Schematic & Wiring Diagram

3W HF QRP Linear Amplifier

This is a rather abnormal QRP Ability Amplifier design, with a advanced abundance response; aural three dB's from 300KHz to 30MHz. Overall accretion is in the arena of 16dB and the final achievement ability may be able-bodied over four watts.

The advanced bandwidth is a aftereffect of the architecture of the RF transformers, T1 and T2. These are anguish on 2-hole ferrite balun cores as frequently begin in the old ancient valve TV sets (e.g. Phillips 4322-020-31520). Twist 2 lengths of 22 SWG enamelled wire calm and wind as shown. Connect the end of the "A" ambagious to the alpha of the "B" winding. Use this alliance as the centre-tap of the transformer.

This PA will bear 4 watts continuously (with a acceptable heatsink), and may be loaded into a circumlocute or accessible ambit after causing damage. This makes it about the ideal PA for outdoor/field use. Above is the abounding ambit diagram of the RFPA and the braid ambagious pattern. This PA may be acclimated for for SSB, as able-bodied as CW (and AM?).

Set RV1 to MINIMUM attrition and administer 12volt ability with NO DRIVE. Adjust RV1 for about 250mA DC absolute accumulation current. This may be be bargain to a abundant abate accepted if lower achievement admiral (reduced drive) is used.

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