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FT-817ND Range extender!
Homebrew - Saturday 9 July 2011 20:50
 
Although I very like QRP. And I very like my FT-817ND. But sometimes you wish you had a few extra Watts. Especially on the low bands 80m and 40m.

5 Watts SSB on 80 meter is most of the time too low. So I build an amplifier. It's build with 4 x IRF510 in push-pull. VCC is about 26 volts. 1 Watt in is 100 Watt out. I have an attenuator so I can drive the amp with 2.5 Watt. Current is about 7 amps. So the efficiency is about 55%. The idle current (bias) can be adjusted per individual IRF510.

There is A tiny micro-controller (Attiny45) with an LM35 temperature sensor to regulate the fan. Although fan control can be perfectly done without a micro-controller. I think no project is complete without A micro-controller! Every project of mine must include at least one micro-controller! They are so cooool :-)

I have only build two low-pass filters for 80m and 40m yet. Maybe I build a third one for 20m.
The heatsink is an old Pentium 3 heatsink. This amplifier can be build under 25 euro's :-)
It doesn't have SWR protection so if I blow the fets it will cost me about 5 euro's.

By: Erwin | Permalink | 1 comment