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How to add TE-32 encoder to IC-25H

Discussion in 'Radio Circuits, Repair & Performance' started by KB1IOE, Feb 21, 2009.

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  1. KB1IOE

    KB1IOE Ham Member QRZ Page


    Where do the 3 leads from my new Com Spec TE-32 tone encoder go on the PC Board on my icom IC-25H?

  2. W9GB

    W9GB Ham Member QRZ Page

    Steven -

    Hopefully you have the Service Manual for your Icom IC-25H VHF radio.
    Service manuals have photos and pictorial diagrams of inside layout of radio.
    You need to identify the R34 / R36 connection points inside this radio that is where the
    WHITE wire of the TE-32 goes (Yellow for SS-64 encoder).
    RED wire is for +12 VDC and BLACK wire is GND (Standard DC power wiring color usage), tie to power supply for radio.

    IF you have no workbench time / soldering experience --
    ASK FOR HELP (Elmers, Local club technical group, your local Motorola radio shop --
    who have installed thousands of these for LM radio since 1960s).

    TE-32 manual/brochure

    Com-Spec instructions for TE-32 to Icom IC-25A/E/H

    Last edited: Feb 22, 2009
  3. WD4CHP

    WD4CHP Ham Member QRZ Page


    I Installed a switch programable tone board in the HM 8 mic.

    I wired it to the same points the tone pad is connected.

    The switch on the mic turns it on when needed.

    The output of the board is low enough to prevent clipping.
  4. W9GB

    W9GB Ham Member QRZ Page

    Willis -

    While you report that this approach worked for your specific situation --
    Your stated alternative is not best practice -- not repeatable.

    This output generates the CTCSS encode tone. The most common place to connect this line is just prior to the modulation stage in the transmitter. Typical connections would be to the center of the deviation pot. to the varactor diode in the modulator circuit, or to the manufacturer’s suggested connection point. This connection point can vary from radio to radio.
    Do NOT connect the CTCSS Output to the microphone input as the microphone audio stages will distort and attenuate the CTCSS signal.
    Some radios actually have an audio filter to cutoff subaudible sound from microphone below 300 Hz !!

    Since the CTCSS Output on the SS-64 is low impedance, you may have to install a series resistor to reduce the loading effects of the CTCSS Output depending on the interface impedance. This is evident in the case of connecting to the center of a 100K deviation pot. In this case, a 100K series resistor will compensate for the impedance difference. In addition, a slight adjustment of the voice deviation may be required to compensate for the CTCSS Output circuit loading.

    The CTCSS Output Adjustment, P101, is the only adjustment required on the SS-64. This control sets the level of the CTCSS Output. The supplied CSI tuning tool should be used to make the adjustment on the SS-6.4 PCB. To adjust the CTCSS Output level to the correct deviation, key the PU switch on the microphone and while watching a deviation scope tuned to the transmit output frequency, carefully adjust the CTCSS Output Adjustment. The deviation level of the CTCSS Output should be set to 0.75 kHZ (750 Hz). A deviation scope on a service monitor is best for adjusting the CTCSS deviation. The CTCSS waveform on the scope will appear as a sine wave.
    IF the CTCSS signal appears distorted (scope), this indicates that the interface connection is incorrect, and must be changed to a more suitable location.

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