[TowerTalk] question on copper wire used for hairpins and the like...

[StellarCAT]

Thanks Dave ... its 8 ga.

getting nervous with all the stuff yet to do. Here's something you'll 
connect with: I have to fabricate my own bracket to mount the Optibeam 
OB40-4 to the tower as with their system the center of mass is right on the 
HUGE bolts that hold the boom sections together. So I have to space the 
mounting plate away from the boom by 1/2". Using 1/2" x 3/4" aluminum bar 
stock to do this.

Gary

-----Original Message----- 
From: David Gilbert
Sent: Thursday, October 13, 2016 9:22 PM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] question on copper wire used for hairpins and the 
like...



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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