Velocity factor and impedance of ladder line
 

What is LIKELY to be the true impedance and velocity factor of 450 ohm
window 18AWG solid polyethylene ladder line? I see everything from .85 to
..95 and 375 to 440. Most seem to think it's around .865 and 390 ohms. Is
this close enough? I have no way of actually measuring it.
BTW, same as what the Wireman sells.

Sorry for asking a question that's been asked before, but it does have many
ambiguous answers and I'm not sure what it really is. I'm using for a
matching stub and need to fairly close.

Thanks...

--

***** Jim Leder *****
IBM retiree since 1999
http://home.fuse.net/k8cxm

Jim:

I have no information to answer your two questions numerically, but I do want to point out the following: Both the
impedance and velocity factor will be different in the solid sections and in the windows. So, if you need great
accuracy, good luck!

--
Crazy George
The attglobal.net address is a SPAM trap. Please change that part to: attdotbiz properly formatted.
"Jim Leder" wrote in message ...
What is LIKELY to be the true impedance and velocity factor of 450 ohm
window 18AWG solid polyethylene ladder line? I see everything from .85 to
.95 and 375 to 440. Most seem to think it's around .865 and 390 ohms. Is
this close enough? I have no way of actually measuring it.
BTW, same as what the Wireman sells.

Sorry for asking a question that's been asked before, but it does have many
ambiguous answers and I'm not sure what it really is. I'm using for a
matching stub and need to fairly close.

Thanks...

--

***** Jim Leder *****
IBM retiree since 1999
http://home.fuse.net/k8cxm

Jim Leder wrote:
Most seem to think it's around .865 and 390 ohms.

That's fairly close to what I measured for the #14 stranded.
Depending upon the amount of insulation, which varies
from run to run, the VF can be higher or lower.

I'm using for a matching stub and need to fairly close.

Cut&Try. Make it too long and chop until perfect.
--
73, Cecil http://www.qsl.net/w5dxp


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On Thu, 24 Feb 2005 19:14:25 -0500, "Jim Leder"
wrote:

What is LIKELY to be the true impedance and velocity factor of 450 ohm
window 18AWG solid polyethylene ladder line? I see everything from .85 to
.95 and 375 to 440. Most seem to think it's around .865 and 390 ohms. Is
this close enough? I have no way of actually measuring it.
BTW, same as what the Wireman sells.

Sorry for asking a question that's been asked before, but it does have many
ambiguous answers and I'm not sure what it really is. I'm using for a
matching stub and need to fairly close.

http://users.triconet.org/wesandlinda/ladder.htm

You say, "I have no way of actually measuring it." But I wonder about
that. Certainly it's not too difficult to find the velocity factor
with the simplest of equipment, and with a bit of creativity, you
should be able to figure out the impedance as well. In any event, it's
pretty common to make at least minor tweaks on matching stubs to get
them to do the intended job. Will you have any way to know when it's
doing its job properly? That in itself may be all the measurement you
need.

Cheers,
Tom