Peter Chadwick wrote:
> In my innocence, something puzzles me. Is the indexing on the SB220
> bandswitch very weak, or are the capacitors very stiff?
In my opinion, the former is true -- on *my* SB-220, at least.
> I would have thought that the resistance to turning of the bandswitch would
> be sufficient to tell the operator that he (or she) was attempting to turn
> the wrong knob before it actually moved.
Peter, I think the problem is compounded by the fact that there's some
initial "stiction" when first trying to turn the capacitors. I just did
some experimenting in response to your posting, and I find the force
needed to get the capacitors to start moving is extremely similar to the
force needed to turn the bandswitch -- especially if the capacitors
haven't been turned recently.
Also, when operating a contest and/or suffering from lack of sleep,
there may be no rational reason for turning the wrong knob -- just a
"foggy" head doing dumb stuff. In my shack, the amplifiers are off to
the side so that I'm seldom looking in that direction "in the heat of
> What size is the bandswitch? Is it the one with centres about an inch and a
> quarter apart? If so, it's pretty marginal at 1 kW: the KW1000 amp from KW
> Electronics in the UK used that size switch, but had a phenolic shaft to get
> the voltage rating up.
Sorry -- can't help with answers to those questions. However, I *will*
say that my SB-220 seems to have too *little* bandswitch detent
resistance whereas my Amp Supply LK-550 has too *much*. In fact, I can
envision a time later in my life when arthritis or gradual infirmity
will make it impossible for me to change bands on the Amp Supply unless
I add some mechanical advantage to the present knob or wait for the home
health aide to arrive... :-) .
Amps mailing list