I was asked by Michael Baker, K7DD, to provide the VF's for various
Flex-Weave Tm items. For the following reasons, there is no single answer
for this question without multiple factors being considered, however, the
"nominal" answer will certainly obtain optimal performance, short only
perhaps to "rocket science":
Propagation on bare, solid, or stranded copper or CCS (cop clad steel) wire
in a vacuum yields a VF of 100% or 1.00, the speed of light.
In air at sea level the nominal figure is 95%, used in dipole length
calculations.
In insulated wire, the figure varies around .90 - .95 - a good figure to use
in calculations such as EZNEC, etc, since any solution will be affected by
altitude, temperature, humidity, insulation thickness variance ,density, and
age, plus ultraviolet radiation and plain old dirt film.
It behooves most folks to use .95 in all wire antenna work, for the simple
reason that it is a lot easier to trim away a few inches than it is to add
on a few.
If you are using the PE insulated versions of ladder line, either stranded
or solid, 450 ohm having a few awg sizes, or the 300 ohm, over time we have
found that .91 VF is the number.
Some of the above info I learned from my good friend Press Jones over the
years, thus I bow to his wisdom.
Steve Davis, K1PEK
Davis RF Co.
www.DavisRF.com
978-369-1738
~ Davis RF Co., Div. of Orion Wire Co.,Inc.
Distribution to numerous industries, Andrew
Heliax; Times Microwave LMR; RFS Celwave and others.
Cable design engineering. RF Peripherals.
www.davisRF.com
Tel: 1-800-328-4773 (1-800-DAVIS RF) Tech'l: 1-978-369-
1738, Fax: 1-978-369-3484
~ DAVIS/ORION Marine Wire and Cable Co., Distribution and Design: UL/USCG
Marine Stds. Tel: 877-242-2253 Fax: 603-787-2221 (Direct tel to Steve
Davis: 978-369-1738 or Fax: 978-369-3484)
~Orion Wire Co., Inc., Design Engineers of Specialty/Custom Cable
Tel: 1-800-328-4773, 1-603-787-2200 Fax 1-603-787-2221,
email: j_stimson@davis-orionwiregroup.com
www.davisRF.com
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