On Sun, 21 Mar 2004 20:58:07 -0500, "Tam/WB2TT"
wrote:

Paul,

I probably should have included more details. A fellow I was working with
was trying to extract a clock signal from a synchronous data stream, and was
getting nowhere. We swept the frequency back and forth to be sure he was
tuned to resonance - he was. Changed the ceramic cap to mica, and everything
worked like a charm. We never analyzed why the ceramic did not work, but I
suspect it was because of the capacitance vs. applied voltage dependence. If
the cap had 6VDC on it, and he had a few mv of RF, I expect it would have
worked. Instead, he had 0 bias, and a couple of Volts p-p signal.

Yes, ceramics are *hopeless* for tuned circuits; I wouldn't trust the
black tipped ones, either. You can't beat silver mica but they're a
bit hard to find and expensive.


BTW, somebody mentioned powdered iron toroids. Sounds like a good idea.

Indeed. I'm looking into it.
--

The BBC: Licensed at public expense to spread lies.