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@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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