many thanks to those who replied to my email regarding telephone drop wire.
The material I have is not copper coated steel wire - it looks like
copper material all through.
The conductors are 1mm diameter and the black insulation is about 1.25mm
thick. The pair of wires are 2.5mm apart. I have used it as twin feeder
to an OCFD for the HF band to good effect.
G3JMG, in an article in RadCom March 1970 noted that BT had their own
recipe for the conductors of drop wire: an addition of one per cent
cadmium to the basic copper mix. This increased the tensile strength of
hard drawn copper by 50% from 30 tons psi to 30 tons psi. This also
increased the DC resistance by about 20%.
regards
Peter, G3LDO
On 16 May 2008 at 7:08, Laurence KL1X wrote:
..........I never had to deal
with open wire spans by the time of my apprecticeship but I think
that was very similar physically.
There was some open wire around when I was a BT (Post Office)
apprentice. It was solid copper wire. As I recall, dropwire (steel
with a thin copper coating) had a limit to its usable length because
it had a higher DC resistance than open wire. This resistance may not
be high in relation to other losses on an LF Marconi, but it would
rule out its use in a transmitting loop antenna.
Mike, G3XDV
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