[AMRadio] Can you have Class D and Class E tube amps?

Jim Candela jcandela at prodigy.net
Tue Dec 27 11:15:50 EST 2016

The classes of operation, a,b,c,d,e, etc. can be applied to solid state or tubes. The Retro75 and Retro40 transceivers made by Small Wonder labs used a class D RF output stage using a power FET followed by a LPF. Both class D and E can use sine wave drive, or preferably a single polarity pulse that is about 40-45% the width of a half cycle. The output circuit for class D is a LPF, and for class E, it is a resonant tank. Class E is usually a little more efficient, but class D is simpler in that no tuning is required.
For 137Khz, if the old 1 watt DC input rule is still in effect, you want the highest efficiency possible. Therefore class E would be desired. Should be able to get 95% or higher efficiency.


    On Tuesday, December 27, 2016 8:32 AM, Rob Atkinson <ranchorobbo at gmail.com> wrote:

 That's right, Bob in Penn Yan and the other guy is I think John K5PRO?
 I think he has one.


On Tue, Dec 27, 2016 at 6:16 AM, Mike Sawyer <w3slk at verizon.net> wrote:
> I think W2ZM uses one of those on 160M frequently. I remember seeing one. If
> memory serves me the plate is actually kept at 0VDC potential and the
> cathode is where the HV is applied. Audio input is fed via fiber optic to
> maintain isolation(?). I'm just going from a one-time explanation from 25
> years ago.
> Mod-U-Lator,
> Mike(y)/W3SLK
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