Output To

Fig. 5. Diagram for the oscillator tripler.

L2— 15T #28 ClosewoLind on form, Link 2T of hookup wire.

XI—FT243 surplus xtal, A 6.850 mhz crystal will give a spot frequency of 50.100 mhz a similar fashion the primary and secondary of T2 are lowered in frequency.

Some will argue that L\ should be bifilar wound- Both a conventional and bifilar winding were tried and no significant difference in carrier suppression was noted. The differential capacitor associated with L\ was constructed by taking a regular air trimmer, setting its rotor at half mesh and after inserting cardboard wedges between the s tat or plates, cutting through the stator with a fine toothed hacksaw blade. Of course this capacitor is available as a regular item if you can get your hands on one.

The 2E26 final is stabilized with capacitive neutralization. Capacitor C] should be mica and will be in the 330 to 560 pF range while C2 is simply a stiff wire passed up through the chassis into the final amplifier compartment and placed near the tube plate.

Tuneup and Adjustment

It is assumed that the constructor will have checked all coils for approximate resonance (with the tubes in their sockets incidentally). Applying line voltage and setting the function switch in the standby position will place plate voltage on all stages up to the 12BY7 driver, A VTVM with an rf probe is almost mandatory for tuneup, Place the rf probe at the 6AU6 grid pin and adjust the carrier balance control to secure a reading. With the differential capacitor set at center adjust L] and T] for a peak reading. The differential capacitor is then adjust-

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