Heathkit SB aftermarket mic

Discussion in '"Boat Anchor" & Classic Equipment' started by N1WVQ, Apr 30, 2020.

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  1. N1WVQ

    N1WVQ Ham Member QRZ Page

    I have no microphone for my SB-100/102/110/401 rigs. I would like to get the Heil GM Vintage, which has an impedance of 30k ohms. In reading the material about the stock mic, the HDP-21A, its impedance is 100k ohms minimum. Would I be able to use a Heil with the SBs & just change the level, or is it more involved? Thanks!
     
  2. W9GB

    W9GB Ham Member QRZ Page

    56646E08-231D-4597-85BC-4416BE99DBC5.jpeg 6B174029-455D-4B64-B8DF-5EC087A8765F.jpeg
    The Heil GM Vintage uses a 4-pin XLR connector.
    You will have to DIY fabricate a proper cable for the Heathkit SB-series transmitter/transceiver.
    The proper microphone connector for Heathkit: Amphenol # 80MC2M
    EBB1EBD9-741D-4C7C-B6A2-8694EA799685.jpeg
    The 80MC2M is a 2-position Male Cable Plug with chrome-plated machined brass shell, threaded coupling and black phenolic dielectric.
    • 5/8" mounting hole
    • 1-11/32" Maximum thickness for lock nut type receptacle
    ==
    How to install/wire shown in MH-31A manual (below).


    As far as impedance difference (30K ohms versus 100K ohms), not significant in this usage (both Hi-Z).
    ===
    The GH-12 (cream, beige) and GH-12A (dark green, gray) was the Hand Microphone for Heathkit HW-101 and SB-series. OEM was Turner in Cedar Rapids, IA.
    https://www.rsp-italy.it/Electronics/Kits/_contents/Heathkit/Kits/Heathkit GH-12A hand-held microphone.pdf
    ==
    https://www.audioservicemanuals.com/pdf-download.php
    In the Heathkit microphone diagram, it MAY have a wiring error RED / BLK -- at far right --
    AND the bottom of switch wiring (handles PTT function).
    In receive, the MIC Element needs to be disabled / grounded.
    In transmit, the PTT + needs to be grounded (PTT - ) for radio to transmit and mic element connected to Audio + line.
     

    Attached Files:

    Last edited: Apr 30, 2020
    N2EY and K7TRF like this.
  3. W9GB

    W9GB Ham Member QRZ Page

    Heathkit HDP-21A Desktop Microphone
    Manual (4 pages, 1969, PDF attached below)

    Leeds Radio, 175 Walnut Street, Bronx, NY (Last of famous NYC Radio Row)
    Amphenol 80-MC2M male plug (has lock ring) $26.00
    http://leedsradio.com/parts-connectors.html

    Electro-Voice was the supplier for this microphone (638 model).
    CBEC1858-DDBC-4FA5-92AC-04F9FB5449B6.jpeg
     

    Attached Files:

  4. W5RKL

    W5RKL Ham Member QRZ Page

    The Heil GM Vintage microphone requires the Heil CC-1 cable 4 pin XLR adapter cable.

    I use one of the inexpensive PYLE PDMICR42R RED desk microphone with a floor stand. This
    microphone has a low impedance 3 pin XLR output so I use the SHURE A85F low impedance
    XLR to high impedance adapter. The Shure A85F adapter has a 1/4"mono output male plug.

    I found a 6 foot 1/4" female to 1/4" male mono cable that accepts the A85F adaptor's
    high 1/4" male plug output. The male plug plugs into a 1/4" mono socket mounted on
    a small metal box.

    I replaced the 2 pin mic socket on the HW-101 and SB-100 to a 1/4" Stereo socket.
    I made my own 3 wire (2 wires and a shield) cable that has audio, PTT, and ground.
    PTT is a N.O. (Normally Open) foot switch.

    The microphone cable from the box has a 1/4" Stereo plug with audio on the "TIP",
    PTT from the foot switch on the RING and ground for both mic and PTT on the
    SLEEVE. It works quite well. I use it on my HW-101, SB-100, and Heathkit Apache
    TX-1.

    The PYLE microphone has a lot of audio so if used, the MIC gain must be set so you
    don't overdrive the speech amp with normal speech.

    73
    Mike W5RKL
    https://www.w5rkl.com
     
    Last edited: May 1, 2020

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