I have read that the presently available 300 ohm ladder line is
unsuitable to use at some amateur radio frequencies because of it's
construction and the losses caused by skin effect in the copper coated
steel construction. I have been using a Terminated Folded Dipole in a
flat top configuration as my HF antenna at home. Having recently
acquired an Icom AH-4 Antenna Coupler I am considering converting it
to a simple folded dipole, feeding it with 300 ohm ladder line to
match it's nominal impedance from the coupler. I know your sure that
there is a question in here someplace so is there better quality 300
ohm window line available that is entirely stranded copper in it's
construction?
--
Tom Horne, W3TDH

On Sun, 24 Oct 2010 20:23:29 -0700 (PDT), Tom Horne
wrote:

I have read that the presently available 300 ohm ladder line is
unsuitable to use at some amateur radio frequencies because of it's
construction and the losses caused by skin effect in the copper coated
steel construction.

Hi Tom,

You really have to question your judgment of the source of what you
are reading. The rationale of losses caused by "skin effect", and for
the very reason of it being copper is a perversion.

I have been using a Terminated Folded Dipole in a
flat top configuration as my HF antenna at home.

Revisiting this issue of line loss (however it was derived) in the
face of the loss in the terminating resistor of your antenna has got
your expectations inverted. Consider line loss in the tenths of dB to
1dB and the antenna loss easily double that worst figure (if not
triple or quadruple).

Having recently
acquired an Icom AH-4 Antenna Coupler I am considering converting it
to a simple folded dipole,

Folding it adds no virtue.

feeding it with 300 ohm ladder line to
match it's nominal impedance from the coupler.

If it has a nominal 300 Ohm Z, then use a conventional BalUn and coax
solution.

However, methinks you are going to treat this antenna as Z=300 at all
frequencies. No way.

I know your sure that
there is a question in here someplace so is there better quality 300
ohm window line available that is entirely stranded copper in it's
construction?

Consult the wireman.com.

73's
Richard Clark, KB7QHC

Tom Horne wrote in news:bc6994d1-be9a-45e6-8b56-
:

I have read that the presently available 300 ohm ladder line is
unsuitable to use at some amateur radio frequencies because of it's
construction and the losses caused by skin effect in the copper coated
steel construction. I have been using a Terminated Folded Dipole in a
flat top configuration as my HF antenna at home. Having recently
acquired an Icom AH-4 Antenna Coupler I am considering converting it
to a simple folded dipole, feeding it with 300 ohm ladder line to
match it's nominal impedance from the coupler. I know your sure that
there is a question in here someplace so is there better quality 300
ohm window line available that is entirely stranded copper in it's
construction?
--
Tom Horne, W3TDH

Tom, if you made a line of the dimensions of Wireman's 300 ohm line out
of HT steel, you would be looking at matched line loss at 80m in the
range 30 to 40dB / 100m, depending on the permeability of the steel wire.

If you made it out of copper, you would be looking at around 0.5dB.

The thing is that copper clad steel is somewhere in that range. If the
cladding is more than say, three skin depths in thickness, loss will be
almost identical to copper.Skin depth in copper is 35 microns, three
times that is 100 microns amongst friends.

The strands of 19 strand #18 are 200 microns in diameter.

I have no idea what the copper thickness is, but I suspect it is less
than 100 microns (as they would be pure copper in that case).

As Richard suggests, be perverse, ask the Wireman if he has measured loss
data for the line at 3.5MHz, not extrapolated data from higher frequency
measurements, but measured data.

I am not picking on the Wireman, Richard mentioned them, but I think the
same issue exists for all suppliers.

The only nominally 300 ohm line that is pure copper that I have seen is
TV ribbon, but that is probably not as good as you seek.

Think about the Wireman's 551 which is a single core CCS. If it is 30%
CCS, the cladding depth is about 7% IIRC, and that would make it 70
microns... might just scrape in with near copper performance on 80m.

The Rule of Thumb usually used is 2.5 to 3 times the skin depth gives
near copper performance.

Owen

On Oct 24, 10:23*pm, Tom Horne wrote:
I have read that the presently available 300 ohm ladder line is
unsuitable to use at some amateur radio frequencies because of it's
construction and the losses caused by skin effect in the copper coated
steel construction. *I have been using a Terminated Folded Dipole in a
flat top configuration as my HF antenna at home. *Having recently
acquired an Icom AH-4 Antenna Coupler I am considering converting it
to a simple folded dipole, *feeding it with 300 ohm ladder line to
match it's nominal impedance from the coupler. *I know your sure that
there is a question in here someplace so is there better quality 300
ohm window line available that is entirely stranded copper in it's
construction?
--
Tom Horne, W3TDH

For me, it's not the wire that is a problem. It's rain..
When dry, most all the 300 ohm lines are going to
be fairly low loss. Even with the cheap wire.
But get the line good and wet, and it all goes out the
window. For this reason, I would prefer a windowed
ladder type line for this, rather than 300 ohm.
It's less effected by rain.
Most ladder type lines will be in the 450 ohm range,
but that would vary with spacing of the conductors.
But that is not critical in your case.. 300, 450, 600
ohms, doesn't really matter too much..

On Oct 24, 10:23*pm, Tom Horne wrote:
I have read that the presently available 300 ohm ladder line is
unsuitable to use at some amateur radio frequencies because of it's
construction and the losses caused by skin effect in the copper coated
steel construction.

Where did you read that?
--
73, Cecil, w5dxp.com

On Oct 24, 8:23*pm, Tom Horne wrote:
I have read that the presently available 300 ohm ladder line is
unsuitable to use at some amateur radio frequencies because of it's
construction and the losses caused by skin effect in the copper coated
steel construction. *I have been using a Terminated Folded Dipole in a
flat top configuration as my HF antenna at home. *Having recently
acquired an Icom AH-4 Antenna Coupler I am considering converting it
to a simple folded dipole, *feeding it with 300 ohm ladder line to
match it's nominal impedance from the coupler. *I know your sure that
there is a question in here someplace so is there better quality 300
ohm window line available that is entirely stranded copper in it's
construction?
--
Tom Horne, W3TDH

Tom, what length of feed line are considering? How do you intend to
install it and support it from your shack to the antenna?

I have tried both 300 ohm TV type twin lead and ladder line. Both are
quickly affected by rain and snow. But more importantly is the wind
whipping the feed line and breaking it somewhere. About once per 6
month period I had to pull the whole antenna down and either replace
the feed line or find the break and repair it.

If you are able to secure the feed line with insulators every 10 feet
or so, the wind damage should be minimal.

A couple of years ago I made my own 600 ohm open wire feed line and
the wind is no longer a problem. The wind resistance is very low and
weather is only a problem when ice collects on the feed line.

IF you are interested, the 600 ohm feed line is #14 copper with
plastic rod insulators every 10 feet. The length from shack to antenna
is about 125 feet. Two poles support the feed line on its way and the
shack end is attached to a rope and pulley so I can adjust the
tension, or let the end down for maintenance.

Just some thoughts for you. Good luck, and don't be afraid to try
different schemes.

Paul, KD7HB
Central Oregon desert

On 10/25/10 12:50 PM, KD7HB wrote:

Just some thoughts for you. Good luck, and don't be afraid to try
different schemes.


300 ohm line is probably not the best choice if you want to use
non-coaxial feedline. Much better is real ladder line or window line.

And there are some serious misconceptions about window line too, so you
hav eto be careful of what you read.


Wes Stewart, N7WS wrote what is commonly cited as ladder line's fatal flaw:

http://users.triconet.org/wesandlinda/ladder_line.pdf

I suggest that you read it.


But the study in itself suffers from a fatal flaw. And it is actually
demonstrated in the article.

Stewart had difficulties in getting his ladder line completely wet. In
fact, the water created antibubbles on the surface of the line, and ran off.

Well now, how do we fix this? We apply wetting agent to the line, this
will cause the water to wet the entire surface, then measure the loss.

Anyone see the problem here? Last time I checked, there is no wetting
agent in rain. This is testing of artificially wetted window line,
nothing more, nothing less.

I have ladder line that has been up for 10 years now, and water still
beads up on it like it did when it was new. I'll not even add that it is
vertical, so there won't be as much water hitting it as when it comes
form a spray bottle - oh wait, I did mention it.....

The characteristics of polyethelene which is used to cover window line
in fact make it very difficult to be wetted. One might be able to
enforce wetting by sandblasting the line to roughen the surface, or oh
yeah, apply wetting agent.

That however makes the results of the experiment of equal value to
modifying coax in a detrimental way, then measuring some aspect, and
saying "all coax is like this". And why would ya do it anyway?

There are reasons to use ladder or window line, and there are reasons to
use coax. For example, at our club mountaintop station, we use
copperweld for the dipoles, properly hung on towers. There is a shrt run
of normal premium coax, just enough to lower the antennas for maintence
if needed, but the coax is switched to hardline coax for most of the run
into the shack. This is a good setup if you have lots of space, a goodly
number of towers, and monoband (or at least fan) antennas.

Now for the home QTH, I have some limited space, around a 100 feet. yet
I still want multi-band operation. So I'm looking at more limited choices.

Monoband dipoles are pretty much out of the question. Loaded multiband
dipoles? For all the ham bands? Maybe not so good. Fan dipoles? a pain,
and I'd have to start supporting the antenna on a messenger line.

So that ladder line or window line fed doublet is looking pretty darn
good about now. Rain or shine.

- 73 de Mike N3LI -

On Mon, 25 Oct 2010 14:44:20 -0400, Mike Coslo wrote:

Stewart had difficulties in getting his ladder line completely wet. In
fact, the water created antibubbles on the surface of the line, and ran off.

"Antibubbles?"

Well now, how do we fix this?

That the line was resistant to becoming "completely wet" would seem to
be a boon, not a problem, for its application.

We apply wetting agent to the line, this
will cause the water to wet the entire surface, then measure the loss.

Anyone see the problem here?

Most wetting agents are detergents (in fact the whole point of using a
detergent is for complete wetting).

Sources are obscured through other applications, but glimmers of
evidence suggest that adding a wetting agent will quadruple the
conductivity of water.

Last time I checked, there is no wetting
agent in rain. This is testing of artificially wetted window line,
nothing more, nothing less.

If adding a wetting agent is called for - in spite of its absence in
rain (for now until the new political alignment ****cans EPA) - it
will undoubtedly render the line as less than useful as would be
expected in either a wet or dry environment.

How did we get here?

73's
Richard Clark, KB7QHC

On 10/25/2010 6:42 AM, Cecil Moore wrote:
On Oct 24, 10:23 pm, Tom wrote:
I have read that the presently available 300 ohm ladder line is
unsuitable to use at some amateur radio frequencies because of it's
construction and the losses caused by skin effect in the copper coated
steel construction.

Where did you read that?
--
73, Cecil, w5dxp.com

He's right, Cecil. It's probably becoming an issue by 432, and I'd
really have to question anyone using it above 1296.

tom
K0TAR

On Oct 25, 9:16*pm, tom wrote:


He's right, Cecil. *It's probably becoming an issue by 432, and I'd
really have to question anyone using it above 1296.

tom
K0TAR

At 432 mhz, I had better luck with the 300 ohm TV line,
than I did using mediocre CATV cable and a balun.
This was feeding a UHF TV antenna that I used for ATV
on 70 cm. The 300 ohm line had the lower loss of the two.
Until it rained.. Then it was blackout time until it dried.
I have 300 ohm line feeding a 40 m dipole strung up in
the attic. It's an emergency antenna, and I use the 300
ohm line and a tuner to work any band 40-10m.
Being as it never gets wet, it works out pretty well.
300 ohm TV line is usually pretty good. Until it gets wet.
In the real world, I generally prefer coax. On the HF bands
it's about all I use. But the 70 cm ATV antenna was one
case where it paid to use the TV line vs coax. Or at
least the coax I had on hand.. Which was Beldon duo-shield
RG-6 type 75 ohm CATV cable.
Going by a gut hunch, I'd say the twin lead is probably
better than mediocre coax on 1296 mhz. You would need
some fairly high quality coax to equal the loss performance
of even cheap 300 ohm line on 1296 mhz. Or I would think
anyway, judging by it's use on 70 cm. I would think the
advantage would become more lopsided towards the 300 ohm
line, the higher in frequency you go.
I could look up the appx numbers in a book, but I'm too
lazy to get up out of my chair. :/