No COS line in Kenwood TM531

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This topic contains 6 replies, has 3 voices, and was last updated by  Aaron, N3MBH 1 month, 2 weeks ago.

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  • #2944

    Hi,

    Maybe anyone can help me here.
    I try to build an 23cm Repeater with two old Kenwood TM531 TRX and the PI-Repeater-1X board.
    Now i have the problem with the COS line. There is no COS connection possible on the front MIC connector.
    What can i do now?
    Anyone know where i can get this Signal out from the rig?

    Thank you for help!
    73s Klaus, OE4KMU

    #2947

    Aaron, N3MBH
    Forum Administrator

    I am not familiar with this radio, but if it doesn’t have and external pin for this then you will need to modify the radio to add a control pin/line. Does the radio have an RX LED that you can pull COS from?

    73,
    Aaron – N3MBH

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    #2949

    Hi Aaron,

    Thanks for your reply and sorry for my delay. Yes i have a second radio (IC-1200) this Radio have a TX/RX LED on the front Display. Where can i get out now the correct Signal?
    Please have patient with me, i‘am not so good in the electronic business…

    73 Klaus, OE4KMU

    #2950

    Dan Loranger
    Forum Moderator

    Hi Klaus,

    This is Dan from ICS, I have read up on the TM-641/741 service manual (closest I could locate that was legible, http://www.repeater-builder.com/kenwood/pdfs/tm-641-741-svc-man.pdf, see page 23 for the 3 sentence description of squelch volume input) and best I can tell, the way squelch is done on the radio does not lend itself to being able to extract the signal from the radio easily.

    The best I think you can do is to tap the voltage output of the squelch circuit (I didn’t get into this level of detail schematically) and putting that into a comparitor circuit with a potentiometer to adjust the threshold and use the output of the comparitor circuit as your squelch. Of course this will not nicely match the software version of the squelch circuit so the software would have the be set the software version to a minimum level and then use the external built circuit as the control for the repeater.

    In this particular instance, you may be best suited to using VOX or see if you can find a ham with a radio that exposes the COS circuit that you can make a reasonable trade with.

    #2951

    Dan Loranger
    Forum Moderator

    Hi Klaus,

    If your IC-1200 has a COS LED you can get access to, that would be far easier,I suggest to have someone who is familiar with electronics and soldering help you to add a wire to the LED (Be sure to get the signal that has at least 3V-5V driving it (you may need the current limiting resistor instead of the LED) to use as the COS signal on a controller.

    This will be your best approach for getting the squelch control signal from your two radio options.

    Good Luck

    Dan

    #2952

    Hi Dan and Aaron,

    Thank You very much for your help. I got the Cos Signal out from the Squelch LED how you wrote. Now the repeater works fine.
    Greetings from Austria.

    73s Klaus, OE4KMU

    #2955

    Aaron, N3MBH
    Forum Administrator

    Glad to hear Klaus. Glad it worked for you!

    73,
    Aaron – N3MBH

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