Info

Area Code 605

WATERTOWN, SOUTH DAKOTA

I'bom Credit: Jot Dé Young WA6CQL

Jim Kennedy K6M10 2816 E. Norwich Fresno, Col if.

UHF Signa

Generator li operators on our sparsely populated l"HF bands were obliged to wait for the appearance of an air signal on the band in order to align a converter or tune up a preamp many would probably grow long grey beards (apologies to Sain Harris) before the converter or preamp was ready to go.

Front view of signal generator.

Having worn out several razor blades over this problem myself, I set out to seek a solution to the problem.

Investigation revealed four possible solutions: buy an electric shaver, convince more bams to build IHF transmitters, quit ham radio forever (again?), or build a signal generator.

All of these were tempting but the last was finally decided upon.

Several requirements were the basis for the design of this signal generator: operation on both 432 mc and 1296 mc, high stability e.g., crystal control, variable rf amplitude, provision for insertion of various types of modulation, and lowest possible cost consistent with satisfactory operation.

I had a 27,005 mc overtone crystal left over from a brief period of disillusionment about CB and, since 27 times 6 is 432 which times 3 is 1296, this seemed a likely place to start;

Fig. 1 shows the final result. The overtone oscillator is voltage regulated and is left operating at all times when the generator is on. The crystal is mounted underneath the chassis to protect it from rapid temperature changes from drafts, etc., further enhancing the stability.

The use of diode multipliers at 132 mc and 1296 mc greatly simplifies developing UHF rf.

Direct coupling the modulation into the cathode of the last vacuum tube multiplier provides a modulation input that will accomodate almost any signal from audio to video, or even pulse.

A four position mode switch on the front panel allows the choice of carrier, no carrier, carrier with 60 cycle modulation and finally carrier with external modulation.

Closeup showing the oscillator and vacuum tube multipliers.

Construction

Building the unit presents no special problems except getting it all under the chassis. The 5 x 9M x 2% chassis doesn't leave much useful room to spare, but it does make for a very compact device.

The lengths of the diode multiplier tuned lines were determined primarily by the space available and bear only the slightest relation to the wave lengths involved; hence, it was necessary to pad both lines with additional capacitances in order to resonate them properly.

Both lines were folded from 1/32 inch brass sheet stock. The inner conductors are made

20,000 OHMS per VOLT DC

1 % Precision Resistors

Closeup view showing details of diode multipliers lines.

Alfow 50c for packing and shipping-California residents include 4% sales tax.

1000 SOUTH ÖASCOM

Northern California's Mast Complete Ham Store

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