Project HF-1200 power amplifier
When I thought about what I would like to build, the desire for
a transistor power amplifier came up.
This should be cheap, run stable, without tubes, no tuning, be quiet and of course reach the 750W without problems and have power reserves to not have to work at the limit.
When I started looking around, I discovered a power amplifier that was cheap to build with IRF MOSFETS. The cost was about €0,65 per piece and a design I found at first also good. Thereupon I collected further information and prepared an OV project. Clearly the project had to be rebuild-safe and if already OV project then also correctly. I had to explain and discuss the circuits of the individual components, and then get to work with the soldering iron. Everyone who participates should not be a technician, but should at least understand the basics of what he is building and why it works in the end.
However, I was bothered by the voltage supply of 100VDC which was often obtained directly from the 230VAC, for me an absolute no-go! After the toroidal transformers became quite expensive, another solution was needed. By chance I could get new server power supplies from a supplier, 50VDC 57A. With that you can start something!
If you now have cheap 50 VDC available, you might as well find real RF MOSFETS, preferably still affordable ones.
I decided to completely discard the work of the last few
Something new with the Microsemi VRF2933 on which I had set my
sights. But that also meant developing my own PA module. But
that was not the end of it! A really large part of the time I
turned to the topic purchase. Searching for components,
comparing dimensions and technical data, getting prices and
that in the USA, Europe and Asia. Of course the effort PA
Develop low-pass filter, develop control, measure, regulate and switch with the Arduino. I had no idea about the latter, but I have my own principle:
What I can't do I will learn, so I learned C/C++ !
So it took a good 3/4 year until my first power amplifier was ready, but it was worth it. A coherent concept was created, which does not have to hide behind the commercial manufacturers.
If I reach a temperature of 48°C after two hours in contest mode with a QSO rate of 80 QSO's per hour at 1kW output power, then I think I have done everything right.