[Heathkit] foldback

Tue, 7 Oct 2003 18:48:59 -0700

Wow, what a great paper! I recently acquired the first amplifier I've ever
owned, an SB-200. I put in all the Harbach mods, but still didn't understand
much about it. Many of Rich's explanations of the design decisions and
performance considerations for the SB-220 apply to the SB-200. Thanks for
posting this link. I'm going to fire off an e-mail of appreciation to Rich
as well.

73, Dave, WA�TTN

> -----Original Message-----
> From: [email protected]
> [mailto:[email protected]]On Behalf Of Jim Brannigan
> Sent: Monday, October 06, 2003 2:38 PM
> To: Hotmail; [email protected]
> Subject: Re: [Heathkit] foldback
>
>
> This is Rich Measures' site.  There is a wealth of information on the
> SB-220.
> http://www.somis.org/sb220ci.html
>
> The SB-220 was designed when most exciters were tube based
> with a pi-network
> output.  The pi net output is able to match a wide range of
> loads and the
> input impedance of the amplifier was not a serious design
> consideration.
> Many Solid state exciters are not as forgiving and some
> attention to the
> amplifier input impedance is necessary.
>
> Jim
>
>
> ----- Original Message -----
> From: "Hotmail" <[email protected]>
> To: <[email protected]>
> Sent: Sunday, October 05, 2003 12:10
> Subject: [Heathkit] foldback
>
>
> > I have a great SB220 with the latest Harbauch mods that I installed.
> >
> > Question:
> >
> > My exciter (TS140S) folds back to 50 watts out on 10
> meters. How do I go
> about tuning the amplifier (input circuit I guess) to
> eliminate the foldback
> issue or is this normal?
> >
> > Thank you,
> >
> > Bruce
> >
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