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Tuesday, March 20, 2007

815 Xmtr Parts Subbing

As I search for parts, the topic of subbing parts has come up, particularly for C1 and C2. Miniture 140pf dual section variables are called out for both of these. In my junque box I fine slightly larger (physically) parts and, for C2, only a 100pf dual section variable. I can probably work around the 100pf problem by adding two fixed 50pf caps to L4, a 80JVL plug-in coil. The physical size increase appears to be OK for C2 but C1 is going to cramp the wiring around the oscillator stage. Can I shift C1 to tune L2 rather than L3? That reduces me to needing only a single section variable. Unfortunately is also means that I need to insolate "C1" from ground. The mounting starts to take up any space that I saved by changing to a single section cap. Looks like I'll stick with the parts I've found and just carefully lay out the oscillator stage in the space I have.

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