On Sat, 3 Feb 2007 19:48:34 -0500, "xpyttl"
wrote:


Chances are, you might do some good with some of them on 80, but you're not
likely to make them play nice on 20. If you notice, the 3055 has an Ft of
2.5 MHz, 3054 3 MHz. The 2N2222 has an Ft of 250 MHz, so you can see
there's a little difference there.

Your 3739 has a 10 MHz Ft, so you might get a little gain out of it on 80.
The 2SC895 I *think* is 20 (could only find a bad copy of the datasheet).
It will take a fair bit of tinkering to make parts like that work at all,
and they won't work well.

The current gain drops to unity at fT, but you might still get some
voltage and power gain around such frequencies in a common base
configuration. This is the case in many microwave bipolar amplifiers,
since you can not get transistors (or would be too expensive) with fT
sufficiently high for common emitter configurations on a particular
band.

However, I have not seen common base amplifiers for HF, since RF power
transistors with sufficiently high fT are easily available for HF.

Paul OH3LWR