"Roy Lewallen" wrote in message
...
K7ITM wrote:
On Feb 5, 11:15 am, Dave99 wrote:
Hello,

Does anyone know if there's a way to determine the
velocity factor of
various metal tube types, diameters and gauges?

Also, on the same subject... Is there any reason why a
collinear
couldn't be constructed from metal tubing pieces, in the
same basic
method of a coax collinear?

Thanks for any help,

Dave

I'm not sure just what you mean by "the velocity factor"
of metal
tubes. Generally it's not the metal but the dielectric
that
determines velocity factor.

But for sure you can construct a collinear from metal
tubing pieces.
After all, coax is just a metal tube (which may be
braided, foil or
solid) surrounding a center conductor.

I suspect he means what length would be needed for a
resonant quarter or half wavelength. That's a function
only of the diameter. You can find graphs of a "shortening
factor" for dipoles or some such in numerous places such
as the _ARRL Antenna Book_. Or you can get that
information very quickly and easily with the free EZNEC
demo program from http://eznec.com or with any other
antenna modeling program.

Roy Lewallen, W7EL


---------------


But in the end, you still have to cut the tube to the
electrical performance desired. Measurements only get you
into the ball park. But I know that you knew that. G


Ed, NM2K