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I just got a used Kenwood tm241a. It was working fine on my friends antenna until I took it home and hooked it up to a used Larsen nla-mm antenna I bought at a ham-fest.

It seemed to work fine on that antenna for a bit until I was hearing a weird hum out of the speaker on the higher edge of the 2 meter band on 50 watts. My Baofeng handheld picked up all of this spurious emissions on any frequency I tuned to.

I then decided to test it one more time with a friend on a repeater, and it transmitted this weird one-tone beep when I keyed up the microphone, and didn't stop when I unkeyed it, the transmitting stopped only when I unplugged the microphone, rebooted the radio, and plugged the mic back in. The beep pitch changed by pressing different buttons on the mic, but wasn't the familiar two-tone DTMF, and was a one-tone beeping.

Is this radio fried, or is there a way to fix it? Does the DTMF mic possibly have a problem, or is it most likely an internal radio issue? The day I finally got a nice 50 watt radio for my net control, and the courage classic bike race, It burned out. I cant see a nice kenwood die, and as a cheapo high school student, cant afford a new radio :(

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  • $\begingroup$ Did you buy it at a hamfest? Did the seller say "It worked the last time I turned it on"? Typically this means the seller stopped turning it on, because it's broken :) $\endgroup$ – Phil Frost - W8II Feb 12 '14 at 19:13
  • $\begingroup$ it transmitted this weird one-tone beep This sound to me like it might be some sort of diagnostic mechanism. Did you try looking up a service manual for the radio? It could be listed there. $\endgroup$ – AndrejaKo Feb 12 '14 at 19:37
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    $\begingroup$ Perhaps also relevant: DTMF signals with two tones, one for the row, and one for the column of the button pressed. On older telephones, if you pressed two buttons in the same row or same column, you'd get the single tone for that row or column. Some DTMF equipment retains this capability. Perhaps it's an indication that one of the buttons on the mic is stuck? $\endgroup$ – Phil Frost - W8II Feb 12 '14 at 21:44
  • $\begingroup$ The DTMF worked perfectly first, and the radio worked perfectly on my friends antenna until I hooked it up to mine $\endgroup$ – Skyler 440 Feb 13 '14 at 0:19
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    $\begingroup$ Here is the service manual repeater-builder.com/kenwood/pdfs/tm-241ae-svc-man.pdf $\endgroup$ – KD5QLN Mar 2 '14 at 23:36
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I figured it out:

  • For the weird beeping, it was just a bad mike, and I had to replace that.
  • For the spurious transmissions, I should've specified I was on a SLA battery, and the battery was running low
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