GCR2 Preselector Coupling Capacitors
These graphs display the predicted shape of the preselector filter on various bands comparing the original 5pF coupling capacitor and and a capacitor chosen to optimize the coupling. The 5pF coupling capacitor was ideal for 80 meters, but on 160 meters the filter was being under-coupled and on the higher bands it was over-coupled. The 15 meter and 10 meter graphs with the 5pF capacitor at first glance don't look too bad; however, the peak that is shown is just one side of a broad double peak that is not shown on the graph. I now have a rotary switch installed so that I can choose between 40pF, 5pF, 1pF and 0.5pF (no capacitor, merely the stray switch capacitance). Thus, I can select the optimum coupling for each band.
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