Calgary Amateur Radio Association

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DTMF Tone Generator Project

  • 23 Dec 2020 8:25 PM
    Reply # 9449384 on 9441547

    Hi Ken:

    Sure let's do the photos and schematic.  Ya to access the tones programmed into the machine is definitely awkward.  And the number you can program in is limited and you cannot annotate them.  So a typed and laminated list of codes and a keypad for me is the simplest way.  I'm going to pick up one of those electronic circuit project blocks that I can just plug leads into until I find the right combo. My email is  Thanks again and Merry Christmas!

  • 23 Dec 2020 3:55 PM
    Reply # 9449035 on 9441547
    Ken Oelke (Administrator)

    Hello Mike,

    It has been about 35 years since I used this, and I can not remember where I got the technical information to wire this up. I can take some photos and draw a schematic of the mod and send to you.

    Looking at the IC 7100 manual, and doing some reading on the Internet, have you checked out pages 1-11 and 1-12? From what I read, you can program DTMF tones into memory, but it is a bit of a pain? And sure, you can borrow my key pad, but maybe pictures and a schematic will get you going?


  • 22 Dec 2020 5:53 PM
    Reply # 9447251 on 9441547

    Hi Ken:  Thank you very much for your kind offer!  I already have the phone keypad so perhaps I  can just borrow yours to see how it is wired?  I kind of like the idea of building this project as I need some incentive to get more involved in radio.  

    I have the HM-151 mic which I bought for that very reason but sadly found out after the fact that it does not do DTMF tones.  The buttons are for many other things except that.  I went through the manual with a fine tooth comb and several online forums which confirmed it.  The thought of being able to use another make of mic never crossed my mind.

  • 22 Dec 2020 8:08 AM
    Reply # 9446144 on 9441547
    Ken Oelke (Administrator)

    Okay are quite welcome to have mine for free, but Icom does make a DTMF mic for the Icom IC 7100. It is a HM151, but it appears to be very expensive. Maybe an aftermarket one will work, for less money? I can send a photo, if you are interested?

    Ken Oelke, VE6AFO

  • 21 Dec 2020 11:27 PM
    Reply # 9445344 on 9441547

    Hi Ken.

    Thank you for the info.  My plan is/was to use the keypad tones to open and close the FARS and SARA IRLP node repeaters.  Right now I am using a DTMF tone generator app on my phone which is much faster than accessing the DTMF tones I have programmed into my IC7100. As well Icom does not make a mic with this capability like other brands.

  • 20 Dec 2020 6:54 PM
    Reply # 9443108 on 9441547
    Ken Oelke (Administrator)


    I understand what you are trying to do, but if your idea is to use the DTMF telephone pad to generate, say the CTCSS tone to open up a repeater I.e. 110.9 Hz for CARA repeater VE6RYC, this will not generate the single tone you need. The telephone DTMF (dual tone multi frequency) pad generates two tones for each pad number. Google DTMF tones for the complete chart of dual tones for each pad number.

    Your idea could be used to generate the required tones to access an auto patch from the mobile, but at this time there are no auto patches on any of the Calgary repeaters. If you do decide to do this, you do not need 48 volts. This can be done with 12 volts only for the on board tansistors. I did this many years ago, in fact, I still have my old DTMF telephone pad mounted in an old ladies shaving case with a curly cord coming out of it, hi.   

  • 19 Dec 2020 8:31 PM
    Message # 9441547

    I have a project in mind to take the salvaged keypad and DTMF tone generator circuit from a 1980 telephone and wire it in such a way that I can plug it into the aux. mic port of my radio and use it to open and close repeaters. As telephones use 48VDC and radios 12VDC, a step-up transformer would also be required for the power from the mic cord to the keypad.  If anyone has done this or has some helpful hints, I would be most appreciative.  VE6MJY

    Last modified: 19 Dec 2020 10:40 PM | Mike Yakey
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