Radio Shack HTX-10 Repeater PL/CTCSS Tone

Discussion in 'General Technical Questions and Answers' started by N1BCG, May 17, 2019.

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  1. N1BCG

    N1BCG Ham Member QRZ Page

    I recently acquired a 1997 vintage Radio Shack HTX-10 transceiver. It features all-mode operation on 10 meters and has received very positive reviews. However, there seems to be a lot of confusion over the PL/CTCSS tone generation function and adding to the mystery is that it's not even mentioned in the manual:

    Despite this, it is possible to activate an 88.5Hz tone by pressing the Function button and LCR/4 (one of six multi-function buttons). Supporting this, the display shows "RPT" when this is done and I have measured an 88.5 Hz tone on the carrier. It can be turned on and off just as easily as if it were a normal function despite there being NO mention of it in the manual, although this IS mentioned on pages 8 and 9 in the Magnum 257 manual which is a nearly identical transceiver:

    Unfortunately, every copy of the HTX-10 service manual has a very poor quality schematic, but a nearly identical rig is the AE485S. That schematic can be seen in higher resolution here:

    As far as I can tell, the Sanyo LC72322 CPU either generates the tone or turns an oscillator circuit on and off.

    This is obviously a highly useful feature for 10M repeater use, and being able to change the PL/CTCSS tone frequency would be extremely beneficial to all owners of this rig.

    The answer, however, has evaded me. Anyone able to shed some light on this mystery?
    Last edited: May 17, 2019
  2. K8JD

    K8JD Ham Member QRZ Page

    I have had my HTX 10 forever (bought from RadioShack, Cheap, when they discontinued the model) and I can not recall any mention of CTCSS tone capability,.
    Possible to connect an external CTCSS generator to the deviation pot inside the radio.
    I mainly used this rig for SSB and some FM simplex on 29.600.

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