In a message dated 6/6/2006 12:04:30 P.M. Eastern Standard Time,
>From what Colin told me in a private email, it seems to me that the SB220
bandswitch is right on edge for the kW input power level, and too small at
1500 watts for safety. Really needs a bigger one, with a heavier indexing
mechanism. Now this isw ithout any parasitics, changing band instead of tuning
anything else. Then there's a problem for people who get arthritis in their
hands, and that really needs a bar type knob or even a door handle type
arrangement. I can't say that as a general rule, I particularly like round
switches - I prefer the bar types such as on the old TU units for the BC191.
They also have the advantage that you know immediately if you grab the
bandswitch. I believe that's called 'ergonomics'.
I was really never a Dentron lover and there has been many things said about
their amps, but I must admit they did use a much better band switch then
Heathkit did. They used pretty much the same switch on all their amps right
up to their powerhouse DTR 2000L whose band switch easily handles 1500 watts.
I think in the effort of keeping the SB-220 as small and compact as
possible they opted to use the switch that they used. I have seen quite a few
Supply amps (the new Dentrons) and I have really never seen a burned up band
switch like I have seen with Sb-220's. Most Dentrons did not have a tuned
input circuit but the radios of that era could handle that.
Remarkably, the Swan Mark I really was built like a tank and could easily
handle 2KW if it had the power supply to do so. B&W built an amp, the LPA-1
using an 850A and some really nice variable caps. But, they only ran a pair
of 813's. That amp could handle a bunch of power too if it had a formidable
PS and tube.
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