J.F.Drew © 2000-2017

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Calculate the frequency jumpers on RX & TX of PRF1520

The jumpers on the PRF1520 can be a pain to calculate and the original program from the manufacturers has a bug in the receiver calculations.

This program calculates and determines if, given the crystal and the spacing, whether a possible frequency may be achieved. The operation of the program is self evident.

Download here.

The permitted oscillators are:

(1) 5.12 MHZ for 5kHz and 10kHz channel spacing

(2) 7.68 MHz for 30kHz spacing

(3) 12.8 MHz for 12.5 and 25kHz spacing

Options do depend on the settings of links on the receiver or transmitter boards. For example a radio may be either a 12.5 kHz separation or 25 kHz channel separation depending on the settings that follow.

See LK1,2,3,4,5,6 on the receiver (solder style links)

and LP4 on the transmitter (pins 1-8).

See the manual's documentation for the above.

I have allowed calculations of TX and RX frequencies even if the channel spacings and crystal do not allow

it. Generally the advisory of "Spacing OK" should be followed.

Note that even when spacing meets crystal criteria, some frequencies cannot be set as the programmable

divider cannot find an integer solution.

In July 2024 I’ve added facility to determine the unknown frequencies of a newly obtained radio. This is now in a separate lower section of the program and relies on setting the jumper positions in the program.  In addition it is necessary to set the Separation, Xtal frequency, displacement of RX oscillator and the IF frequency. Using the bottom section below the red bar the transmitter and receiver frequencies may be calculated.

John Drew VK5DJ

4 July 2024

(Original version in April 2019)