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Thread: Quantar VHF R-2 over deviation on P-25 help

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    Default Quantar VHF R-2 over deviation on P-25 help

    I have a Quantar, VHF, low power R-2 with firmware 10. Programmed with R14.10. It operated fine in analog but will not pass through P-25. It shows on the SM > 5.0 on P-25 dev. In the test mode. The soft pot will only allow me to go to 1.9 at 150.00 Mhz and 2.0 on the subsequent settings. Any ideas?

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    What SM are you using and what setting do you have? Suggested reading:
    And the real Quantar service manual

    My approach is to use an HP 8901B modulation analyser.

    Step one make certain the station is on frequency (reference alignment). This is most easily done by injecting a 10 MHz reference (needs to be a good TCXO or better, preferably an OCXO or GPS disciplined reference). I cal my 8901B OCXO against GPS then use the 10MHz output as a reference for the Quantar. If you don't have a standard don't touch it.

    Now using an the 8901B modulation analyser you need to set the LP filer to > 50 Hz and the HP filer to < 20 kHz and +/- peak.
    Connect a 'scope to the 8901B audio output and follow the alignment procedure to get the required reference modulation compensation (flat tops on the 'scope waveform) and the deviation alignment. The last two adjustments slightly interact.

    The goal in normal operation is 2.83 kHz for your transmit frequency.