(Nov 20 2012)

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MGF1801. Input side. Here one can see two low loss 24 pF capacitors from the drain to the source ground plane. The source ground plane is decoupled to ground with 8 capacitors 1 nF each evenly spaced around the ground plane and to the screening wall between the input and output compartments.

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MGF1801. Output side. The output tuning is a PI filter. The 48 pF fixed capacitance has a trimmer in parallel. There is a DC blocking capacitor in between. The inductance is a slightly bent 1.5 mm enameld wire and the output capacitor is 33 pF with a trimmer in parallel.

The output could be re-tuned to 50 ohms, but since several measurements have been made on this amplifier before I decided to not change anything. Neutralization is via a phase inverter made from a few turns tvisted wire wound on a small ferrite tube.

The drain voltage is set with a potentiometer followed by an emitter follower to 3.68 V. The source resistance is set to 46 ohms with another potentiometer which gives a current of 30 mA through the transistor.

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MGF1801. Input impedance and forward gain.

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MGF1801. Output impedance and reverse isolation.

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