[AMPS] SB221 7-band mod

[Dave Bernstein]

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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