ed for a null. Set the ceramic trimmers across the carrier oscillator crystals at minimum setting and while switching from USB and LSB positions check to see that the VTVM reading remains about the same. rhis indicates that the crystals are centered reasonably well on the filter curve. Proceeding next to the 7360 mixer, place the probe on pin 9 and adjust both windings of T2 for a maximum reading, Then with 41.1 MHz energy applied check pin 3 for a reading. It should be about 1 volt with L3 adjusted to resonance. The next step is to remove the 6AU6 if tube to prevent 9 MHz energy from reaching the 7360. With the probe at the center-tap of L2 adjust the 5K 2w potentiometer for minimum 41.1 MHz feedthrough.
Apply voltage to the 12BY7 with a temporary jumper and with the probe at pin 5 of the 2E26, peak L2 and L4 and adjust L5 by the "squeeze" method. Moving the probe to the plate of the 2H26 adjust C and/or C2 for minimum feedthrough of 50 MHz signal.
A fairly satisfactory alignment of the carrier oscillator crystals can be accomplished as follows: with the rf probe at pin 9 of the 7360 mixer and with some carrier inserted increase capacity across the 9.0015 MHz crystal in order to move it down into the filter passband. Note the VTVM reading and then adjust the trimmer to yield a reading approximately three-quarters of the "passband" reading. Set the 8.9985 MHz trimmer to give a similar reading.
Some builders will wish to modify some of the circuitry to fit their likings and their junk boxes. One improvement would be a four position function switch to allow for a "manual" operate position. In the control section, by use of the negative bias voltage to disable the low-level rf stages one could use a relay with fewer contacts. Furthermore, only one side of the ac line need be opened for the switched 117 VAC
The idea of tripling in the VXO tube was suggested by W2AL1 and has proved very satisfactory- VXO shift was held to approximately 40 kHz to give maximum stability, but with more series inductance coverage of 100 kHz should be possible with good stability.
Building the exciter consumed quite a few hours of my spare time, but I enjoyed it, and am looking forward to building a transistorized version in the future.
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