Independent Receiver Tuning For Transceiver

Did you ever wish you couid tune the receiver section of your transceiver without changing the transmitter frequency? Sure wouJd be nice on CW for setting the tone of the station you are workingt or for SSB roundtables where everyone never seems to be on the same frequency. It is extremely simple to do if you have an extra set of contacts on your TR reJay in the transceiver, or room for another relay. Stability is not affected; however, the vfo must be recalibrated. Such a device has been in use here for about three years, and I would be Jost without it.

Referring to the drawing, CR1 is a Varicap Diode Motorola MV1642 or Hughes 1M954. It changes capacity as the voltage to it is varied (working like a variable capacitor). When transmitting, the diode is given a steady voltage from the voltage divider RL R2f R3, R4, When in receivet the potentiometer R5 is supplying the voltage to the varicap. V/ith R5 in the center of its range, the control voltage is about the same as in transmit, so there wiJJ be no offset. Moving R5 above or below center will tune the receiver plus or minus from the transmitter frequency♦ Switch SI bypasses the offset control and allows normal tran sc e iver op era tion m

CI, C2, RFC1, and CR1 should be mounted inside the vfo enclosure* The other components can be anywhere, including a separate box outside the transceiver. Recalibrate the vfo with the switch in the off position, As shown, the offset is about 2 kHz. If you want more offset control change C2 to 10 pF.

I hope receiver offset will increase your operating enjoyment as much as it has mine. Cost is $6 or $7 if all parts are new.

Circuit courtesy WCRA SCOPE.


rCJ-HEF 500

Six meter pre-amp with 30 dB of signal gain and 600 kHz bandwidth. The input and output impedances are matched. AGC may be added to pin 5. For FM use dip the coils to 52.5 MHz. Circuit from Motorola HMA-36, Radio Amateur's IC Projects, avaiJabie free from Motorola, Dept. 73, Box 20924, Phoenix AZ 85034.

BRAND NEW FHEQ SHIFT TTY MONITOR NAVY 0CT-3: FM Receiver type, freq. range 1 to 26 MH/ in 4 bands. conl tuning. Crystal caljb. Reads up to 1 500 Hi deviation on built-in VTVM Cost £1100 00 each' In ungmat b»t, with instruct, book & cord, fob Mariposa CaL Shpe wl 110 lbs 49 50

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