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Fig. 1. Transmitter schematic.

the first time the key is closed. These features should make this a project that both the Novice and old-timer can enjoy

My original design called for vfo control ot the transmitter, but that required five rather than three transistors. Additionally and more importantly, the components needed to construct a stable vto cannot be purchased at most Radio Shack outlets. To overcome these problems, crystal control was decided upon At first thought, crystals conjure up an image of hours of operating without a contact as you wait for someone to happen upon your frequency That simply isn't the case, as will be shown later, Also, since Novices now can use vtos, there are many crystals lying around in ham shacks everywhere.

The transmitter can be built as a basic unit or with several options, as shown. The basic unit consists of the loaded PC board soldered to an antenna connector and power source If the transmitter is to be used for serious operation — which it definitely is capable of —then the options, which require onlv a little more time and money, should be added. Options will allow T-R switching, some frequency variation, two bands in one boxr and a package that is more pleasant to look at and show ott

The Circuit

As can be seen from Fig 1, the transmitter meets the design goal of being simple Only three transistors are used to generate the 5 Watts of output power. Resonant circuit inductors are formed using iron-core rf chokes. Common-value ceramic capacitors are used either singly or in parallel to obtain the needed capacitance.

Q1 operates as a Pierce oscillator at the crystal frequency. PT-24J crystals, which are inexpensive and plentiful, can be used. Output is taken from Q1 by a five-turn link over IK Q2 and Q3 comprise the class C final amplifier and are operated in parallel, Parallel operation provides an easy method of obtaining the desired 5-Watt output

The parallel combination of Q2 and Q3 presents about a 60-Ghm load to be matched to the 5G-Ohm antenna load. This collector impedance is determined from the formula f?L -Vcc3/2po, where Vcc = 24 V and po - 5 Watts.

The impedance transformation is accomplished with a pi-network corn-posed of L4, C4, and C5. This network also offers harmonic attenuation to the signal The transmitter, as designed, easily meets the FCC regulations tor harmonic radiation

Photo A. Completed transmitter.

R5 and R6 are used to equalize current flow in the two transistors, in all of the units built thus far, I have detected no "hogging" of current by either transistor Nothing special has been done m selecting matched transistors. If they run equally hot, they are matched ^ell enough! Heat smks are needed on both

Photo B. Sack view.

transistors to dissipate the type of heat sink needed is heat generated, S inee the not available at Radio

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