One more thing...if you are supporting ladder line with the recommended
twist, you could actually run the paracord through the holes in the
ladder line. I don't think it would have any impact on the performance
of the ladder line.
73
Dave, KD9VT
It's a Belville thing and you wouldn't understand.
------ Original Message ------
From: "Vic Lindgren" <g4byg@lindgren1.karoo.co.uk>
To: "jeremy maris" <jeremy@maris.plus.com>
Cc: topband@contesting.com; "Jim Garland" <4cx250b@miamioh.edu>
Sent: 1/8/2018 9:47:52 AM
Subject: Re: Topband: Supporting Ladder line
Thank you everyone for your contributions regarding my questions re
Ladder Line.
We will try a test run of the RG6U as suggested by Jeremy. Mainly
because we already have a source on site of the cable he suggested.
The WD1A telephone wire does not appear available in the UK.
You all appear to agree that it matters not whether supported
vertically or horizontally,as long as a twist is made to help maintain
both balance and wind survival. All great info folks.
Will let the group know our progress with the project shortly.
73
Vic
G4BYG (G6M)
On 7 Jan 2018, at 10:28, jeremy maris <jeremy@maris.plus.com> wrote:
Hi Vic,
I’ve done something similar to Jim with two paralleled runs of WD1A
for a bi-directional Beverage and it worked very well.
According to the specifications, WD1A is made up of two 0.85mm
diameter conductors separated by 0.85mm between the inner surface of
the conductors.
I took the effective diameter of two paralleled strands of WD1A to be
2mm. Two lines spaced apart by 50mm gives about 450 ohms impedance.
Paralleled strands of WD1A at 450/600 ohms are OK for RX but you want
to use the line for feeding QRO to a transmit antenna, so loss
matters.
I’ve considered using RG6U spaced apart by 150mm for 450 ohm TX
transmission line but think that I’d need too many poles to support it
with acceptable sag.
Aluminium wire or copperweld would be much better - it would be
lighter and hold more tension so less sag, fewer supports needed and
more consistent impedance.
Re horizontal versus vertical spacing, don’t think it will make much
difference on taught lines raised above head height.
73 Jeremy G3XDK / G4AQG
On 6 Jan 2018, at 21:05, Vic <g4byg@lindgren1.karoo.co.uk> wrote:
Thanks for that Jim,
Well we plan on using some on site "Shot Gun" coax (about 8 gauge
diam) as the ladder line conductors with a 6 inch spacing. Which on a
test length gave us around the 450 ohm impedance we require.
I dont know the diameter of that WD1a wire but suspect it is quite
small which would make home made 450 ohm line spacing very small
indeed.
Your method of supporting using the wood clamps sounds a good idea as
we were concerned about the plastic clamps breaking due to flexing
and UV deterioration.
If our conductors fail through the flexing then we may bite the
bullet and buy some Aluminium wire as Rik N6RK uses.
All useful info though and thanks again Jim.
73
On 06-Jan-18 20:38, Jim Garland wrote:
Vic, I've had nothing but bad luck in trying to support long
horizontal lengths of ladder line. In my case, I have two 720 ft
bidirectional beverages, which I initially made of heavy duty
commercial ladder line. I supported the line with wood 4"x4" posts,
spaced sixty feet apart, using the little plastic ladder line
clamps, sold in the US by DX Engineering.
After only a month or so, the plastic clamps broke apart because of
the repetitive flexing of the ladder line in breezes. I replaced the
clamps with wood clamps, screwed into the top of the posts. These
survived with no problem, but the ladder didn't. After six months or
so, I started having breaks in the line from the flexing, and after
spending two years repeatedly repairing the line, I gave up and
threw away all 1500 feet of the stuff.
Finally, I settled on WD1a military surplus field telephone wire,
available from many sources for about $50 USD in half mile lengths.
I use two parallel lengths of the wire, threaded through twin
ceramic insulators screwed into each 4x4 wood support (available
from a farm supply store), with a pulley at the far end to equalize
tension in the two lengths. In three years, it has worked perfectly,
with no problems at all.
I'm not disparaging ladder line (or the plastic clamps) at all. The
commercial stuff just isn't designed for long horizontal lengths.
73,
Jim W8ZR
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of
Vic
Sent: Saturday, January 06, 2018 01:17 PM
To: topband@contesting.com
Subject: Topband: Supporting Ladder line
Has anyone idea's of how to support a long (750 ft) length of home
made
450 ohm ladder line ?
Is it possible to use it supported from posts in a vertical
orientation or will that introduce
imbalance.
I would prefer not to have it supported horizontally due to added
cross arms being
required.
Have scoured internet sources but their appears little information
available on the subject.
I plan to feed a Marconi Tee Vertical (Hairpin Matching) with 9:1
transformers at each end
of the ladder line enabling use of 50 ohm coax at each end for
convenience.
73
Vic
G4BYG (G6M)
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