I'm looking for about 1km of thin-ish solid copper wire, as cheap as
possible.

1. Solid, not stranded
2. To be used as single wires, in lengths of typically 10m
3. Could be insulated or bare, tinned or not; but not enamelled (unless
the price was very, very right)
4. Strong enough to cope with being laid on the ground outdoors, and
then generally trodden on and mowed over
5. Thin enough to be cheap.

About 1.0-1.5mm diameter would probably be fine.

In the catalogues, the best options so far seem to be multi-core cables
of some kind. 12-core telephone cable is a reasonable price from TLC,
though it's thinner than I'd prefer, and I'd rather not to have to strip
and untwist it to get to the individual wires.

Solid twin bell wire from TLC would be fine, but significantly dearer
per 100m of single wire. (Screwfix bell wire is stranded, so no use for
this.)

Any better ideas from you intrepid bargain hunters, please?



--
Ian White

Ian White wrote:
I'm looking for about 1km of thin-ish solid copper wire, as cheap as
possible.
1. Solid, not stranded
2. To be used as single wires, in lengths of typically 10m
3. Could be insulated or bare, tinned or not; but not enamelled (unless
the price was very, very right)
4. Strong enough to cope with being laid on the ground outdoors, and
then generally trodden on and mowed over
5. Thin enough to be cheap.
About 1.0-1.5mm diameter would probably be fine.

As it doesn't have to be insulated, if it didn't have to be copper, I'd
suggest looking at fencing wire.

If it could be stranded I'd suggest looking at electric fence wire.

Owain

In article ,
Ian White wrote:
I'm looking for about 1km of thin-ish solid copper wire, as cheap as
possible.

1. Solid, not stranded
2. To be used as single wires, in lengths of typically 10m
3. Could be insulated or bare, tinned or not; but not enamelled (unless
the price was very, very right)
4. Strong enough to cope with being laid on the ground outdoors, and
then generally trodden on and mowed over
5. Thin enough to be cheap.

About 1.0-1.5mm diameter would probably be fine.

In the catalogues, the best options so far seem to be multi-core cables
of some kind. 12-core telephone cable is a reasonable price from TLC,
though it's thinner than I'd prefer, and I'd rather not to have to strip
and untwist it to get to the individual wires.

Solid twin bell wire from TLC would be fine, but significantly dearer
per 100m of single wire. (Screwfix bell wire is stranded, so no use for
this.)

Any better ideas from you intrepid bargain hunters, please?

You need to specify either cross sectional area, SWG, or what current it
has to carry.

Single core insulated for electronic stuff is available from RS Components
etc. Go up to normal mains - ie 1mm/sq and above and you'll get it at any
electrical wholesaler. Single core is used in conduit, etc.

--
*Many hamsters only blink one eye at a time *

Dave Plowman London SW
To e-mail, change noise into sound.

On Fri, 20 May 2005 22:41:50 +0100, Ian White wrote:

About 1.0-1.5mm diameter would probably be fine.

A quick look on RS shows 500m of 1/0.8mm at =A326.72 + VAT code 183-9231=

for white also available in blue or brown.

--
Cheers
Dave. pam is missing e-mail

Dave Liquorice wrote:

About 1.0-1.5mm diameter would probably be fine.


A quick look on RS shows 500m of 1/0.8mm at £26.72 + VAT code 183-9231
for white also available in blue or brown.


I don't see how any thin wire can satisfy "Strong enough to cope with
being laid on the ground outdoors, and then generally trodden on and
mowed over". I don't think even CAT5 or T&E can withstand these
conditions long term.


--
Grunff

Ian White wrote:

I'm looking for about 1km of thin-ish solid copper wire

It might help if you gave a hint *what* you want to use it for, from
your description hopefully it wouldn't be for carrying 240v ...

Ian White wrote:

I'm looking for about 1km of thin-ish solid copper wire, as cheap as
possible.

1. Solid, not stranded
2. To be used as single wires, in lengths of typically 10m
3. Could be insulated or bare, tinned or not; but not enamelled (unless
the price was very, very right)
4. Strong enough to cope with being laid on the ground outdoors, and
then generally trodden on and mowed over
5. Thin enough to be cheap.

RF groundplane: earth mat or radial system for a vertical radiator? Try
http://www.ormiston-wire.co.uk/ or G. Barmaper in Stanmore. Or get some
7-strand conduit wire (say 10 or 16 mm^2) and strip out the strands.

73
--
Andy

In article , Grunff
writes
Dave Liquorice wrote:

About 1.0-1.5mm diameter would probably be fine.


A quick look on RS shows 500m of 1/0.8mm at £26.72 + VAT code 183-9231
for white also available in blue or brown.


I don't see how any thin wire can satisfy "Strong enough to cope with
being laid on the ground outdoors, and then generally trodden on and
mowed over". I don't think even CAT5 or T&E can withstand these
conditions long term.



What?,, Do you want to use it for?.....
--
Tony Sayer

Thanks very much for the replies so far. I really do appreciate how you
lot get your teeth into an unusual problem!

But I misjudged the amount of detail that people might need in order to
give a helpful reply. My apologies for that - I was trying to spare you
all "the full half-hour". Well, here it comes...

This is a rather unusual application, and many of the normal electrical
wiring requirements do not apply.

I'm looking for about 1km of thin-ish solid copper wire, as cheap as
possible.

Yes, Andy, it is to make a ground mat for a radio aerial... well, four
aerials actually! This requires the wires to be laid out in a fairly
precise pattern of four radial fans, and the ends soldered to bare
copper "busbars".

BTDT before, but only on a smaller scale requiring much less wire. This
time I'm doing it at a new location and on a much bigger scale.

The amount of wire required - literally more than a kilometre - means
that (a) I'll have to buy it, and (b) paying the odd few pence more per
metre will add up to serious money.

The number of separate lengths of wires involved - approaching 200 -
means I have to think about easy "mass production" techniques. Many of
the things you wouldn't hesitate to do for a few tens of metres are
simply not on at the kilometre scale. Wire's too long; life's too short.


1. Solid, not stranded

That is an absolute requirement - please take my word for it. (At radio
frequencies, the resistance of stranded wire becomes much higher when
the strands corrode, as they inevitably will over the years. Solid wire
is much less affected.)

2. To be used as single wires, in lengths of typically 10m
3. Could be insulated or bare, tinned or not;

From the performance point of view, it makes no difference whether the
wire is insulated or not (see, I told you this was unusual).

but not enamelled (unless
the price was very, very right)

BTDT - enamelled is a pain to scrape and connect, especially when doing
it about 200 times, outdoors at ground level.

4. Strong enough to cope with being laid on the ground outdoors, and
then generally trodden on and mowed over
About 1.0-1.5mm diameter would probably be fine.


Sorry, Grunff, I may have misled you by not specifying the kind of
surface. On grassy land, 1.5mm diameter copper is plenty strong enough
for the basic radial wires - strong enough to trip someone up, and it
will even stop a rotary mower (it cuts the wire, but the wire wins in
the end, by strangulation).

The trick when laying wires on grass is to mow the grass very short
first. Then lay the wires along the ground, heel down any sticking-up
loops, or pin them down with thicker wire 'staples'... and then simply
leave them. Just carry on mowing a bit higher than usual (which is where
you find any loops that you didn't pin down properly) and within a year
the wires will have disappeared under the root mat. It's quite
remarkable. Within two years, you'll even have to search for half-inch
cables.


5. Thin enough to be cheap.

As I said, on this scale the price per metre of wire really does matter
- especially bearing in mind it's only for a hobby. Each extra penny per
metre becomes another 10 quid on the total cost.

Dave said:
You need to specify either cross sectional area, SWG, or what current it
has to carry.

I'd hoped to get away without having to go into details, Dave... but
judging by some of the questions we get on here, you were quite right to
ask :-)

For this unusual application, most of the normal electrical wiring
factors don't matter at all. It all comes down to mechanical strength,
and price.


Single core insulated for electronic stuff is available from RS Components
etc. Go up to normal mains - ie 1mm/sq and above and you'll get it at any
electrical wholesaler.

If buying at normal catalogue prices, I'd rather spend all the money on
copper than on insulation that isn't needed. However, plain bare solid
copper seems to be the province of "instrument wire" suppliers, and is
sold at a huge premium compared with the copper content of say T&E.

Single core is used in conduit, etc.

Stranded, alas. That is the one definite no-no for this particular
application.

Andy said:
Or get some 7-strand conduit wire (say 10 or 16 mm^2) and strip out
the strands.

Because of the total length of wire involved, I'm afraid that would be
far too labour-intensive. The same would apply to options such as
stripping down scrap T&E. It's got to be some kind of wire that allows
an easy "mass production" technique.

Tricky... but I really do appreciate your help and good thinking.


--
Ian White

In article ,
Ian White wrote:
[snip]
BTDT - enamelled is a pain to scrape and connect, especially when
doing it about 200 times, outdoors at ground level.

There is a low-temperature enamel which melts at
(high) soldering temperatures. Tradename 'Quikstrip'
afair, and is a light salmon-pink coloured enamel.
Most of the en-cu in RS is Quikstrip I think.

--
Tony Williams.

In article ,
Ian White wrote:
Single core is used in conduit, etc.

Stranded, alas. That is the one definite no-no for this particular
application.

All the 1 - 1.5mm singles I've seen are solid core. 2.5mm may be either
solid or stranded.

--
*If horrific means to make horrible, does terrific mean to make terrible?

Dave Plowman London SW
To e-mail, change noise into sound.

Ian White wrote:

Yes, Andy, it is to make a ground mat for a radio aerial...

I did wonder ....

BTDT - enamelled is a pain to scrape and connect

Dip the end in meths and burn it off? still a bit of messy to clean if
you're neeed to solder (and repeat 200 times)

tony sayer wrote:

What?,, Do you want to use it for?.....


I don't, I'm not the OP!


--
Grunff

In article , Ian White
writes
Thanks very much for the replies so far. I really do appreciate how you
lot get your teeth into an unusual problem!

But I misjudged the amount of detail that people might need in order to
give a helpful reply. My apologies for that - I was trying to spare you
all "the full half-hour". Well, here it comes...

This is a rather unusual application, and many of the normal electrical
wiring requirements do not apply.

I'm looking for about 1km of thin-ish solid copper wire, as cheap as
possible.

Yes, Andy, it is to make a ground mat for a radio aerial... well, four
aerials actually! This requires the wires to be laid out in a fairly
precise pattern of four radial fans, and the ends soldered to bare
copper "busbars".

You should be over on uk.tech.broadcast for that sort of thing:!...

BTDT before, but only on a smaller scale requiring much less wire. This
time I'm doing it at a new location and on a much bigger scale.

The amount of wire required - literally more than a kilometre - means
that (a) I'll have to buy it, and (b) paying the odd few pence more per
metre will add up to serious money.

Building some medium powered MF station?.......
--
Tony Sayer

Bancom Communications Ltd U.K. Tel+44 1223 566577 Fax+44 1223 566588

P.O. Box 280, Cambridge, England, CB2 2DY E-Mail

In article ,
tony sayer wrote:
Yes, Andy, it is to make a ground mat for a radio aerial... well, four
aerials actually! This requires the wires to be laid out in a fairly
precise pattern of four radial fans, and the ends soldered to bare
copper "busbars".

You should be over on uk.tech.broadcast for that sort of thing:!...

Hmm. Surely there are amateur radio groups that would be better suited?

--
*Don't sweat the petty things and don't pet the sweaty things.

Dave Plowman London SW
To e-mail, change noise into sound.

In article , Dave Plowman (News)
writes
In article ,
tony sayer wrote:
Yes, Andy, it is to make a ground mat for a radio aerial... well, four
aerials actually! This requires the wires to be laid out in a fairly
precise pattern of four radial fans, and the ends soldered to bare
copper "busbars".

You should be over on uk.tech.broadcast for that sort of thing:!...

Hmm. Surely there are amateur radio groups that would be better suited?


I don't think amateur groups do that sort of size earth mat system
Sounds like some sort of broadcast application......
--
Tony Sayer

Ian White wrote:

Thanks very much for the replies so far. I really do appreciate how you
lot get your teeth into an unusual problem!

But I misjudged the amount of detail that people might need in order to
give a helpful reply. My apologies for that - I was trying to spare you
all "the full half-hour". Well, here it comes...
snip

Try a cabling company like Nimans etc.
Although I would have thought that simply laying concrete reinforcing
mesh would have been good enough...

tony sayer wrote:
In article , Dave Plowman (News)
writes
In article ,
tony sayer wrote:
Yes, Andy, it is to make a ground mat for a radio aerial... well, four
aerials actually! This requires the wires to be laid out in a fairly
precise pattern of four radial fans, and the ends soldered to bare
copper "busbars".

You should be over on uk.tech.broadcast for that sort of thing:!...

Hmm. Surely there are amateur radio groups that would be better suited?

No - I contribute to several of those groups and lists, and can assure
you that despite it being an unusual kind of DIY problem, here *is* the
best place to ask.


I don't think amateur groups do that sort of size earth mat system

Oh yes we do - and what I'm proposing is actually a little one.

For a serious earth mat that would put many broadcasters to shame, see:
http://nidxa.org/memberWWW/k9dx_antennas.htm
There's about 40km of wire under there. I book-marked that page to
remind myself occasionally that maybe 1km isn't so hard after all...


--
Ian White

On Fri, 20 May 2005 22:41:50 +0100, Ian White wrote:

I'm looking for about 1km of thin-ish solid copper wire, as cheap as
possible.

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.

Huge wrote:
Yes, Andy, it is to make a ground mat for a radio aerial... well, four
aerials actually! This requires the wires to be laid out in a fairly
precise pattern of four radial fans, and the ends soldered to bare
copper "busbars".

Way overkill. If this is mostly over grass, cuut it very short, pin
chicken wire flat against the ground and wait. After a couple of years,
it will have vanished into the ground.


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).


--
Ian White

On Fri, 20 May 2005 22:41:50 +0100, Ian White
wrote:


1. Solid, not stranded

How about Military Surplus telephone cable, D10
(http://www.brand-rex.com/xtreme/prod...ence/Def01.pdf) 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.

--
Peter Parry.
http://www.wpp.ltd.uk/

Ian White wrote:

Yes, Andy, it is to make a ground mat for a radio aerial...

How did I guess...?

well, four aerials actually!

Ah, phased verticals (?)

1. Solid, not stranded
That is an absolute requirement - please take my word for it. (At radio
frequencies, the resistance of stranded wire becomes much higher when
the strands corrode, as they inevitably will over the years. Solid wire
is much less affected.)

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.

BTDT - enamelled is a pain to scrape and connect, especially when doing
it about 200 times, outdoors at ground level.

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.

The trick when laying wires on grass is to mow the grass very short
first. Then lay the wires along the ground, heel down any sticking-up
loops, or pin them down with thicker wire 'staples'... and then simply
leave them. Just carry on mowing a bit higher than usual (which is where
you find any loops that you didn't pin down properly) and within a year
the wires will have disappeared under the root mat. It's quite
remarkable. Within two years, you'll even have to search for half-inch
cables.

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.

If buying at normal catalogue prices, I'd rather spend all the money on
copper than on insulation that isn't needed. However, plain bare solid
copper seems to be the province of "instrument wire" suppliers, and is
sold at a huge premium compared with the copper content of say T&E.

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.

Single core is used in conduit, etc.
Stranded, alas. That is the one definite no-no for this particular
application.

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.)

Andy said:
Or get some 7-strand conduit wire (say 10 or 16 mm^2) and strip out
the strands.
Because of the total length of wire involved, I'm afraid that would be
far too labour-intensive.

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

--
Andy

Peter Parry wrote:


1. Solid, not stranded

How about Military Surplus telephone cable, D10
(http://www.brand-rex.com/xtreme/prod...ence/Def01.pdf) it
isn't stranded
(typo: isn't solid / is 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.


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

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 :-)



--
Ian White

Ian White wrote:
Thanks very much for the replies so far. I really do appreciate how
you
lot get your teeth into an unusual problem!

But I misjudged the amount of detail that people might need in order
to
give a helpful reply. My apologies for that - I was trying to spare
you
all "the full half-hour". Well, here it comes...

This is a rather unusual application, and many of the normal
electrical
wiring requirements do not apply.

I'm looking for about 1km of thin-ish solid copper wire, as cheap
as
possible.

Yes, Andy, it is to make a ground mat for a radio aerial... well,
four
aerials actually! This requires the wires to be laid out in a fairly
precise pattern of four radial fans, and the ends soldered to bare
copper "busbars".

BTDT before, but only on a smaller scale requiring much less wire.
This
time I'm doing it at a new location and on a much bigger scale.

The amount of wire required - literally more than a kilometre - means

that (a) I'll have to buy it, and (b) paying the odd few pence more
per
metre will add up to serious money.

The number of separate lengths of wires involved - approaching 200 -
means I have to think about easy "mass production" techniques. Many
of
the things you wouldn't hesitate to do for a few tens of metres are
simply not on at the kilometre scale. Wire's too long; life's too
short.


1. Solid, not stranded

That is an absolute requirement - please take my word for it. (At
radio
frequencies, the resistance of stranded wire becomes much higher when

the strands corrode, as they inevitably will over the years. Solid
wire
is much less affected.)

2. To be used as single wires, in lengths of typically 10m
3. Could be insulated or bare, tinned or not;

From the performance point of view, it makes no difference whether
the
wire is insulated or not (see, I told you this was unusual).

but not enamelled (unless
the price was very, very right)

BTDT - enamelled is a pain to scrape and connect, especially when
doing
it about 200 times, outdoors at ground level.

4. Strong enough to cope with being laid on the ground outdoors,
and
then generally trodden on and mowed over
About 1.0-1.5mm diameter would probably be fine.


Sorry, Grunff, I may have misled you by not specifying the kind of
surface. On grassy land, 1.5mm diameter copper is plenty strong
enough
for the basic radial wires - strong enough to trip someone up, and it

will even stop a rotary mower (it cuts the wire, but the wire wins in

the end, by strangulation).

The trick when laying wires on grass is to mow the grass very short
first. Then lay the wires along the ground, heel down any sticking-up

loops, or pin them down with thicker wire 'staples'... and then
simply
leave them. Just carry on mowing a bit higher than usual (which is
where
you find any loops that you didn't pin down properly) and within a
year
the wires will have disappeared under the root mat. It's quite
remarkable. Within two years, you'll even have to search for
half-inch
cables.


5. Thin enough to be cheap.

As I said, on this scale the price per metre of wire really does
matter
- especially bearing in mind it's only for a hobby. Each extra penny
per
metre becomes another 10 quid on the total cost.

Dave said:
You need to specify either cross sectional area, SWG, or what
current it
has to carry.

I'd hoped to get away without having to go into details, Dave... but
judging by some of the questions we get on here, you were quite right
to
ask :-)

For this unusual application, most of the normal electrical wiring
factors don't matter at all. It all comes down to mechanical
strength,
and price.


Single core insulated for electronic stuff is available from RS
Components
etc. Go up to normal mains - ie 1mm/sq and above and you'll get it
at any
electrical wholesaler.

If buying at normal catalogue prices, I'd rather spend all the money
on
copper than on insulation that isn't needed. However, plain bare
solid
copper seems to be the province of "instrument wire" suppliers, and
is
sold at a huge premium compared with the copper content of say T&E.

Single core is used in conduit, etc.

Stranded, alas. That is the one definite no-no for this particular
application.

Andy said:
Or get some 7-strand conduit wire (say 10 or 16 mm^2) and strip out

the strands.

Because of the total length of wire involved, I'm afraid that would
be
far too labour-intensive. The same would apply to options such as
stripping down scrap T&E. It's got to be some kind of wire that
allows
an easy "mass production" technique.

Tricky... but I really do appreciate your help and good thinking.


--
Ian White


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

Huge wrote:

Hmm. Surely there are amateur radio groups that would be better suited?


Well, there's uk.radio.amateur, but that means being in the same place as
Walt Davidson, who makes IMM look like an intellectual giant.

Walts just so much fun though ;-)))

"Ian White" wrote in message
...
....
The number of separate lengths of wires involved - approaching 200 - means
I have to think about easy "mass production" techniques. Many of the
things you wouldn't hesitate to do for a few tens of metres are simply not
on at the kilometre scale. Wire's too long; life's too short....

A wire company e.g.

http://www.knight-precision-wire.co.uk/

or 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

In message , Huge
writes
Badger writes:


Huge wrote:

Hmm. Surely there are amateur radio groups that would be better suited?


Well, there's uk.radio.amateur, but that means being in the same place as
Walt Davidson, who makes IMM look like an intellectual giant.

Walts just so much fun though ;-)))

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

More or less the same as dIMM then

--
geoff

Ian White wrote:

For a serious earth mat that would put many broadcasters to
shame, see: http://nidxa.org/memberWWW/k9dx_antennas.htm
There's about 40km of wire under there. I book-marked that page to
remind myself occasionally that maybe 1km isn't so hard after
all...

http://nidxa.org/memberWWW/k9dx_home.htm
Blimey, wouldn't it be easier to just phone them?

On Sat, 21 May 2005 12:48:54 +0100, Ian White wrote:

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.

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.

--
Cheers
Dave. pam is missing e-mail

Thats what I call an earth mat Ian!

Peter Crosland

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

Far too quick and painless.

Peter Crosland

On Sat, 21 May 2005 14:13:39 +0100, Ian White wrote:

Anyone else you know of... a bit closer to PP's GBP10/km mark, maybe?

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

Dave Liquorice wrote:
On Sat, 21 May 2005 12:48:54 +0100, Ian White wrote:

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.

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.


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 :-)


--
Ian White

Andy Wade wrote:
Ian White wrote:

Yes, Andy, it is to make a ground mat for a radio aerial...

How did I guess...?

well, four aerials actually!

Ah, phased verticals (?)

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).

1. Solid, not stranded
That is an absolute requirement - please take my word for it. (At
radio frequencies, the resistance of stranded wire becomes much
higher when the strands corrode, as they inevitably will over the
years. Solid wire is much less affected.)

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.

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.

BTDT - enamelled is a pain to scrape and connect, especially when
doing it about 200 times, outdoors at ground level.

But surely almost all 'enamelled' wire these days is solderable
polyurethane insulated and won't need scraping.

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.)



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.)

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.


Or get some 7-strand conduit wire (say 10 or 16 mm^2) and strip out
the strands.
Because of the total length of wire involved, I'm afraid that would
be far too labour-intensive.

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

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.


--
Ian White

nightjar nightjar@ wrote:

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

Yes they do - http://www.ormiston-wire.co.uk/ which I mentioned earlier
in this thread.

--
Andy

"Andy Wade" wrote in message
...
nightjar nightjar@ wrote:

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

Yes they do - http://www.ormiston-wire.co.uk/ which I mentioned earlier in
this thread.

That didn't come up when I did a search. Mind you, I stopped using them
years ago, because they were always the most expensive.

Colin Bignell

Ian

Can I ask as a electronics tech and ex radio amateur (G8HNN) who still has
a real interest in all things aerials, what freq are you using or are they
wide(ish) band ?

Dave

dave stanton wrote:

Ian

Can I ask as a electronics tech and ex radio amateur (G8HNN) who still has
a real interest in all things aerials, what freq are you using or are they
wide(ish) band ?

http://www.w8ji.com/receiving__4-square.htm

Any follow-ups about aerials as such had better be by e-mail, please.


--
Ian White

On Sat, 21 May 2005 14:13:39 +0100, Ian White
wrote:



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?

I've seen it in a number of surplus stores over the last few years -
it is usually in the 1/2mile disposable dispenser packs - a circular
olive green light canvas pack about 2ft in diameter with the wire
feeding out of the centre. The heavier refillable containers (with
straps around them) are more expensive as military vehicle
enthusiasts like them.

http://64.233.183.104/search?q=cache:YQshQyvekn4J:www.vmars.org.uk/adspage.html+d10+dispenser+pack.&hl=en&start=1&cli ent=firefox-a

had someone offering some at GBP10 a pack in March.
--
Peter Parry.
http://www.wpp.ltd.uk/

Peter Parry wrote:
On Sat, 21 May 2005 14:13:39 +0100, Ian White
wrote:



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?

I've seen it in a number of surplus stores over the last few years -
it is usually in the 1/2mile disposable dispenser packs - a circular
olive green light canvas pack about 2ft in diameter with the wire
feeding out of the centre. The heavier refillable containers (with
straps around them) are more expensive as military vehicle
enthusiasts like them.

http://64.233.183.104/search?q=cache...rs.org.uk/adsp
age.html+d10+dispenser+pack.&hl=en&start=1&client =firefox-a

had someone offering some at GBP10 a pack in March.

Thanks to both Peter and Andy for the specific references - plenty to
follow up tomorrow.

In fact, thanks again to everybody!


--
Ian White