[Lowfer] Al Loop Conductor?

K2ORS k2ors at verizon.net
Mon Nov 7 22:03:59 EST 2011 

Using Scott's 4:1 ratio for weight of copper:aluminum, a quick calculation 
shows that aluminum has about a 40% lower Rac at 185.3 kHz.  I believe that 
a 4:1 ratio was also quoted for the relative costs of copper to aluminum.
So for equal $ that means Al is 40% better than copper (at 185.3).

Warren

----- Original Message ----- 
From: "K2ORS" <k2ors at verizon.net>
To: "Discussion of the Lowfer (US, European, &amp; UK) and MedFer bands" 
<lowfer at mailman.qth.net>
Sent: Monday, November 07, 2011 9:06 PM
Subject: Re: [Lowfer] Al Loop Conductor?


> Bill,
>      There is a nice online calculator that allows you to calculate Rac 
> for
> any frequency if you put in the material properties (resistivity and
> permeability, for Copper and Aluminum permeability is 1.0)
> http://www.mantaro.com/resources/impedance_calculator.htm
>
> (Scroll down the page about 1/2 way).
>
> Cheers,
>
> Warren
>
>
>
> ----- Original Message ----- 
> From: "Bill Ashlock" <ashlockw at hotmail.com>
> To: <lowfer at mailman.qth.net>
> Sent: Monday, November 07, 2011 8:31 PM
> Subject: Re: [Lowfer] Al Loop Conductor?
>
>
>>
>> Interesting detail, Warren! Things are looking even better for Aluminum
>> (Now if we could only solder to the darn stuff with simple equipment :).
>> That WAS 100Khz, so we need data for higher frequencies, before we can
>> fall in love with it. I'll see what I can find. Now I'm wondering what it
>> is about an element that defines its skin depth. (??)
>>
>> Bill
>>
>>> From: k2ors at verizon.net
>>> To: lowfer at mailman.qth.net
>>> Date: Mon, 7 Nov 2011 20:04:37 -0500
>>> Subject: Re: [Lowfer] Al Loop Conductor?
>>>
>>> Bill,
>>>       I received the following comment from Rik Strobbe:
>>> "Hi Warren,
>>>
>>> aluminium has a higher resistivity (28x10^-9 Ohmmeter) than copper
>>> (17x10^-9
>>> Ohmmeter) but it has a larger skin depth (Al = 260 um, Cu = 210 um at
>>> 100kHz).
>>> That makes an Al wire only 33% worse than a Cu wire of the same 
>>> diameter.
>>> Regarding mechanical strength it might be a good idea to inforce this by
>>> a
>>> steel wire support.
>>>
>>> 73, Rik  ON7YD - OR7T"
>>>
>>> ----- Original Message ----- 
>>> From: "Bill Ashlock" <ashlockw at hotmail.com>
>>> To: <lowfer at mailman.qth.net>
>>> Sent: Monday, November 07, 2011 7:58 PM
>>> Subject: Re: [Lowfer] Al Loop Conductor?
>>>
>>>
>>> >
>>> > Hi again Scott,
>>> >
>>> > Thank you for the positive comments on my loop experiments. I am
>>> > looking
>>> > forward to doing a similar study of loop performance variables at 
>>> > 500K,
>>> > particularly with loops supported and in full contact with trees.
>>> >
>>> > I got to thinking about your use of #2 ga Aluminum and checked out my
>>> > Loop
>>> > Article #2 which has a comparison of various conductors types (185K). 
>>> > I
>>> > show the Rac of #2 copper to be close to that of RG-8 and was 
>>> > wondering
>>> > if
>>> > you or anyone else has had the chance to compare these Racs. I would
>>> > think
>>> > that just the difference in Cu vs Al would amount to a 1.7X increase 
>>> > in
>>> > Rac for the #2 Aluminum...But considering you are running an 
>>> > incredible
>>> > 50
>>> > Amps I realize this is a totally different ball game. Maybe it should
>>> > be
>>> > called "The Battle of the Loop Conductor Meltdowns" :)
>>> >
>>> > Best regards,
>>> >
>>> > Bill
>>> >
>>> >> Date: Sun, 6 Nov 2011 18:05:49 -0800
>>> >> From: sthed475 at telus.net
>>> >> To: lowfer at mailman.qth.net
>>> >> Subject: Re: [Lowfer] Al Loop Conductor?
>>> >>
>>> >> 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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