[TowerTalk] Veloc Factors - wire + Lad line - from DAVIS RF Co.

[Steve Davis -Davis RF Co.]

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 at davis-orionwiregroup.com
 www.davisRF.com