In Memorium Wkxm

Licensed 1938

Edward "Corky" Gedney

December, 1903 July, 1972

HATRY ELECTRONICS Hartford, Connecticut transistors must have a high collector breakdown voltage.

Construction

The main chassis has to be drilled to mount the tube bases and modulation transformer or a subchassis can be mounted in a suitable place. The transistor circuitry is built on a piece of laminate board. Its construction is not critical as long as care is taken to avoid picking up rf. The leads to the input socket and gain control are made up of shielded cable grounded at one end.

The capacitor at the input to the second dc feedback pair is to decouple any rf picked up on the leads to the gain control.

In the prototypes, the B+ was 280V, the phase splitter had a supply of 50 V, and the front end 10V. Although the dc feedback pair is very tolerant with respect to supply voltage variations, should the B+ be much higher than 300V, the value of the first dropping resistor will have to be changed. The new value can be calculated using Ohm's Law.

The transistors used in the first dc feedback pair are a pair of 2N2926Gs. The second dc feedback pair uses transistors designed as Nixie drivers. Any type will do provided that their collector breakdown voltage is of the order of at least 80V.

By using dc feedback pairs, the circuit compensates itself for any change of transistor parameters, allowing type substitutions to be made.

The modulation transformer has to match into the final. The match is fairly critical; therefore, for best results choose a transformer that matches the final, although any old transformer will give some results. Results

I have had constant reports of good modulation depth, and good sound, while using tlie minimod in my subminiature 2m rig, No particular shielding has been built around it and it does not seem to suffer from rf breakthrough.

I would like to thank G8BEH for his help in developing the minimod, and for his patience in the testing.

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