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 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. :/

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, if he using "an Icom AH-4 Antenna Coupler" on 1296, he's got more
problems than 300 ohm twinlead. :-)
--
73, Cecil, w5dxp.com

On 10/27/2010 6:26 AM, Cecil Moore wrote:
On Oct 25, 9:16 pm, 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, if he using "an Icom AH-4 Antenna Coupler" on 1296, he's got more
problems than 300 ohm twinlead. :-)
--
73, Cecil, w5dxp.com

Can you say "facetious"? I bet you can. (Apologies to Mr. Rogers)

tom
K0TAR

On Oct 27, 6:38*pm, tom wrote:
Tom, if he using "an Icom AH-4 Antenna Coupler" on 1296, he's got more
problems than 300 ohm twinlead. :-)

Can you say "facetious"?

The happyface-tious above should answer that question.
--
73, Cecil, w5dxp.com