[Amps] SB-220 Bandswitching

[W2RU - Bud Hippisley]

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 
battle".
.
> 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... :-) .

Bud, W2RU