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

[R.Measures]

>> **  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.
>
**  The sticky wicket with Class-E  for Ham applications could well be 
the requirement for wide frequency coverage.   However, since some Hams 
already use electron-tube monobander amps, maybe they would be the first 
to switch to switching-mode monoband amplifiers?   
>
cheers, Chris