Paul Burridge wrote:
Hi guys,

I've just been doing some calculations out of sheer curiosity. It
turns out that to make a tank circuit for 450Mhz (which isn't *that*
high a frequency by today's standards) would take 5pF || 25nF. These
are both *very* low values. 5pF is getting perilously close to being
seriously affected by circuit board stray capacitance and 25nF isn't
much better; little more than a couple of turns of wire, I guess.
What does one do in such circumstances? Should one be thinking in
terms of etching these values out of the PCB by the time one gets of
to these frequencies, or is it still acceptable to make them up out of
discrete components?


Don't you mean 5 pF || 25 nH? You could probably use a single turn or a
hairpin (1/2 turn) inductor and capacitor. It's quite workable at 450 MHz.


Leon
--
Leon Heller, G1HSM
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