[Amps] More pictures...

[Radio WC6W]

Hi David,
  The transformer is the least of the problems in that design adventure.

  In fact, if a (US) legal limit transmitter is designed with a 200V drain supply, then the load impedance is circa 50 ohms and a coaxial output transformer may be as simple as a piece of teflon coax with some ferrite around the outside.  The center conductor becomes the primary and the shield is the secondary with one end typically tied to ground.  The coax insulation will be plenty proof against the line potential.

73 & Good afternoon,
  Marv WC6W 

http://wc6w.50webs.com/


--- On Thu, 7/10/08, David Cutter <d.cutter at ntlworld.com> wrote:

> From: David Cutter <d.cutter at ntlworld.com>
> Subject: Re: [Amps] More pictures...
> To: amps at contesting.com
> Date: Thursday, July 10, 2008, 3:46 PM
> I was very pleased to read that you believe a way forward
> with a solid state 
> design is to use off line power, ie do the insulation in
> the rf stage.  My 
> ignorance with this is how the extra insulation might
> degrade transformer 
> performance.  Modern high voltage transistors from the
> likes of IXYS might 
> be the way forward, or perhaps cheap high voltage switching
> MOSFETs.
> 
> David
> G3UNA
> >
> > Well... I'm still on the lookout post for some
> legal limit SS PA design
> > that has advantages over the age-old and
> well-established ones, which
> > typically use 50V MOSFETs of ancient Motorola lineage,
> in class AB. The
> > advantages could be in obtaining high efficiency by
> running class E or
> > class F with envelope restoration, or at least in
> doing away with the
> > power supply by running directly off the line, and
> using low cost
> > transistors. If nobody comes up with something like
> this soon enough, I
> > guess I will! We need to innovate!
> >
> > But right now I'm playing with PICs rather than RF
> MOSFETs. There's less
> > to blow up with them. When I get fed up with those
> little cute digital
> > toys, I might return to the big and serious world of
> PA development! :-)
> >
> > Manfred.
> > 
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