Here is an Australian ham club's homebrew kilowatt amp using a pair of 813 tubes and a pair of microwave transformers in the power supply. Here is a link to WB8ERJ 's linear amp project using a pair of 813 tubes. The amp is under construction. More progress reports Pictures of the finished power supply I built are below. The magnetic shunts were removed from the microwave oven transformers as per the instructions in the articles noted above.

GOODSTUFF225 Lb - 2,800 VDC @ 2 Amps Continuous (Variac adjusts filament voltage)One of the least difficult and most expensive portions of any RF amplifier is the power supply. This is due, in large part, to the expense oflocating and purchasing a suitable high voltage transformer. To offset the cost, many builders attempt to build a doubler, or tripler circuit around a less expensive transformer, only to discoverthat the supply provides poor regulation and insufficient current to properly power the amplifier they worked so hard to build.

Such 'economy' power supplies do have a place, particularly when theintended power out is under a KW. Nevertheless, I have provided in this section circuitry utilizing both routes. In addition, I recommend that the builder study a bit about hv power supplies before attempting construction (see.Reference Material for suggested titles). A WORD OF CAUTION(fine print)Any voltage at or above 30 volts may be harmful to humans. Primary and secondary voltages described in this section and contained in actual components and circuits that may be constructed from theinformation contained on this page are LEATHAL and will very likely kill any of God's creatures that come in contact with them. Therefore, proceed at your own risk, with the warning that if you comein contact with the voltages present in the circuits and components described, DEATH WILL BE THE LIKELY OUTCOME.Below is a voltage doubler circuit, well suited for smaller, compact linear amplifiers.

For a full size image that may be printed, simply leftclick on the circuit image; when the enlarged diagram comes up right click on it, select 'Save Picture As', select a location and save the image, and click on the 'Back' button on the browser toreturn.The power transformer, T1, may be a 800-1000 volt unit capable of providing at least 800 ma. A safe bet would be a transformer capable of thosevoltages, weighing more than 10 pounds. Care must be taken not to attempt to exceed rating of the parts utilized.The diodes, equalizing resistors and corresponding capacitors may be mounted on an etched or simple perf board. Ceramic or bakelite standoffsprovide the necessary insulation and make mounting the board relatively simple. When assembling the capacitor stack, attention must be given to the fact that voltage will be present on the outside ofthe 'cans' and each must not only be insulated from each other, but from ground as well.

Placement of the swamping resistors that straddle the caps should have adequate ventilation. Additionalinformation on construction of the voltage doubler supply is provided below. Select 'NEXT' to continue.MORE GOODSTUFF.

HOME BREW
Compiled By AC6V

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CRYSTAL SETS TO SIDEBAND-- Free On-Line -- A Guide to Building an Amateur Radio Station By Frank W. Harris, KØIYE

HomeBrewHF High Performance Tranceiver (HBR2000) -- CW/SSB 160 to 10 meters, 6 wattsoutput, full QSK on CW -- From Markus Hansen, VE7CA

Ham Homebrew Digest -- Hundreds of Them

SM2EZT - Modified R2 receiver with DDS VFO.

SM6LKM -- Optimist-80 - QRPp DSB transceiver for the 80 meter band (1 WattP.E.P.)

A QRP SSB Transceiver -- By: Paul R. (Bob) Alexander, WB9IPA

Tuna Tin Two Gallery! -- Sponsored by ElectronicsUSA.com

Tuna Tin 2

NS8O - 160m CW/SSB transceiver

Optimist 80m DSB 1 watt TX -- By SM6LKM

VK2TIP Ian Purdie's radio design - WOW -- Ya Gotta See This One

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GU-84B HOMEBREW 2 TUBE8KW+ HF AMPLIFIER -- From Chris NI4L

Scratch Built RF Amplifiers -- From Bob, WB0NNI

Amplifier, Theory, Upgrades -- AG6K, Richard L. Measures