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Re: [TowerTalk] question on copper wire used for hairpins and

To: "Jim Thomson" <jim.thom@telus.net>, <towertalk@contesting.com>
Subject: Re: [TowerTalk] question on copper wire used for hairpins and
From: "StellarCAT" <rxdesign@ssvecnet.com>
Date: Fri, 14 Oct 2016 09:00:32 -0400
List-post: <towertalk@contesting.com">mailto:towertalk@contesting.com>
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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