[Amps] Amp design article?

[Catherine James]

Karl-Arne wrote:
> ...I got a preview at the factory in Pomezia of the new generation of SELEX 5 and 10 kW solid-state
> transmitters using plastic cased MOS-transistors. Each module uses 2 transistors, and 12 modules
> are summed toprovide 6 kW from each half in the 10 kW unit... The very reliable Rockwell-Collins
> PA-2250, directly derived from the HF-8023, used the same approach to reach 3 kW with bipolar
> transistors as did the, alas short-lived, PA-2224 which used 16 MOSFET modules to reach 4 kW.

Manfred wrote:
> I would look for devices designed specifically for linear service. These have a relatively high
> power dissipation rating, compared to their output power rating. For example an ancient
> Motorola PT9780 transistor, of which I have a bunch in my junk box, is rated for 100W RF output,
> and 350W dissipation... There is an increasing number of hams using homebrew amplifiers
> that use 16, 24, 32, or even 48 cheap 1-dollar MOSFETs. Those FETs are much like your
> IRF510, only for higher voltage. The IRF710 is a typical one used in those amps.

Doug wrote:
> I have 32 BJTs in my push-pull parallel design. Once a single 220 Watt module was designed
> with lots of negative feedback, and its own self-contained switching power supply, it was easy to
> splitter/combiner my way to full power. The advantage of such design is that I simply don't
> supply mains voltage to one or more modules, and I have instant lower power... I have a fan on
> each module, but they are thermally controlled in a PID loop.  At 2 kW into a dummy load, I
> can just hear them spinning.

You guys should publish a construction article(s) in QST and other nations' equivalent magazines. A lot of us would love to build such an amp, but we're not competent to design it.  Being able to work with off-the-shelf, widely-available BJT or FET components in current production, and off-the-shelf heat sinks that don't require custom machining, should bring the cost and skills required down significantly.

73,
Cathy
N5WVR