Circle On Reader Service Caro

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CIRCLE 2&6 ON READER SERVICE CARD

lator radiation and hand-capacitance. It takes some extra work over that of a breadboard layout but is worth it. I also recommend mounting the PC board with a l/2"-thick piece of foam rubber sandwiched between it and the chassis, using double-sided adhesive tape. This helps reduce any tendency for microphonics.

The only potentially tricky part in as* sembling this project lies in getting the secondary of L2 wired in the proper direction. Connect a short (one foot is line) antenna to the "Hi Z" antenna terminal, turn on the power to the unit, then advance the volume control to its midpoint while listening to the outpui on your headphones. Slowly rotate the ^Regeneration" control from one end of its range to another You should notice at some point in its travel a fairly abrupt increase (or decrease) in au dio noise in the phones, indicating thai oscillation has begun. If the noise level in the phones remains constant while rotating the "Regeneration" control, you probably have L2's secondary wired in reverse. Swap the ends of the winding, and try again. If there is stilt no change, try increasing the number of turns on the L2 secondary from two to three, and repeat.

In operation, the receiver is surprisingly sensitive. With a 1-foot antenna and no ground, 1 was able to pick up over 2 dozen broadcasters. With the regeneration control at the threshold of oscillation, the selectivity was such that there was no adjacent channel interference, and the headphone volume was more than adequate, Pretty impressive for 80-year-old technology! 1 would tike to think Howard Armstrong would approve. EQ

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