Velocity Factors
 

I should like to know the velocity factors which occur on various
twin-balanced transmission lines. We have -

Open wire lines with infrequently spaced, flimsey spacers.

450-ohm ladder lines of various sorts.

300-ohm lines spaced with a thin continuous web.

130-ohm lines with two insulated wires stuck close together like twin
speaker cable.

75-ohm lines embedded in a solid eliptical-shaped polythene.

I daresay some of you have made measurements at one time or another.
The more data received the better. I can then take averages.

Thank you.
----
Reg, G4FGQ

Velocity Factors
 

Reg Edwards wrote:
I daresay some of you have made measurements at one time or another.
The more data received the better. I can then take averages.

I've only measured two of them, Reg. I measured "450" ohm
ladder-line VF at approximately 0.9 and "300" ohm ladder-
line at ~0.8. I was surprised since I assumed it would be
opposite those results.
--
73, Cecil http://www.qsl.net/w5dxp

Velocity Factors
 

"Cecil Moore" wrote
Reg Edwards wrote:
I daresay some of you have made measurements at one time or
another.
The more data received the better. I can then take averages.

I've only measured two of them, Reg. I measured "450" ohm
ladder-line VF at approximately 0.9 and "300" ohm ladder-
line at ~0.8. I was surprised since I assumed it would be
opposite those results.
--
73, Cecil http://www.qsl.net/w5dxp
==================================
Cec, the lower value for 300-ohm ladder line, compared with 450-ohm
ladder line, is what I would expect. Thanks for the figures.

It is the increase in capacitance between the two wires, due to the
permittivity of the insulation and because the wires are closer
together, which causes the decrease in velocity.
----
Reg.

Velocity Factors
 

On Wed, 5 Apr 2006 21:09:10 +0100, "Reg Edwards"
wrote:

I should like to know the velocity factors which occur on various
twin-balanced transmission lines. We have -

Open wire lines with infrequently spaced, flimsey spacers.

450-ohm ladder lines of various sorts.

http://k6mhe.com/n7ws/Ladder_Line.pdf

Velocity Factors
 

On Wed, 5 Apr 2006 21:09:10 +0100, "Reg Edwards"
wrote:

I should like to know the velocity factors which occur on various
twin-balanced transmission lines. We have -

Some of these are included in my line loss calculator at
http://www.vk1od.net/tl/tllce.php and are displayed along with
calculated results. See below...


Open wire lines with infrequently spaced, flimsey spacers.

450-ohm ladder lines of various sorts.

Wes' measurements of Wireman lines are shown as Wireman 551 .. 554.


300-ohm lines spaced with a thin continuous web.

I have measured TV ribbon of this type with a 7.5mm conductor spacing
and IIRC was around 82%. Similar line with puched out peices was
around 87% from memory. I you need, I can measure the punched type, I
am not sure if I have the plain ribbon around.


130-ohm lines with two insulated wires stuck close together like twin
speaker cable.

See ZIP 105 for K8ZOA's measurements of US Zip cord. See Australian
twin flex for my measurements of Oz figure 8 flex.


75-ohm lines embedded in a solid eliptical-shaped polythene.

See Belden 8210 and 8222 (from Belden specs).


I daresay some of you have made measurements at one time or another.
The more data received the better. I can then take averages.

I can see someone wanting to by 10m of "average cable"... but I think
I know what you mean!

Hope this helps.

Owen
--

Velocity Factors
 

Thanks, Wes, for the "Ladder line" pdf. I really enjoyed reading it.
Both factual and entertaining.

The impedances Zo of the nominal 450-ohm lines were all on the low
side. I wonder if this was due to the manufacturer's ignorance?

Did he use the usual ratio of wire-spacing to wire-diameter to deduce
Zo and forgot to multiply Zo by the VF to reduce Zo to the value he
actually achieved?

Then, it he ever measured Zo, he thought his measurements must be in
error and just carried on making the stuff.

Thanks for the data.
----
Reg.
==========================================


"Wes Stewart" wrote in message
...
On Wed, 5 Apr 2006 21:09:10 +0100, "Reg Edwards"
wrote:

I should like to know the velocity factors which occur on various
twin-balanced transmission lines. We have -

Open wire lines with infrequently spaced, flimsey spacers.

450-ohm ladder lines of various sorts.

http://k6mhe.com/n7ws/Ladder_Line.pdf

Velocity Factors
 

Has anyone ever measured the velocity factor of the twin feeder in
which the support for the wires is in the form of a plastic tube?

I would guess the VF is quite high. There is no insulation directly
between the wires.
----
Reg.

Velocity Factors
 

Some of the oval 300 ohm line, at least, was filled with PE foam. I
think this was intended to keep the water out.

Roy Lewallen, W7EL

Reg Edwards wrote:
Has anyone ever measured the velocity factor of the twin feeder in
which the support for the wires is in the form of a plastic tube?

I would guess the VF is quite high. There is no insulation directly
between the wires.
----
Reg.