>From time to time we've seen posts about how the SB-220's input
network is
>badly designed for 10 meters, and that results in lower output.
>
>Mine has a relatively high input SWR (ca. 1.8:1 on the part of 10
meters
>I'm interested in) and suffers from low 10m. output (ca. 800 watts at
>best), but even when I use the built-in tuner on my transceiver to
match
>the input perfectly, the output doesn't rise significantly. Why is
this?
>Is there really no alternative to taking the amp apart to get at the
input
>circuit and change component values?
>
Your experiment has just proved that the mismatch is between the input
network and the tubes, not on the transceiver side. 1.8:1 is very
acceptable
as I know of no transceiver that will begin to reduce power at that
level.
As long as the power out of the TX is not shutting back, you have done
all
you can on that side of the circuit. You don't need a perfect 1:1 vswr
on the
input; just low enough to allow the transceiver to deliver full power
across
a band.
The 800 watts seems in the ball park to me. Figure your efficiency and
let
us know what it is.
I doubt if you will gain any descernable signal strength on the RX end
by
perfectly matching the input network to the tubes, since you are so
close
already. If you cannot cover the whole band as it is, that's another
story.
GL!
(((73)))
Phil, K5PC
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