97.4PL not supported by Kenwood TS-811/TS-711?

Discussion in 'VHF/UHF - 50Mhz and Beyond' started by AD8BU, Oct 10, 2019.

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  1. K7JEM

    K7JEM Ham Member QRZ Page

    You could add an external oscillator and switch between the two oscillators, the original 1MHz and one that generates 974 KHz. If that was switched in, you would get 97.4 Hz when the 100Hz tone was selected. Programmable oscillators are available for a couple of bucks that could do this, it would be some work, but be relatively cheap.
  2. KA9JLM

    KA9JLM Ham Member QRZ Page

    97.4 should be tone 1Z.

    What repeater uses that tone ?

    Check the tones from the top down. It may be there near the top.
  3. K7JEM

    K7JEM Ham Member QRZ Page

    1Z is 100 Hz. 97.4 is ZB
  4. AD8BU

    AD8BU Ham Member QRZ Page

    That might work if I can't get my hands on the MX915AP chips. The chips I found on Ali Express are about $11 USD for 5 of them. I think I will start with that route, and if I can get my hands on those all I need to do is swap in the MX915AP and add a SPST switch to pin 2 of the chip to get all three additional tones. Of course, I would have to manually flip the switch when I want to use a repeater that has 69.3, 97.4, or 206.5, and remember to flip it back when I use another one. I would just have to program 94.7 as 74.4, 69.3 as 79.7, and 206.5 as 85.4.

    Per the data sheets, the MX915 series has internal pull up resistors and the tone can be changed "on the fly" making it a very simple mod. The clock, however, cannot be changed "on the fly" as there has to be a clock signal if voltage is applied to the chip.

    If I was REALLY smart, I'd dump the code for the ROM in the TS-811, mod it to include the three extra frequencies, then burn it to a new chip... But, I am by no means a software engineer. The most advanced hand coding I have ever done is G-Code back when I was in college...

    444.7MHz... https://www.w8mai.org/index.php/club-information/repeaters-and-nets
  5. K7JEM

    K7JEM Ham Member QRZ Page

    Is there a MX915A chip, or do you mean MX315A chip?
  6. AD8BU

    AD8BU Ham Member QRZ Page

    Meant MX315A... oops.
  7. K7JEM

    K7JEM Ham Member QRZ Page

    If you put that switch to ground, you may want to install a series resistor between the uP controller and the TU5 so that you are not directly shorting its output. Something like a 2.2K ohm should work OK. Depends on what the internal pull up resistor is in the 315 chip, but most are greater than 10K.

    Document what you did to make it work, then sell the excess chips for more than you paid for them.
  8. AD8BU

    AD8BU Ham Member QRZ Page

    Ahh, I get it now...

    I was just gonna use an SPST switch to make it an open circuit to create the logic high on the MX915 (its inputs are inverted), but I suppose I should provide a path for the electrons coming out of the I/O interface on the transceiver. Switching in the mentioned resistor might work, and not require me to break a trace on the TU-5 board...
  9. AD8BU

    AD8BU Ham Member QRZ Page

    Looking things over again, I am getting things backwards in my head...

    The inputs to the MX315(A) are inverted. I wound need to force 5 v onto pin 2 in order to convert the tones.

    I can try using some signal diodes to accomplish this with a SPST switch, but the voltage drop through them may be too high.
  10. K7JEM

    K7JEM Ham Member QRZ Page

    No, you have it right initially. If you program 74.4 and ground D2, you will get 97.4. So a spst to ground on D2 will work.

    The problem is that the microprocessor controller is outputting a 1, or 5v. If you ground that input pin on the 315, you are also grounding the source pin on the controller, creating a short circuit to ground directly on that output pin. If you insert a current limiting resistor on that path somewhere, it won't matter that you ground D2, the controller will just apply voltage to a 2.2K resistor to ground, which will not hurt it. You will have to break that path somewhere to insert the resistor, however.
    AD8BU likes this.

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