[Lowfer] Al Loop Conductor?

[Scott Tilley]

Greetings Bill

I have only built one single conductor (#2AWG AL) loop thus far and it 
works very well and have no data to offer comment on Rac of CU vs AL...  
Thanks to your efforts much of my design effort was based on your very 
good papers on the topic and designing a tuner that could handle in 
excess of 50A key down.

Using indirect means of approximately determining the impedance of my 
loop revealed a better than expected performance when compared to 
modeled solid circular conductor.  I'm making an educated guess 
(hypothesis) that this is related to the greater surface area of the 
stranded conductor itself.  Perhaps this is something you care to study 
in greater detail?

My qualitative opinion of this being the 'perfect' loop conductor was 
based on my wallet not being greatly lightened to purchase the conductor 
and my back not overly strained to carry it away and install.  I believe 
this is an engineering compromise that I feel favours the sensibilities 
of most operators (price and weight vs a slight compromise on the 
performance CU would provide.)  As I have alittle more leeway on 2200m 
compared to the Lowfer band this compromise MAY amount to something 
negligible and be overwhelmed by the other advantages.  Maybe not so on 
Lowfer?

During operation, it appeared to perform well enough that for me there 
was no interest in delving into the nuisances as JA7NI awaited... 
Particularly since I could achieve my 1W EIRP with ease now.

Is my overall hypothesis correct? I'll leave that to the experts such as 
yourself to explore and explain.

73 Scott



On 11/6/2011 5:06 PM, Bill Ashlock wrote:
> Hi Scott,
>
> Considering the exchange of info on this topic I conclude we have the density and DC resistivity of Cu vs Al pretty well in hand but what about the Rac of Cu vs Al? Has anyone measured the Rac of aluminum conductors... and at different frequencies? Also we shouldn't forget the 'proximity effect' and the 'skin effect' when using large diameter conductors. I proved at 185K that the reduction in Rac was quite small when the conductor diameter was increased. Even separate insulated conductors twisted together netted little improvement over a single conductor and only when the spacing was approximately 1" was there a worth-wide improvement. Twisted, insulated, conductors do not define Litz cable. The interweaving needed is much more complex than this.
>
> Bill
>
>> Date: Fri, 4 Nov 2011 21:07:43 -0700
>> From: sthed475 at telus.net
>> To: lowfer at mailman.qth.net
>> Subject: Re: [Lowfer] Al Loop Conductor?
>>
>> Hi Warren
>>
>> My 100m perimeter LF loop is constructed of similar AL wire.  You'll
>> find it the PERFECT loop conductor as it's much lighter and cheaper than
>> copper.  The conductivity issue is not that big of a deal as my
>> conductor had much better conductivity than calculated.  I figure this
>> is due to the increased surface area based on the stranded nature of its
>> construction.
>>
>> Another nice feature of neutral supported cable type conductor is the
>> insulation is tough and will have been tested by UL/CSA or similar to
>> have a dielectric withstand in excess of 3KV.  No arcing here ever.
>>
>> Just ensure you use a suitable compound on any joints to mitigate oxidation.
>>
>> 73 Scott
>> VE7TIL
>>
>>
>> On 11/4/2011 5:29 PM, K2ORS wrote:
>>> Hi,
>>>       I am considering using Aluminum service drop wire (3/0 gauge) as a
>>> conductor for an LF transmitting loop. I know that the conductivity is not
>>> as good as copper but it weighs so much less that I can use a larger
>>> diameter conductor.
>>> Has anyone tried this? How would it hold up when flexed by the wind ? Other
>>> thoughts?
>>>
>>> 73 K2ORS
>>>
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