Cheap solid copper wire

D10 - mil-surplus field telephone wire. Comes as two separate wires, loosely twisted into a pair. Easily unravelled.

It's stranded, which is better. Solid core used outdoor in these lengths will break and it's a royal pain to find where.

Reply to
Andy Dingley
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I did wonder about that, because it's so quick and easy to lay down.

However, the previous occupants have thoughtfully left behind some "test samples", which show that in these ground conditions it will be rusting through within about 10 years... by which time it will have become impossible to rip up without ruining the entire area.

The advantage of copper wires is that they will last indefinitely, yet they can still be pulled out one by one (which I just did that at the old place).

Reply to
Ian White

How about Military Surplus telephone cable, D10

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it isn't stranded but is insulated with a PVC coat and nylon sheath so won't corrode for years. It is far tougher than most cables (3 steel/4copper strands per core) and usually sells for about GBP10 per

1km pack.

If single core is an absolute BDC/Micromark do a twin bell wire. Each conductor is single core PVC insulated 0.38mm x sec area in a figure of 8 configuration so fairly easy to separate. That is GBP4.80 per 100m ex VAT.

Reply to
Peter Parry

How did I guess...?

Ah, phased verticals (?)

Hmm, I've not come across that one before. It used to be quite common practice to use 7/36 stranded bare copper for (MF & HF) radio earth systems. Presumably you're suggesting that the inter-strand corrosion increases the RF resistance somehow - yet the current flow is longitudinal and surface corrosion of a single wire will also increase the RF resistance. Further explanation and scientific evidence would be of interest.

But surely almost all 'enamelled' wire these days is solderable polyurethane insulated and won't need scraping. It needs a hot iron (or flame) for soldering and emits toxic fumes (toluene di-isocyanate) - but I'm sure you know that already.

Interesting. When I used to operate on 160m (a long time ago) I used to dig a narrow slit and push the wire down a few inches.

The trouble is that to a wire supplier 1 km is a small quantity and doesn't give you much buying power. Nevertheless you should be able to buy bare or tinned wire in 500m reels at much better prices than in the RS or Farnell catalogues. I reckon you're after roughly 10 kg of copper in total.

You can get 6491X PVC insulated conduit wire in solid (single-strand) up to 2.5 mm^2. (But PVC is a poor dielectric and might also add significant RF loss.)

YIK, but it did meet the "cheap" part of the specification.

Reply to
Andy Wade

(typo: isn't solid / is stranded)

Thank you, both. With that kind of extra-tough insulation, stranded wire would be just fine.

A quick Google found Ramco in Skegness selling D10 on eBay at GBP40 for

800m (though a friend in the area could no doubt get it for less). Anyone else you know of... a bit closer to PP's GBP10/km mark, maybe?

Getting warmer! Told you this was the right place to ask :-)

Reply to
Ian White

electrical

enough

simply

half-inch

current it

strength,

allows

Some options:

  1. go with bare copper 1.5mm wire
  2. I guess copper coated steel would be cheaper and tougher, but have no idea where or if its available.
  3. Use enamelled, very cheap indeed, and a dremel type tool with a rotary wire brush for superfast stripping.
  4. Use assorted scrap. It then doesnt matter if its

- insulated

- T&E

- etc Just use them as they are, dont strip, dont separate the wires in T&E etc.

NT

Reply to
bigcat

Walts just so much fun though ;-)))

Reply to
Badger

The only fun thing about Walt would be watching him burn to death.

Reply to
Huge

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Ormiston Wire (who don't seem to have a web site) will sell you the wire cut to length and straightened. Even if you want to do the work yourself, that will still probably be the cheapest sort of place to buy from.

Colin Bignell

Reply to
nightjar

Sounds about right for a vertical on most amateur bands below 14MHz. there is an LF band noe about 137khz I think, and an mf one at about 1.9MHz.

Reply to
<me9

Want one for when I next get on 160m.

Reply to
<me9

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wouldn't it be easier to just phone them?

Reply to
Steve Walker

Would you need to remove it? Just bung some more down... The lower Z of the new stuff shorting out any higher Z bits in the old.

Reply to
Dave Liquorice

Thats what I call an earth mat Ian!

Peter Crosland

Reply to
Peter Crosland

Far too quick and painless.

Peter Crosland

Reply to
Peter Crosland

That's what I paid for what I think was 1km, from Anchor surplus in Ripley / Nottingham.

Reply to
Andy Dingley

And what happens after another 10 years? I would really not like to leave the land in that condition.

Just think - in the next life, I might be sent back as a mole.

Or you might :-)

Reply to
Ian White

That's right. Four verticals at the corners of a 10m square, phased together to create a directional beam that is instantly switchable in any of eight directions.

Part of the fun of playing with aerials is that it's a mixture of electronic engineering and DIY (though I must admit there's not a lot of scope for paperhanging).

Sorry, this is getting a bit OT, but it might be interesting...

Something called the 'skin effect' makes radio-frequency (RF) currents flow only on the outside skin of a conductor. Skin depth decreases with frequency (square root of). No current flows within the wire, so its current-carrying cross-sectional area is much smaller than its physical cross-section. Therefore its effective resistance is higher at RF than it is at DC or 50Hz.

The difference between solid wire and stranded is that the current has to hop from strand to strand in order to flow straight down the wire, because the lay of the strands is slightly spiral. There is only a small mechanical force holding adjacent strands together, so the contact is never very good and so the RF resistance is just a little bit higher than for the same-size solid wire.

Exactly the same happens in braid, as used for the outer shielding of coaxial cables. Because the lay of the strands is more diagonal, more hopping is required so the RF resistance is a little bit higher still.

Now add a thin layer of surface corrosion, which has a much higher resistivity than metal. In the solid wire, the current simply pulls back into the metal skin beneath, so the RF resistance is almost as low as before. But in the stranded wire, the individual strands are forced apart and the RF resistance can become a lot higher.

The most dramatic demonstration is what happens when the outer plastic jacket of a coaxial cable is cut and rainwater gets in. When the braid corrodes, the strands are forced apart and the RF resistance increases dramatically. The braid also wicks the water down along the rest of the cable run. If this has happened, the only solution is to replace the whole length - it's shot.

This effect would be nothing like so severe for my earth mat application; but given the choice of solid or stranded wire, it's something I'd rather avoid. However, the D10 telephone wire might change my mind, because the insulation is extra-strong and would protect the wire much better.

That only applies to 'instrument' wire on small reels. The main source of enamelled wire on big reels still tends to be from motor winding shops, and they often use a more modern version of the brown enamel which is double-coated, temperature-resistant and tough as old boots. (But the Dremel trick is duly noted - thank you.)

Thanks for the correction - I'd thought it was all stranded, so that is yet another possibility. No problem about the PVC, because the main RF losses are in the ground that it's touching.

I may well do that for the eight "busbar" wires to which all the others are soldered. For the other 120 wires, I'd prefer less preparation work if at all possible.

Reply to
Ian White

The bloke's reputation precedes him, apparently.

BTW, uk.radio.amateur is a cesspit. The OP *is* better off asking here.

Reply to
Huge

nightjar or Ormiston Wire (who don't seem to have a web site)

Yes they do -

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which I mentioned earlier in this thread.

Reply to
Andy Wade

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