Kenwood: Kenwood TM-742 weak receive

[WX5812]

I have a Kenwood tm-742a that I keep in the mobile. I've noticed here lately that the receive on the 440 side has gotten weak (repeaters that should be full scale are half or less) has anyone experienced this problem or have a solution? I can get another 440 module pretty reasonable but wanted to see if there was anything I could do first.

 

[WA0CBW]

Have you checked your antenna for corrosion or water contamination?
BB

 

[WX5812]

I have not, but it is a tri band antenna and the 2 meters and 6 meters are working fine thats the only reason I have not checked that. could it be possible that could be the issue?

 

[WA0CBW]

I would check the connections to your tri-plexer. I have had pl259's work their way loose over time.
BB

 

[cmdrwill]

Seen a lot of radios like yours that have damaged RF frontend transistors damaged by high VSWR. Time to accualy measure the receiver's sensitivity with a service monitor. And yes just one range may be barfed.

 

[WX5812]

Thank you I will defiantly check the swr. Is there anyway to fix the recieve side of the 440mhz unit if it’s damaged?

 

[cmdrwill]

Some we replace the FE transistor, but not sure on the older Kwoodies.

 

[AK9R]

Is there anyway to fix the recieve side of the 440mhz unit if it’s damaged?

If it's purely an RF problem and not anything to do with the firmware or components in the control head, it may be easier to just swap out the module. The TM-742 was a modular radio. Out of the box, the radio consisted of a 2m module, a 440 module, a control head, and covers for the modules. There were other modules available for 10m, 6m, 220 MHz, and 1.2 GHz. The TM-642 was the same as a 742 except that it came with the 2m and 220 MHz modules. The TM-942 came with 2m, 440 MHz, and 1.2 GHz modules.

So, if you have a problem with the 440 MHz module, you should be able to find a replacement on the used market. On eBay, look for w5cia selling parts for these radios. He parts out the TM-x41 and TM-x42 line and has a large inventory.