RadioBanter - Copper tubing capacitors

Roy Lewallen wrote:
K7ITM wrote:
wrote:
I guess I'm learning a public lesson but I'm going to post this as a
wrapup.

I figured out the problem. My inch of wire appears to measure about
0.06 microhenries.

1/(2*Pi*sqrt(0.06microhenries*165picofarads) ~ 50MHz

73,
Dan
N3OX

Yeah, you discovered why they* suggest using an array of values of
bypass capacitors, even when using SMT capacitors with "zero" lead
length, to do a good job of bypassing a supply over a wide frequency
range. And why even in ham construction literature from the 1950s they
talk about keeping leads very short for good RF construction.
. . .

And just one of the many reasons I keep saying that good RF measurements
are much more difficult to make than most people realize.

Roy Lewallen, W7EL

As one who is dedicated to making equipment that enables making good RF
measurements, I say, "Amen, Brother Roy." One of the problems, if you
will, of modern test equipment is that it makes it LOOK like it's easy
to make good measurements, but you would be wise indeed to think
instead that the equipment operation is easier so that you can spend
your time making sure that your measurement setup is appropriate to the
task, and so that you can make measurements in multiple different ways
as a double-check or triple-check with less effort than you might have
used before to make one uncertain measurement.

Only slight topic drift: it's rather like trusting SPICE (or other
simulator) to give you the right answer without understanding either
SPICE's limitations or your model's limitations. Properly used, SPICE
is a great tool. Improperly used, it will give you some very bad
answers. Neither SPICE nor modern test equipment is a substitute for
using your head--but both can free you to use your head more
effectively and creatively.

Cheers,
Tom