Hi John & Carl,
I've got an old article describing the RCA BTA-5T which employs the harmonic
trap scheme posted on my webpage at:
http://wc6w.50webs.com/wc6wamps/index.html?fr522.html
73 & Good morning,
Marv WC6W
http://wc6w.50webs.com/
--- On Wed, 3/31/10, John Lyles <jtml@losalamos.com> wrote:
> From: John Lyles <jtml@losalamos.com>
> Subject: [Amps] Class F PA circuit tricks to improve efficiency
> To: amps@contesting.com, km1h@jeremy.mv.com
> Date: Wednesday, March 31, 2010, 2:46 PM
> This time i added a subject line,
> sorry.
>
> Carl, I didn't build the Tyler output modification, as the
> tube manufacturer in France doesn't recommend 'efficiency
> improvements' via plate current waveform modification.
> Although i did notice a copper slug
> in their own test cavity amplifier that was said to help
> minimize second harmonic power in the output. I am sticking
> to class AB2 - to B. I was referring to the effects on plate
> current waveshape (and measured
> DC to RF conversion efficiency) that MIGHT happen if a
> quarter wave stub was placed at the wrong place, distance
> from the plate to the stub. However, it would effect even
> harmonics and not odd ones, so it might
> have zero net effect. I hoped to hear someone's
> experimental evidence of this before I make big mechanical
> design changes.
>
> In some of the medium wave b'dcast transmitters with tubes,
> though, I've seen that circuit in use. The Collins 5 kW
> power rock did it. RCA had a nice app note on it, Power Tube
> Engineering Note IEN-4. They
> talked about the 5762/7C24 being overdriven with flat
> topped grid voltage in the BTA5U, and having third harmonic
> parallel resonant traps in the cathode and the plate leads
> to the tube.
> Its tricky to try and design these same equivalent
> resonators into a coaxial line circuit (a cavity). I can
> scan and email the app note, dated 1964.
>
> John
> K5PRO
>
> > Date: Wed, 31 Mar 2010 09:40:32 -0400
> > From: "Carl" <km1h@jeremy.mv.com>
> > Subject: Re: [Amps] gg feedthru power
> > To: <jtml@vla.com>,
> <amps@contesting.com>
>
> > Thats how I remember it also John but its been a long
> while since I read it!
> >
> > BTW, when you mentioned the Tyler circuit in that
> 500KW amp what efficiency
> > improvement were you getting? What class and how
> is it driven?
> >
> > Carl
> > KM1H
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