that's what I was thinking - that the tarnish would be more like insulation
and the current would simply flow through the copper below (low resistance
path) ...
g.
-----Original Message-----
From: Jim Thomson
Sent: Friday, October 14, 2016 8:15 AM
To: towertalk@contesting.com
Subject: [TowerTalk] question on copper wire used for hairpins and
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
### Dull and tarnished has zero effect. Its the connections on each end
that you have to worry about. The rf current simply travels beneath the
tarnish. As long as the connections on each end are good, you are good to
go. In most cases, F12
terminated the helical hairpin coils with crimped and soldered lugs...so
the end terminations are not an issue. There is one heckuva lot of
current in the hairpin though. Id use something bigger, like 8 ga bare cu
or 8 ga magnet wire, or .187 or .250
cu tubing, with the ends flattened.... then punch /drill .187 holes to
handle the 10-32 / 10-24 SS machine screws they used.
Jim VE7RF
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