[Amps] Re: Amps Digest, Vol 12, Issue 35

[gw4dgu at blaenffos.org]

> **  I have yet to hear a Ham station on SSB who is getting 90% efficiency

Neither have I. But that's not the point of the discussion I was trying to
have. I was just trying to point-out that many hams are unaware of some of
the developments in transmitter design which have taken place since the
1950s, and that there are techniques being commonly used elsewhere which we
could use to our advantage.

As it happens, switching mode amplifiers (class-E, F, and beyond) can work
well to beyond the vhf region, but not as linear amplifiers. There's an
active group using them for CW PAs on the low bands - usually using cheap
general purpose power mosfets. Have a look at the Web.

But, it is entirely practicable to make an ssb transmitter with a switching
mode PA if you go about it the right way! There's a transmitter topology
(patented by the remarkable, and sadly late, Vlad Petrovic)  - polar loop
linearisation - which has been used in the past, and looks like it might be
making a comeback for cellphone base transmitters. A 90% efficient ssb
transmitter at HF could be a reality if someone had the time and backup to
design it.

Vy 73

Chris
GW4DGU