- Joined May 15, 2010
I believe the ones Sam posted are ceramic. I purchased a big pack like that and many didn't work or would only turn so many times before being damaged. If your making radios spend a little extra for a high quality trimmer because these little ones are a pain.Wow, that's a good deal. Do you know if that type is suitable for RF? Some of the circuits I want to build specify "ceramic trimmer", which I'm not sure those plastic encased ones are?
Hmm maybe mine are plastic.. they were marketed as ceramic and now you guessed it no more listing!Nope, definitely plastic! Not for a power circuit! And NO SPECIFICATIONS or PDF! Strictly for playing around with at home. Not a bad little kit to have stuck away to play around with filters.
Any reason not to opt for a homemade foil capacitor?They were all ceramic until they "invented" injection moldable plastic. They might all be plastic now? When you start messing around with RLC circuits it is nice to invest in a good LCR meter although the cheap chinesium "do all" tester will at least get you into the ballpark if not right on home plate. Less than 20 pico takes a very good meter.
I made one with a piece of 8 1/2 x 11 paper as insulator with two pieces of foil the same size. Worked ok as long as it isn't bumped. You could also try long pieces of wire as plates for some interesting synthesizer effects.Size?
That's the main problem trying to measure picofarads even after zeroing the relative reference. You can zero out the wiring connections but your body's movement can skew the reading unless you distance yourself. Also, tweaking an adjustable trimmer cap has the same problems. One reason why Farraday cages are used for RF. Not just to prevent RF from escaping but also to prevent outside sources from interfering.I've tuned by moving my hand near a wire as well.
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by Aaron Carman
by Jake Hertz