Anyone know the velocity factor of JSC #1317 450 ohm line, 18 AWG?
Googling seems to give a variety of answers, and it's not posted at
the JSC site.

tnx,

Bob
k5qwg

On Sun, 04 Apr 2010 12:13:22 -0500, Bob wrote:

Anyone know the velocity factor of JSC #1317 450 ohm line, 18 AWG?

Hi Bob,

If you were to find a specification, it stands every chance of being
wrong. How much wrong is wholly dependant on your need for accuracy.

The answer to your question can only be effectively found at the bench
through measurements. Various reports from different reporters will
reveal a range of values because test conditions are also very
important and their variety give considerable sway. Some variation is
simply due to poor measurement technique. Some variation is a
function of production variation. Weather will contribute a
significant variation - more for ribbon line than open line.

At the end of the day, you can take an average of all such reports and
simply buy into the proposition that you have to tolerate a certain
level of indeterminacy. If you application demands precise accuracy,
then you might find you will never achieve it.

73's
Richard Clark, KB7QHC

Bob Inscribed thus:

Anyone know the velocity factor of JSC #1317 450 ohm line, 18 AWG?
Googling seems to give a variety of answers, and it's not posted at
the JSC site.

tnx,

Bob
k5qwg

You could get a sample and measure it !

--
Best Regards:
Baron.

Bob wrote in
:

Anyone know the velocity factor of JSC #1317 450 ohm line, 18 AWG?
Googling seems to give a variety of answers, and it's not posted at
the JSC site.

Wes, N7WS, measured some Wireman lines similar to that above. His
measurements indicated Zo quite different to nominal, and velocity factor
around 0.9.

For applications where velocity factor is important, eg the 'matching
section' of a G5RV, I suggest you measure the actual cable.

Wes's data is included in TLLC (http://www.vk1od.net/calc/tl/tllc.php).
Your cable has similar stranding to Wireman 551, but velocity factor will
depend on the detail of the dielectric extrusion and punching. If JSC is
the manufacturer, they may even be the source of Wireman lines, in which
case Wes's data may be directly applicable.

I have reservations about the adequacy of copper cladding on the cable
such as yours at the lower end of HF.

Owen

On Sun, 04 Apr 2010 20:46:21 GMT, Owen Duffy wrote:

Bob wrote in
:

Anyone know the velocity factor of JSC #1317 450 ohm line, 18 AWG?
Googling seems to give a variety of answers, and it's not posted at
the JSC site.

Wes, N7WS, measured some Wireman lines similar to that above. His
measurements indicated Zo quite different to nominal, and velocity factor
around 0.9.

For applications where velocity factor is important, eg the 'matching
section' of a G5RV, I suggest you measure the actual cable.

I'm plugging the velocity factor figure into Cecil's program for
optimum feedline lengths on a multiband dipole, IMAXMIN.EXE. Given the
approximate nature of this kind of feed, a ballpark figure is probably
okay.

Bob
k5qwg


Wes's data is included in TLLC (http://www.vk1od.net/calc/tl/tllc.php).
Your cable has similar stranding to Wireman 551, but velocity factor will
depend on the detail of the dielectric extrusion and punching. If JSC is
the manufacturer, they may even be the source of Wireman lines, in which
case Wes's data may be directly applicable.

I have reservations about the adequacy of copper cladding on the cable
such as yours at the lower end of HF.

Owen

Bob wrote in
:

....
I'm plugging the velocity factor figure into Cecil's program for
optimum feedline lengths on a multiband dipole, IMAXMIN.EXE. Given the
approximate nature of this kind of feed, a ballpark figure is probably
okay.

Bob,

Have you seen my article "Optimum length of ladder line" at
http://vk1od.net/blog/?p=949 ?

Owen

On 4 abr, 19:13, Bob wrote:
Anyone know the velocity factor of JSC #1317 450 ohm line, 18 AWG?
Googling seems to give a variety of answers, and it's not posted at
the JSC site.

tnx,

Bob
k5qwg

Hello Bob,

I used the ATLC program to calculate the properties of weird
transmission lines. It accepts arbitrary shaped dielectric material.
It outputs the line properties. When you run two simulations (with
window and without window), you can average them to find the velocity
factor of the ladder line.

The program can be retrieved from atlc.sourceforge.net (also Windows
versions). When you hit the tutorial button, you can check whether it
is worth to spend the time.

Looking to the picture of the line, most important for Zo is the ratio
(bare wire diameter)/(wire + insulation diameter) as E-field is
highest close to the conductors. For a ballpark calculation, I would
use VF = 0.92.

You can also determine the quarter wave resonance length by
measurement and calculate the velocity factor, but then you need
several meters at hand. When you really need VF with high accuracy,
measuring is the best option (around the frequency of interest). As
the separation of the wires is very small (w.r.t. length), it is
probably not necessary to correct for fringing at the open end.

Maybe the vendor cannot guarantee VF, because he receives material
from different sources.

Best regards and good luck with determining VF,


Wim
PA3DJS
www.tetech.nl
When using PM, remove abc before hitting the send button.

"Owen Duffy" wrote in message
...

I have reservations about the adequacy of copper cladding on the cable
such as yours at the lower end of HF.

Owen

I have often wondered the same thing. Mainly does the LMR400 center
conductor have enough copper over the center conductor for 1.8 to 7 MHz. I
don't use it at all as I just don't like the cladded cable.

"Ralph Mowery" wrote in
:


"Owen Duffy" wrote in message
...

I have reservations about the adequacy of copper cladding on the
cable such as yours at the lower end of HF.

Owen

I have often wondered the same thing. Mainly does the LMR400 center
conductor have enough copper over the center conductor for 1.8 to 7
MHz. I don't use it at all as I just don't like the cladded cable.




The issue is greater with the CCS conductors in ladder line, because the
strands are thinner in the first place, and the core is steel.

The effect of CCS inner conductor in some types of RG6 shows up as a
departure from the classic loss model at frequencies below 5MHz.

Owen

Owen

On Sun, 04 Apr 2010 20:38:35 +0100, Baron
wrote:

Bob Inscribed thus:

Anyone know the velocity factor of JSC #1317 450 ohm line, 18 AWG?
Googling seems to give a variety of answers, and it's not posted at
the JSC site.

tnx,

Bob
k5qwg

You could get a sample and measure it !

Well, I discarded that idea because I have no idea how.

But then, on a hunch, I checked the manual that came with my MFJ-269,
and sure enough, on page 34, it tells how to measure Velocity Factor,
utilizing the distance to fault mode. It'll take a day or so to
recharge the 269's batteries, and then I'll have at it.

Bob
k5qwg