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Simple 400 Watt
RF Amp for
80 meters

VFO for 160 & 80 meters

Pulse Width Modulator and power supply

24 MOSFET RF Amplifier - Step by Step

Analog Modulator (Class H) and power supply

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and Parts


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The class H modulator - power supply by WA1QIX


This is the new class H modulator and power supply, combined into one enclosure.
The modulator will modulate a 360 watt transmitter, and the combined supply and modulator will deliver 45V at 8 amperes.


This picture shows the inside of the modulator, with the PC board. The heat sink and the MOSFETs are in the background.


Here is a closeup of the modulator showing the MOSFETs and source resistors.


Here is the modulator board.
This version of the modulator uses the PC board designed by KD1J which
implements the class H modulator described elsewhere on this site in a
reproducable and easy to assemble PC board.

This particular physical layout has the modulator MOSFETs located away from the PC board,
however it is also possible to connect the MOSFETs directly to the PC board,
making for a very compact and clean package.


Here is a picture of the low voltage power supply board.
The integrated power supply provides 62VDC and 130VDC for the modulator and
RF amplifier. The power supply features a step-start for surge reduction,
overload shutdown and control circuitry.

Metering is provided for all critical voltages and currents.

This modulator - power supply combination fits handily into an 8 inch high
rack cabinet and weighs about 35 pounds. The unit comprises the foundataion
to which multiple class E RF amplifiers may be connected, facilitating a
flexible and practical multiband transmitter.

The unit requires 120VAC, 8A and an audio input of 1v P-P (adjustable).
Combined with a high quality microphone, audio amplifier and peak limiter (plans
for which may be found elsewhere at this web site) you will have a complete
high fidelity, high power AM transmitter.