried... get another radio to swap for the one not working.

Is the TKM an updated BK radio? A radio shop may be your friend for this...

The connections can be oxidized at the slide in radio as well...

Could be connections.... could be old analog radio parts....

PP thoughts only, not a radio tech...

Best regards,

-a-

[mikejr718]

Is there supposed to be continuity between the antenna wire and the metal parts of the antenna that the screws go into?

[tigers2007]

Coat the actual connections with Deoxit. I use the D100 in the little red bottle with the needle applicator. Expensive but works miracles.


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[jaylw314]

13 hours ago, mikejr718 said:

Is there supposed to be continuity between the antenna wire and the metal parts of the antenna that the screws go into?

I don't believe so, the screws and base should be in contact with ground (the airframe via the grounding screw).  Where are you checking the antenna wire and base?

The base should be completely isolated from the airframe by the gasket to prevent dissimilar metal corrosion, but they both should be connected by the grounding screw (easier to replace a corroded screw/rivnut than the antenna or airframe).

[mikejr718]

Wanted to update this thread. Tracked down problem to an antenna access port installed between the radio and antenna.  Removed it and things improved drastically.  I looks somewhat home made and allowed some one to hook up a handheld radio and use the antenna associated with the mx11. It was mounted in the panel near the radio.  After removing it had to open it up to see the insides

Edited May 17, 2018 by mikejr718

[EricJ]

Looks like somebody tried to duplicate a King KX99 antenna adapter.  

[Marauder]

Looks like somebody tried to duplicate a King KX99 antenna adapter.  

And did poorly at it.


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