An SB-200 can be an absolute bear to tame in the input SWR region. There is
more at issue here than just the input tuned circuits (which by the way are Q
deficient - Mr. Measures will no doubt clue you on this. . . .). Check the
capacitors that are grounding the grid. . .does it look like they have too
much lead length?. . .They do. . .also look at the value. . .not enough. . .I
replaced them with a pair (at each point) of .01 1KV disks. This combined with
a variable cap across the 10 and 15M coils got a particularly nasty SB-200 to
put out full power and be driven with a cranky solid state rig. I also
"neutralized" it with a brass rod and a couple of wraps around the fil choke.
That seemed to stabilize it in 10M but I am not really sure . . .the dip was
better and power out coincided better with it. . .
Art
Tom Hellem wrote:
> Hi All:
> Can anyone tell me what would be the proper procedure for adjusting the
> input coils on an amp like the SB-200 or SB-220? Tried adjusting a SB-200
> last night by tuning the coil slugs while driving the amp to close to full
> output into a dummy load with a TS-440. Turning the coil slugs all the way
> in to all the way out made absolutely no improvement in the 3:1 SWR
> presented to the transmitter. Any help greatly appreciated.
>
> 73's
> Tom K0SN
>
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