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

Subject: Re: [Amps] Tube amps are not a thing of the past - nor is the 2N2222
From: Manfred Mornhinweg <>
Date: Mon, 05 Jun 2017 16:18:55 +0000
List-post: <>
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!


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