> Here is a grab from the Eimac data sheet at the Eimac
> website.
> seems to me 6 meters is covered nicely by this tube.
> RADIO FREQUENCY LINEAR AMPLIFIER
> CATHODE DRIVEN
> (Frequencies to 110 MHz)
> Class AB2
Lou,
Just because a single tube will operate at full ratings
under controlled conditions to a certain frequency doesn't
mean it will work in any layout to that frequency. It also
does not mean it is the best choice right up to the limit.
I have no doubt at all a pair of 3-500's will work OK on six
meters once the basic recipe for layout, parasitic
suppressors, and so on is learned. That of course never was
a point of debate because it's possible to make terrible
tubes like 572B's or sweep tubes work up to and beyond their
published limits.
But since you brought up the frequency rating it is worth
bringing up the general rule of thumb. The higher the
frequency rating for full power the easier the tube is to
stabilize at upper HF. As a *general rule* we want the
maximum full power frequency to be around three times the
highest operating frequency or higher for the easiest and
least critical design. The wider the spread between maximum
and operating frequency the easier it is to work with the
tube and stabilize the tube.
This is why tubes good to upper VHF or lower UHF are so
non-critical on ten meters compared to tubes that fall off
the porch at 60 MHz.
This is always something to keep in mind when picking tubes.
73 Tom
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