The 15 db rule applies only to manufactured for sale amplifiers. It
does not apply to amplifiers that an individual ham builds for him or
herself, particularly when a a kit is not involved.. Section 97.317 of
the rules, which is where the 15 db rule appears, applies to the
certification of external RF power amplifiers that a manufacturer offers
for sale. Home-made amplifiers do not require certification. They must
still meet some standards, such as those involving purity of emissions
(harmonics, for example) and of course must not be operated above 1500
watts PEP, but that's pretty much it.
I am unsure of how the rule applies to kits, but I think they would be
considered a "manufactured product" if all the parts needed to complete
the amplifier are contained, in the kit. If, however, a "kit" contained
only some of the parts, and could not in itself be assembled into a
working amplifier without adding extra parts, then the certification
rule probably would not apply.
It would be perfectly legal for a ham to build a home-brew grid-driven
amplifier that could take the 10 watt signal from his K2 and boost it
to 1500 watts output. Such an amplifier would have (roughly) 22 db of
gain. A pair of 4CX800 tubes could accomplish this, I think.
Remember also that the old Johnson Thunderbolt could be operated in
grid-driven mode, and it had (still has, if you can find one) similar
performance, using a pair of 4-400 tubes.
- Jim, KL7CC
Chris Kantarjiev wrote:
The Linear Amp kits seem to need a fair amount of drive. I've been
idly thinking about a linear that would allow me to drive it with
my barefoot K2 and get 600-800 watts out for CW.
The limit is 15 dB and is still in the requirements despite the
recent loosening of Part 97. That should give something over 400
watts when driven by a K2. I don't recall whether the "easily-
modifiable" rule is still there, so it may be possible to have an amp
with an attenuator on the front-end (I heard that one of the Tokyo
High Power amps does this, but haven't verified that).
73, Bob N7XY
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