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<p><font face="Arial">Glen touches on something that is not widely
known. Aluminium and Stainless Steel are much further apart on
the galvanic table than aluminium and Zinc, and the former
combination will corrode much more quickly than the latter. One
assumes the use of "proper" (hot dipped) galvanising and not
that rubbish sold at large hardware chains where a zinc rod is
waived somewhere near the base metal.</font></p>
<p><font face="Arial"><a class="moz-txt-link-freetext" href="https://corrosion-doctors.org/Definitions/galvanic-series.htm">https://corrosion-doctors.org/Definitions/galvanic-series.htm</a><br>
</font></p>
<p><font face="Arial">Ray vk2tv</font><br>
</p>
<br>
<div class="moz-cite-prefix">On 10/12/17 08:11, Glen English VK1XX
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:e686da84-49ff-649c-e7be-5dcaa4df0678@pacificmedia.com.au">(this
info for everyone)
<br>
<br>
Peter, on your copper straps- be sure to use a zinc based jointing
compound between the copper and aluminium... or a large Zinc(Gal)
washer. ...and avoid stainless in there. The Gal washer works
well.
<br>
<br>
On a more practical note, on the copper straps, given that the
the ground you are trying to connect to is 10 to 20 ohms, an ohm
of RF resistance wont hurt ! wide copper is not necessary... so
something like a couple of 4mm2 wires soldered to crimp lugs (as
the Cu-Zn-Al interface) will do the job.
<br>
Depending on the length.
<br>
<br>
3mm2, like RG213 inner is approx 132 milli ohms per meter at 10
MHz.
<br>
so you dont need much ..
<br>
<br>
1mm2 about 230 milliohms per meter at 10 MHz
<br>
<br>
<br>
glen
<br>
<br>
On 9/12/2017 10:58 PM, Peter Dodd wrote:
<br>
<blockquote type="cite">Hi Andrew,
<br>
SO239 base is mounted on approx 200 x 200 mm sheet of aluminium
which is bolted to the rack.
<br>
Rack is providing a counterpoise of sorts.
<br>
At this time rack does not have a good dc path to chassis
(fibreglass canopy in the way).
<br>
In process of making earthing straps using copper strips approx
25 mm wide to remedy this.
<br>
Shifted antenna late yesterday and haven't redone sweep yet.
<br>
Should be able to get back to it tomorrow.
<br>
Heard by vk4mq-4 1600km so it is operational but probably not
ideal
<br>
Regards
<br>
<br>
</blockquote>
<br>
<br>
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</blockquote>
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