[Lowfer] Al Loop Conductor?

Bill Ashlock ashlockw at hotmail.com
Tue Nov 8 19:03:53 EST 2011 

Thanks for the good info in those tables and excellent comparisons you have made, Warren.

Next thought provoker: What about using Aluminum in loading coils? Especially ones that hang from the antenna's top hat.

Bill

> From: k2ors at verizon.net
> To: lowfer at mailman.qth.net
> Date: Mon, 7 Nov 2011 22:03:59 -0500
> Subject: Re: [Lowfer] Al Loop Conductor?
> 
> 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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