[Heath] SB-200 findings.

[pmarkavage at juno.com]

My comments below ***

On Thu, 05 Jan 2012 20:21:10 -0000 "Kenneth G. Gordon"
<kgordon2006 at frontier.com> writes:
> Over the past month or so, I have been experimenting with my SB-200 
> some more.
> 
>> What I found was that the input SWR did NOT change on any band 40
meters and higher, but it severely affected the input SWR on 80 meters,
requiring that  I change the 80 meter input network tuning capacitor from
470 pfd to 330 pfd to achieve a 1:1 SWR at 3750 Khz  (center of the
band).

*** I had diddle with the caps on 80, 15, and 10 meters on the input
network on both my SB-200's to get them anywhere near those particular
bands.
> 
> 2) One thing that has always bothered me about my SB-200 was that the
plate loading capacitor had to be "bottomed out" (i.e. fully meshed) for
maximum output at the low end of 80 meters, and I felt that it never was
really properly adjusted to peak in that portion of the band. (In fact,
this same thing was true about my first Heathkit transmitter, the DX-35).
 
Calculating the peak voltage at 2KW output into 50 ohms, I arrived at a
peak voltage of about 330. Therefore, just to check, I paralled C-27
(originally a 500 pfd 2KV capacitor, but mine had been replaced before I
got the amp with a 600 pfd 15KV door-knob) with a 500 pfd 1KV mica cap.
 
This brought the loading cap up to about 3 on the front-panel markings
and allowed me to be certain that the loading control was peaked
appropriately. Further experimentation and documentation will be done to
determine if this effects anything else, for instance, if I can still
peak the loading control at the HIGH end of 80 and/or 40.

*** Both my SB-200's worked exactly opposite on most of 80 meters. In
order to achieve full output, the loading control winds up at just about
minimum capacitance. 40 through 10 meters seem to be reasonable settings
of both plate and load controls.