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since March 17, 2008

Amplifier Project

After starting down the road to station automation by purchasing band decoders, a DX Doubler and Six-Packs in 2007, I realized that having just one manual tune, tube amp would not allow the station goals to be met. After much prompting by K5RUS, a broadcast engineer here in Monroe, and additional consultation from K5OR, a structural engineer who enjoys homebrewing, I decided to follow the lead and build a legal limit, solid state, no tune amp. Several additional sources of information are listed at the bottom of this page.

This amp is based on the MRF-150 FET, and the design of Helge Granberg. The project will use EB-104 boards from Communication Concepts, each holding four of the FETs, with an input of 6 watts and an output of 600 watts. The amplifier will consist of FOUR of these boards, which will yield a possible output of 2400 watts. Circuitry will be employed to eliminate any chance of exceeding 1500 watts, giving a "headroom" of 900 watts. This will allow the FETs to run at about 60% of rated output, allowing cooler operation and the ability to operate into "less than optimal" loads. 

With each EB-104 board requiring about 21 amps (@ 48 volts), it will take a pretty hefty power supply. I have acquired several Lambda^® switching supplies which incorporate a "tracking" feature, so they will be connected in series/parallel to provide the required wattage. Yep, that's going to be 85 amps at 48 volts. Glad I ran that dedicated 60 amp 220 volt line to the shack!

As an "all Icom" station, I plan to employ built-in band decoders to allow the amp to auto-track the radios, with manual selection as an option. The decoders will select appropriate internal bandpass filters to keep harmonics within FCC standards. I may use a PLC to handle all oversight (heat and SWR sense), cooling fan speed, etc. Not sure whether it will run fast enough to handle keying or not, haven't gotten that far. As primarily a phone op and a casual CW op, I am not sure whether it is worth the extra trouble to add full QSK capabilities or not. Will have to think about that.

Photos are posted  HERE to document the construction.

As the project progresses, and I remember to take some photos, I will update the page.

K6IF's Project Gamma

K0GKG's single board, 600 watt version

WM5Z's version

K9HZ also provided some useful information

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