[Lowfer] Al Loop Conductor?

Bill Ashlock ashlockw at hotmail.com
Mon Nov 7 20:31:10 EST 2011 

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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