What does the Reference Frequency setting do?

Although hardly ever used, the Reference Frequency setting in the CPS can be used in very specific circumstances to eliminate self-quieting, when receiving on specific frequencies that would otherwise be blocked by internally generated spurious signals.

Internally generated spurious signals would appear as weak silent carriers on certain frequencies.
Shifting the reference frequency allows these permanent signal carrier to be shifted to unused frequencies so that the desired channel frequencies can still be used. The options in most MOTOTRBO radios are Default; Nominal or Alternate.

There is also a Reference Frequency setting for TX. This is the same as the one for RX but in this case, the reference frequency is shifted during transmit and is intended to prevent the transmitting radio from interfering with other radios which are closeby (i.e with a meter or do) in certain circumstances.

If altering the Reference Frequency setting does not resolve the interference, then the issue lies elsewhere - not the radio. Altering the Reference Frequency setting won't have an impact on frequency stability and the radio should otherwise perform normally.

From experience, for 99,999999999999999999% of cases, you can leave this setting on Default.


  1. So what I understood. Example my rx is 156 mhz and I decide to take 2.2 mhz as the reference frequency then it means that my reception frequency becomes 158.2, and I have to change the reference frequency of the portable.
    This does not infect any other frequency that uses 158.2 as rx?

    1. No, all this does is shift the internal clock so that it doesn't interfere with certain RX frequencies. You would only change this setting if you come across a signal that doesn't disappear when you remove the antenna.

    2. For example, the 19,2MHz clock signal on some models will produce a harmonic at 153,6MHz. If the radio receives on this frequency, a continuous unmodulated carrier will be heard, even if the antenna is removed. To avoid this, you can change the Reference Frequency setting so that the clock is shifted to 9,6MHz which wouldn't produce a harmonic 153,6MHz. (153,6 = 19,2 * 8)

  2. Hi, Mr Holmes.
    I'm Korean Engneer.
    We use the 400Mhz Frequency.
    This behavior is impaired.
    The average value 95~110RSSI value.
    Sometimes 40RSSI signal comes in.
    Is the solution to this problem changing the Ref frequency?
    If change, choice Nominal, Alternate
    What should I choose?

    Please answer this question by all means.
    I am desperate


    1. First you need to verify whether the signal is coming from the radio or something external. The easiest way to do this is to remove the antenna: if the signal is still there with the antenna off, then it's coming from within the radio. To be 100% sure you may need to go into an area like a field or into the basement as sometimes it's possible to pick up strong signals with the antenna off.

      If you've established that it's the radio doing this, you will need to experiment with this setting to see which one works.

      If you are using 400,0000MHz, this in itself may be a problem as ,0000MHz frequencies tend to be noisy due to IT equipment generating spurious signals at these multiples.

    2. Thank you very much.
      Let's try it.
      The frequency is not exactly 400mHz.
      For example, I have said so (Please note that the exact frequency can not be illuminated).

      If the antenna is removed and the value of 40rssi comes in, is it correct to change the Ref Frequency?

    3. That's okay, I understand.

      If you remove the antenna and are certain that there is nothing external generating this signal, you can then try changing the Reference Frequency. This might help.

    4. This comment has been removed by the author.

  3. Let me ask you one more thing.
    if you change value
    nominal or alternate??
    What is your choice??

    1. You'll have to try both and see which works the best.

    2. OK. Thanks you, Mr.Holmes!
      God Bless you :)


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