[Lowfer] Al Loop Conductor?

Mon Nov 7 19:58:24 EST 2011

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
> >>>
> >>> ______________________________________________________________
> >>> Lowfer mailing list
> >>> Home: http://mailman.qth.net/mailman/listinfo/lowfer
> >>> Help: http://mailman.qth.net/mmfaq.htm
> >>> Post: mailto:Lowfer at mailman.qth.net
> >>>
> >>> This list hosted by: http://www.qsl.net
> >>> Please help support this email list: http://www.qsl.net/donate.html
> >>>
> >> ______________________________________________________________
> >> Lowfer mailing list
> >> Home: http://mailman.qth.net/mailman/listinfo/lowfer
> >> Help: http://mailman.qth.net/mmfaq.htm
> >> Post: mailto:Lowfer at mailman.qth.net
> >>
> >> This list hosted by: http://www.qsl.net
> >> Please help support this email list: http://www.qsl.net/donate.html
> >   		 	   		
> > ______________________________________________________________
> > Lowfer mailing list
> > Home: http://mailman.qth.net/mailman/listinfo/lowfer
> > Help: http://mailman.qth.net/mmfaq.htm
> > Post: mailto:Lowfer at mailman.qth.net
> >
> > This list hosted by: http://www.qsl.net
> > Please help support this email list: http://www.qsl.net/donate.html
> >
> 
> ______________________________________________________________
> Lowfer mailing list
> Home: http://mailman.qth.net/mailman/listinfo/lowfer
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Lowfer at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html