Using an SW-JV9039 8-pole 8-position ceramic switch from Surplus Sales of
Nebraska (402.346.4750) and toroid-based input circuits from the 3-500Z HF amp
design described in the 1996 ARRL handbook, my flea-market SB221 now handles
10m, 12m, and 17m, with a bandswitch position left over for 160m. Each switch
wafer provides two poles, but I used one pole per wafer for the two input
network poles since it reduced wire length. Two output poles -- one tapping
the tank inductor, the other switching in additional capacitance on 80M --
share a third wafer. While the switch is larger (and beefier, contact-wise)
than its predecessor, all was made to fit with minor drilling, filing, and
Plexiglas insulation.
The 8-pole switch is expensive. If I ever did this again, I'd be tempted to get
the cheaper 4-pole switch and put both input poles on the same wafer.
Dave
AA6YQ
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