How to make a ladder feeder survive the wind?

I had better explain what a ladder feeder is first...

This ought to be in uk.radio.amateur, but it has been full of trolls for years and I will likely get more sensible suggestions here....

Its an antenna feeder cable, like a coax, but two separate parallel wires spaced apart around 1.5inches. The feeder you buy, is solid steel wire, copper plated, insulated by plastic, with the plastic insulation forming a pierced gap, rather like a ladder.

It appears out of the loft, between the roof tiles, it then goes up to feed a wire dipole. Imagine it coming out of the loft, the like a T where it meets the wire dipole. The ends of the wire dipole terminate at the front of the front garden and rear of the rear garden.

The problem is that the ladder feed keeps snapping too regularly, because it is very exposed and is in constant movement due to the wind. I replaced the commercial solid wire with 1.5mm flexible, spaced apart to form a ladder with several strips made from the plastic of milk bottles. Two small holes pierced either side, then feed the 1.5mm in then out and it stays put.

Use more substantial wire and it catches the wind more. Put twists in the ladder as it comes down and the wind causes it to try to rotate, alternatively winding itself up and un winding, putting more stress at the ends. I'm not sure whether it would be better taught, or more loose.

I should just like it to survive more than the present couple of years it presently lasts between replacement. It usually breaks, where it appears out between the tiles, down at the angle of the roof, then vertically up to the T. Adding metal around it is not an option, do to the RF on the feeder. I've tried various ways to try to relieve the stress, where it appears out from the tiles.

Reply to
Harry Bloomfield
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Phil L laid this down on his screen :

I'm no longer using the steel wire, it is 1.5mm stranded copper. Out from under the tiles is a must, the chimney is quite some distance away and would involve more ladder exposed to the wind/ more whipping action. I think the main issue is stress relieving as it emerges from the tiles, but everything I have so far tried, has just moved the point of breakage to the far end of the stress relief.

Even if it were attached to the chimney, it would come under stress where it left the last fixing on the chimney.

It has snapped again, needs to be repaired again - so the perfect time to do a rethink.

Reply to
Harry Bloomfield

I think you need to separate the "load carrying" part from the RF. Can you make your ladder out of polyester or nylon cord, tensioned where possible to reduce the amount of movement, and then run your conductors along it, tied every foot or so with cable ties, with a slight loop in the conductor. Rather like you would take a mains supply to a garage via an overhead straining wire.

Reply to
newshound

Open Reach seem to manage with their overhead cabling.

The insulated cable is fed through a loosely wound steel spring. The cumulative distortion gives a strong grip and transfers the cable tension to the spring which is then attached to the supporting pole.

Reply to
Tim Lamb

newshound explained :

That has promise. I could attach cord at the T where the ladder terminates, run both cord and ladder so far down and attached where it is exposed, then let it run free of any support back to the roof and under the tile. Fixing the support cord at the bottom, maybe near the gutter.

It enters under the tile on the usually more sheltered side of the house. The T is actually some 35 to 40 feet up by the way, but I made it so it can all be quickly lowered down to an easy working height.

Thanks!

Reply to
Harry Bloomfield

Rigidly fix a length of 1.5" diameter plastic rod or tube and attach the wires firmly to either side of that?

Reply to
Nightjar

The plastic you are using probably isn't UV stable which can't be helping. Replace the milk bottle plastic with something which is UV stable and you can get UV stable cable ties. For the wire you could try 'flexi-weave' ( the covered type), which is supposed to be UV stable. Plus the many strands make it, as the name suggests, very flexible.

The load carrying points are well made, adding some UV stable 'rope' (perhaps Kevlar) would help. Protect any chaffing points, perhaps with hose pipe ( I use it to protect coax and it seems to last a LONG time).

You should be able to guy it so it does twist too much, no more than a fraction of a turn I would think.

If you solve it, it would make a good article for RadCom.

73 Brian G8OSN
Reply to
Brian Reay

Run it inside a 2 inch plastic drainpipe?

Reply to
Denis McMahon

Class B licensees do not belong on HF.

Reply to
gareth

Quick explanation for those not of the Ham Radio / Amateur Radio persuasion.

To get a licence post-war, you had to satisfy your technical competence by passing the Radio Amateurs' Exam, a 3-hour traditional written paper, following which there were two classifications, class B where you could get a licence straight away because you were perceived as a technologist who who would pursue developments on VHF and higher frequenceies; and class A, the traditional licence for the short waves whereby you had to pass a further examination, a

12 words-per-minute Morse test.

There were many with the right moral fibre who wanted the short waves but lacked any interest in Morse and yet who tackled the Morse test and thus were prepared to put in the effort to get what they wanted.

Those class B licences who have now appeared on the short waves following the abolition of the Morse requirement were simply lacking the right moral fibre to tackle that test when it applied to them, and hence are held in derision by all self-respecting _REAL_ Radio Hams.

YMMV

Reply to
gareth

I was going to suggest much wider plastic that could be fixed in position down each side, but plastic pipe sounds better. All must be UVproofed of course, black gloss paint can do that.

NT

Reply to
tabbypurr

What's wrong with Co-ax?....

Reply to
tony sayer

Baluns.

Reply to
Huge

The trouble is that it needs to be in the open spaced away, or the impedance and losses tend to alter.

I suspect though that the steel wire is not doing his installation any favours as you note.

I suppose some plastic rope which is very taught with the feeder looped a bit between the attach points might break up the resonant vibrations caused by the wind on the flat shape.

Brian

Reply to
Brian-Gaff

tony sayer laid this down on his screen :

The ladder has to be a ladder, to feed into an auto-tuner. The auto-tuner then feeds onto coax. Balanced ladder line is a much more efficient feeder than coax, especial at HF.

Reply to
Harry Bloomfield

Harry Bloomfield used his keyboard to write :

Right guys, thanks for the suggestions. Here is what I have and what I am going to try....

1-------------S--------------T------------------------------------2

1 to 2 is around 50 metres, and is 2.5mm insulated flexible single core.

1 is the point of suspension at the front.

S is way above the apex of the house and the highest point of the wire. This is fixed to a vertical mast, the mast has an horizontal arm, with the wire spaced down from the far end of the arm. As such, the wire inverted V antenna, helps provide some stabilisation of the mast itself.

T is where the ladder meets and connects to the arms of the wire, the ladder feeder then just hangs down from there, then makes its way under a roof tile some 8 feet below the T.

Point S has a short length of tough plastic which is slightly curved and allows the actual wire antenna to easily move through it. That allows me to lower the T down, by just undoing at point 1, attaching a rope, and allowing the wire's own weight to lower point T down to an easy working height when standing on a flat roof at the rear of the house.

The actual active element, the wire from 1 to 2, never moves in the wind and is the original wire I installed decades ago. The only issues has been with the ladder feeder breaking - luckily I made it easy to access for replacement.

The strips of plastic milk bottle have also proven to be fine for many years, there has been no sign of any UV deterioration at all. It is also a good RF insulator.

What I am going to try, is attaching a cord at point T, I will then weave the cord in and out through the milk bottle insulators, most of the way down the ladder. The lower end of the cord I will then fix under the eaves. That should prevent the upper end of the ladder catching the wind, with only the final section of the ladder loose where it is sheltered and able to pass up under the tile from a much better angle.

The auto-tuner is around 3 feet inside the loft, from where the ladder feed passes under the tile. The tile is around 2/3rds the way down the slope of the roof, from the top, the apex.

The mast itself, supports a 2m/70cms/30Mhz antenna on top and a 2.4 Ghz link Yagi part way down.

2 is at the far end of the back garden.

The whole thing forms an inverted V.

Reply to
Harry Bloomfield

En el artículo , gareth escribió:

Self-respecting "real" hams such as your good self?

formatting link

Reply to
Mike Tomlinson

And what's wrong with impedance matching?...

Reply to
tony sayer

In article , Harry Bloomfield scribeth thus

Wonder why they don't use it for high power fM broadcast;?..

Reply to
tony sayer

That again...

A lot of us "failed class A" amateurs quite simply have no interest in pointless morse chatter, whether it be on HF, VHF, UHF, microwave or whatever. It's bad enough trying to coax your microwaves to travel through a piece of plumbing, without bothering about what they are carrying. :) My personal interest was originally RTTY, for which I simply didn't need morse. I was quite happy for a long time playing on VHF. I might even get on the air again once I retire. I'll be able to come and upset you on HF then. :)

Reply to
mick

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