MTR5B interrupts with band randomly

Home Forums QRP Transceivers MTR5B interrupts with band randomly

Viewing 5 posts - 1 through 5 (of 5 total)
  • Author
  • #3262

    I received my MTR5B yesterday as a wonderful early birthday gift from my wife, KD9BAU! When I hooked up to my home inverted vee with a soft 9 Volt battery and tuned to 40 meters, the first station I copied on 7026.4 was BY4K calling CQ! Unfortunately my barely 1 Watt didn’t reel him in for some reason. I have been having fun playing with it and have made a couple of contacts.

    The problem that I am trying to figure out is that, when I am in straight key mode (SKCC), it randomly interrupts my sending with the band info. I have not seen this happen in automatic mode at all, so far.
    I tried the following with no improvement:
    1. A new 9 Volt battery and then a 12 Volt gel cell.
    2. I added a ferrite choke to the key cable.
    3. I tried a different straight key with a much shorter cable.
    4. I switched the antenna to a dummy load.
    5. Straight key mode with my paddles.

    I am running out of things to try. Any thoughts? I do use straight key mode fairly often as I participate in SKCC.

    73 K9LJB


    Try removing the the internal battery and reinserting it. That may cure it. Be sure also you are not in the beacon mode.


    1 watt seems a little low for 9 volts. IIRC output power should be around 2.5 watts. Have you checked-out your -5B with an accurate power meter? I have never tried my -5B with a 9 volt battery. I use an AGM at 11.6 volts. I put a couple of silicon diodes in series with the B+ side to drop the voltage from about 13 volts closer to 12 volts or slightly lower.


    Hi Roger. Sent you an email to your k9ljb email address. I have the same problem. Mine started new out of the box, even sent it back and they sent me another new unit. New unit had the same problem, same attempts at fixing. Details in the email.

    The folks at LNR were very helpful and receptive, but so far no explanation. Tried the same things; battery out, filters, key changes, cables, on and on. Works great with keyer, but since I am a straight key guy, the keyer is just dead weight for me.

    Hope they figure it out. I suspect a lot more guys might have the same problem, but don’t know it because they might not be on the straight key as much.


    Jim, KG4IKQ


    Hi Roger,
    I have the same issue. It is the same issue that I had with my PFR-3. I believe that noise is getting into the BANDSEL and the microcontroller is detecting the voltage level as it moves outside the region set by the switches. The microcontroller then thinks that the momentary change in voltage was a band switch. C1 does not seem to be sufficient to keep out that noise.
    It would be nice if a software low pass filter could be added to the code. Even a simple averaging filter could help minimize the noise pulses.
    I like to do SKCC and yet this issue makes things difficult.
    72, JP, K8AG

Viewing 5 posts - 1 through 5 (of 5 total)
  • You must be logged in to reply to this topic.