[Heath] SB-200 loading question.

[Ken Winterling]

Ken,

How does it respond on a 50 ohm dummy load?  It is best to perform all
testing on a dummy load so as to eliminate the antenna and associated
cable(s) as a variable.

Ken
WA2LBI

On Thu, Dec 8, 2016 at 19:37 Kenneth G. Gordon <kgordon2006 at frontier.com>
wrote:

>
> I am somewhat confused here and I hope someone can help:
>
>
> I am refurbishing an SB-200 for a friend.
>
>
> In this amp, C-27, the fixed 500 pfd 2 KV mica capacitor which is switched
> in parallel with
>
> the loading capacitor C-28A/B on 80 meters where additional loading
> capacitance is
>
> needed, especially on the low end of the band, had been replaced with a
> 525 pfd "door
>
> knob" capacitor capable of at least 5 KV. This "door knob" is a large one
> and I think it is
>
> actually either a 10KV or 25KV job.
>
>
> It checks out with my cap meter perfectly.
>
>
> While using this amp, with new finals, on the low end of 80 meters, I "run
> out" of loading
>
> capacitor before achieving full load. I.e., the loading capacitor is up
> against the full-capacitance stop.
>
>
> The antenna is being fed through a home-brew antenna coupler, and the SWR
> between the
>
> amplifier and the coupler is 1:1.
>
>
> I then paralleled that "door-knob" capacitor with a 500 pfd 2KV mica, and
> STILL run out of
>
> loading capacitance on the low end of 80 meters.
>
>
> The amp works perfectly and properly on all other bands and frequencies.
>
>
> I then checked the bandswitch and every connection in the output tank and
> everything is
>
> working exactly correctly.
>
>
> I then tried a different set of new finals, and got the same result.
>
>
> Anyone here have a clue as to what is going on?
>
>
> Even with the amp acting this way, I can easily achieve at least 600 watts
> output with
>
> around 50 watts of drive, and I am happy with that, but this still does
> not seem right to me.
>
>
>
> Ken W7EKB
>
>
> --

Ken
WA2LBI

Sent from one of my mobile devices
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