[TowerTalk] question on copper wire used for hairpins and

[StellarCAT]

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 at 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