[OZAPRS] 10.147 MHz antenna

vk2tv vk2tv at exemail.com.au
Sun Dec 10 08:22:22 AEDT 2017

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.


Ray vk2tv

On 10/12/17 08:11, Glen English VK1XX wrote:
> (this info for everyone)
> 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.
> 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.
> Depending on the length.
> 3mm2, like RG213 inner is approx 132 milli ohms per meter at 10 MHz.
> so you dont need much ..
> 1mm2 about 230 milliohms per meter at 10 MHz
> glen
> On 9/12/2017 10:58 PM, Peter Dodd wrote:
>> Hi Andrew,
>> SO239 base is mounted on approx 200 x 200 mm sheet of aluminium which 
>> is bolted to the rack.
>> Rack is providing a counterpoise of sorts.
>> At this time rack does not have a good dc path to chassis (fibreglass 
>> canopy in the way).
>> In process of making earthing straps using copper strips approx 25 mm 
>> wide to remedy this.
>> Shifted antenna late yesterday and haven't redone sweep yet.
>> Should be able to get back to it tomorrow.
>> Heard by vk4mq-4 1600km so it is operational but probably not ideal
>> Regards
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> OZAPRS at aprs.net.au
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