On Fri, 06 Oct 2006 05:21:00 GMT, Tony VE6MVP
wrote:

Folks

So I'm reading the 2006 ARRL Handbook page 22.6, There is a single
line stating "Steel wire is a poor conductor at RF; Avoid it." Any
idea why? Or is this just one of those physical properties?

So how much poorer than copper? Steel clothesline is easily obtained
and not that expensive. Admittedly though I haven't done much
research on copper or the other type of wires the Handbook mentions.


I am guessing that the "steel clothesline" to which you refer is
probably actually stranded (7x1?) heavy galvanised soft steel wire.

The galvanising is zinc or zinc/aluminium alloy and its thickness has
bearing on the answer for a specific frequency.

The stranding also has adverse effect on the effective RF resistance,
though not as predictable as the zinc coating.

Though it works, there are a number of mechanisms that increase the
loss, and the extent of some of them are quite difficult to predict or
to measure (for the average amateur).

The additional loss of steel wire is less important in an antenna
design that is loaded with bulk resistance, eg T2FD. A reason why
small guage stainless steel wire commonly used commercially on these
antennas isn't necessarily unsound. But that application should not
imply that small guage stainless steel is just as suited to a half
wave folded dipole.

Antenna wire would be one of the lowest cost elements of a complete
system, which questions the cost effectiveness of savings.

Owen
--