Hi, Gary.
According to some online skin effect calculators I found, and assuming
that the hairpin is something on the order of 4 gauge wire, the current
at 4 MHz reaches an equivalent depth of 1.4 mils or so. It is of course
a logarithmic current density profile, but the equivalent uniform
density depth is around 1.4 mils. I doubt that the tarnish is anywhere
near that thick.
73 and good to that you're still plugging away on your new station,
Dave AB7E
On 10/13/2016 2:05 PM, StellarCAT wrote:
So ... Force12 used (uses!) bare copper wire as their hairpins. I have a 80/75 rotary dipole that has a hairpin made from
bare #10 wire ... it is now 11 years old and it looks dull – tarnished ... not corroded at all – just the
dull brown color that copper gets to be ... is there any reason why that can’t be reused (I’m putting it
back up)? I realize the skin effect will mean that only the outside such-n-such micrometers are used for conductance ...
but would any resistance in the ‘tarnish’ factor in or would it appear to be the same today as it was when
brand new?
My guess is the answer is yes – it can be reused and it would continue to work as if it were brand new ...
and my one point of argument towards that fact is that when it was up – for 7 years – there was no
apparent change in the operation of the antenna! The SWR didn’t change, which is what the hairpin would
most drastically effect ... the 2:1 bandwidth didn’t change noticeably (Q) ...
thoughts and discussions...
Gary
K9RX
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