R.L. Drake

Drake Mods - Synthesizer

Authored by VE3EFJ


    The synthesizer requires programming in order to set the correct 1/2 MHz range. This requires some calculation. The pins A0 to B3 comprise a 1 byte field to indicate the correct .5 MHz chunk. You simply cannot assume that 18 MHz is the 36th 1/2 MHz chunk and program '0011,0110', for there is a modulus to be accounted for.

    The formula is 86 - (f*2), where f is in MHz at 500 kHz settings. To set the synthesizer to 27.0 MHz, you would calculate 86-(27*2) = 32 = 0011,0010.

               0 0 1 1, 0 0 1 0         PIN
               |     |  |     |         ===
               |     |  |     |___ A0    2
               |     |  |_________ A3    5
               |     |____________ B0    6
               |__________________ B3    9

    To program this 27.0 matrix, you would connect diodes from pin 1 to pins 3,6,7 for the synthesizer, diodes to pins 11 and 14 for the band switch, and a diode to pin 10 to enable transmit. (but we'd NEVER do that, would we?).

    The TR7 has 2 master oscillators that are selected by the band switch, NOT the frequency programming. Although it is not obligitory for reception, you should also program the band switch data so the SETBAND light will come on. A common error is to do the diode programming, fire it up and the synthesizer won't lock. This is usually caused by the band switch in the wrong position. The band programming and the SETBAND light is designed to prevent this.

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