[Amps] Tube amps are not a thing of the past - nor is the 2N2222

[Manfred Mornhinweg]

Cathy, and all,

> Yes, ham gear needs to be based on the RF PA equivalent of the 2N2222 and
> 2N3055; devices that have many uses, are fully mature, and won't be readily
> obsoleted by new tech.

And why use "RF PA equivalents" at all? Why not use the 2N2222 for legal 
limit power amplifiers?

The 2N2222 can dissipate 0.625 watt in still air, without a heatsink. 
Significantly more if there is some airflow from a fan. Let's call it 1 
watt. It has a transition frequency of 300MHz, so it's perfectly 
suitable for operation to 30MHz, and with some loss of performance 54MHz 
is possible too. Its voltage and current ratings are fine to operate at 
either 12 or 28V, but its capacitances are such that 12V operation is 
preferrable.

So, let's use 2000 or 3000 2N2222 transistors in a push-pull/parallel 
configuration! With small individual emitter resistors to enforce 
current sharing. No heatsink required. Just mount them on several 
boards, stack those boards, and have a slow-running, quiet fan blow air 
through the assembly.

Cost? Almost nothing. I just checked: On eBay you can find a 1000-pack 
of 2N2222 transistors for 8 dollars, international shipping included! 
Yes, you would need more circuit board area than for an amp using big 
transistors, but that would be far more than offset by not needing a 
heatsink nor a spreader. The input and output trafos would be 
distributed too, using a relatively large number of small ferrite cores.

The power supply could be a dozen PC power supplies, costing $10 each, 
new. Or for casual operating use a truck battery with a trickle charger 
on it. Don't forget to use power wires as thick as truck starter wires!

It's just a matter of coming up with a clever layout that keeps phasing 
problems under control, then having the patience to solder all those 
parts, and there you are, with a legal-limit 2N2222 amplifier!

Manfred

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