Re: [Amps] fl2100F

[R.Measures <r@somis.org>]

On Dec 8, 2004, at 4:55 PM, carl seyersdahl wrote:

> I've had two answers on this and I now see what the problem is.!!!
>   There seems to have been numerous amps , using a pair of 572B's 
> (various
> mfrs.) None of these were perfect, BUT , some better than others.
>  I've repaired some of these amps, mostly SB 200's , and with a little
> "modern" application of parts, etc, most have worked quite well.!!!
>  However: The Heathkits mostly didn't have the 160 band, so I keep 
> wondering
> about it.!!!

Hello, Carl -- When the SB-200 and SB220 were introduced, it was not 
legal to use QRO at night on 160m because of LORAN, so it was deemed 
unnecessary to have 160m coverage on  amplifiers.

>    But I think the biggest problem is the HF end ( as in 10meters).!!!

Indeed.

>    Seems to me there were always those who could "invent" new mistakes 
> in
> these amps.!!!...
... ... ...
One problem was that HF amplifier designers used to ignore Feedback-C 
because it was insignificant at HF.  However, since the tubes we used 
(other than the 813) had significant gain at VHF, and  All  HF/MF 
amplifiers have a VHF resonance in their anode circuit, this turned out 
to be a mistake,

Richard L. Measures, AG6K, 805.386.3734.  www.somis.org

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