TKM MX300 Issue

[Dbarbee]

I recently bought a used TKM MX300 to replace the original ARC RT328T in my Cardinal and the COM reception seems really weak and I wanted to see if anyone had any suggestions or similar experience.

By the time I'm 20-25 nm from the airport the ATIS and departure control are almost unreadable and by 30 nm they're completely unreadable. Reception and transmission on the ground are clear and strong but I haven't checked the transmission in the air yet. On the ground I'm also able to pick up a local VOR that's about 14 nm away. The COM on the original RT328T wasn't crystal clear in the air but it was much stronger at those distances and consistently readable 50+ nm from the airport. I tried swapping the MX300 with an identical model borrowed from a friend and it was much clearer, leading me to believe the problem is in the radio and not the airplane. (i.e. tray or antenna) The reception on the GNS430w mounted directly above the MX300 is always good.

According to the seller the radio was bought new and in service for about 1 year before being replaced by a G430. After the radio was removed it sat on a shelf for 10-11 years before I bought it.

Before I contact TKM or Bevan Rabell I wanted to get an idea what could cause weak reception and what the common failure modes are for these radios.

Any thoughts?

 

[SLarge78]

I recently bought a used TKM MX300 to replace the original ARC RT328T in my Cardinal and the COM reception seems really weak and I wanted to see if anyone had any suggestions or similar experience.

By the time I'm 20-25 nm from the airport the ATIS and departure control are almost unreadable and by 30 nm they're completely unreadable. Reception and transmission on the ground are clear and strong but I haven't checked the transmission in the air yet. On the ground I'm also able to pick up a local VOR that's about 14 nm away. The COM on the original RT328T wasn't crystal clear in the air but it was much stronger at those distances and consistently readable 50+ nm from the airport. I tried swapping the MX300 with an identical model borrowed from a friend and it was much clearer, leading me to believe the problem is in the radio and not the airplane. (i.e. tray or antenna) The reception on the GNS430w mounted directly above the MX300 is always good.

According to the seller the radio was bought new and in service for about 1 year before being replaced by a G430. After the radio was removed it sat on a shelf for 10-11 years before I bought it.

Before I contact TKM or Bevan Rabell I wanted to get an idea what could cause weak reception and what the common failure modes are for these radios.

Any thoughts?

Hi Daniel,
I have the same problem with my #1 TKM MX300. Just purchased the plane last month (1976 Cessna 177B) and I’m anxious to get it fixed. Were you able to resolve this issue?

Thanks,
Shannon

 

[Dbarbee]

Hi Daniel,
I have the same problem with my #1 TKM MX300. Just purchased the plane last month (1976 Cessna 177B) and I’m anxious to get it fixed. Were you able to resolve this issue?

Thanks,
Shannon

I didn’t get it completely resolved but it was good enough to use for my COM2 to pick up WX or monitor a second frequency. I used my COM1 (GNS430) for all of my transmitting.

I ended up taking it up to Bevan Rabell in Wichita so they could bench test it but they couldn’t find any issues. They did give it a good cleaning though and it seemed to do a little better. How far I could receive with it depended a lot on my altitude and the strength of the transmitter I was trying to listen to.

Incidentally, I also had it in a 1976 177B