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Tod view of the transmitter shows the —150 volt bias supply and coaxial relay on the left and but* terfty tuning capacitors in the center.

A grid-dip meter or other frequency indicating instrument must be used during the initial tuneup. Since this transmitter was originally designed for operation on any frequency between 100 and 156 mc, its tuning range is quite w ide. In addition, the variable butterfly timing capacitors operate over a 90° range as opposed to the conventional 180% so some method must be used to ensure that each stage is operating at the correct frequency. As an aid to subsequent tuneups, all of the variable capacitor control knobs are oriented so that they point straight up when the transmitter is ready to go on two meters (see photograph), The stages are initially tuned as follows: Crystal Oscillator/Doubler 6AQ5A 16 mc Tripler 6CL6 48 mc

Tripler/Driver 832A 144 mc

Final Amplifier 832A 144 mc

Any high-voltage power, supply that provides from 300 to 600 volts at about 235 milliamps and 6.3 volts a-c at 6 amps is suitable for the modernized SCR-522, This may be realized quite easily with an old 1 V power transformer and silicon diode circuit wired as shown in Fig. 4. Occasionally the RA-62B power unit appears on 'he surplus market at a nominal cost; this unit was designed specifically for the job, but requires the use of 12.6 volt filament tubes.

This transmitter has been used for several months and has provided good performance both as a two-meter transmitter and as a driver for 432 mc gear. 1 lie modulation is exceptionally clean and has resulted in many excellent reports. On two-meters, Q5 contacts have been consistently maintained over 75 mile paths using this transmitter and a ground-plane antenna. A in all, it has proven to be a worthy investment for the small amount of time and money involved,

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