[TowerTalk] Long Wire Sag

[Bob Shohet, KQ2M]

Hi Gedas,

I’m glad that you have not yet had a break.  That is more common when there is little or no tension placed on the wire or the antennas have not been up long enough.  :-)    The problem comes when anything abrades the pvc coating and then moisture/rain seeps through the coating and begins to oxidize/pit the strands of wire.  This is inevitable as the coating begins to break down eventually under sunlight, tension and wx, and much more quickly when under tension and/or abrasion.  THHN solid is a bit more resistant to this process as the thickness of the one “strand” is much greater and it will take more wear to corrode/pit it significantly than a much thinner single strand out of a bundle of strands.

I have actually found it more difficult to solder the stranded wire as opposed to the solid.  But that maybe because I always use a utility knife to gently scrape the wire where I am going to solder.  That leaves the bare copper which  takes the solder very quickly and makes an excellent connection both electrically and mechanically.

I have also heard that solid is more likely to stretch than stranded but I have not seen the resonant freq. of my antennas change over time so if there is stretching occurring then it is not significant for my purposes.  That might be different if the antennas are under significant tension for a long period of time but I have not seen anyone document this as an important issue for ham antenna purposes.   

73

Bob, KQ2M


From: Gedas 
Sent: Sunday, March 10, 2019 12:34 PM
Cc: towertalk at contesting.com 
Subject: Re: [TowerTalk] Long Wire Sag

Hi Bob. Thank you very much for sharing your experiences. I have always 
used #14 stranded here for 40m and 80m antennas and knock on wood have 
not had a wire break....I found the stranded was a lot easier to work 
with and esp to solder to. I also thought the stranded would stretch 
less then the solid but it may in fact be the other way around.

I see Jim has replied and I want to read what he has said and hope I can 
put what he has said to use. I have been getting a lot of nice tips from 
people via PM and need to start digesting it all. Thank you again !


Gedas, W8BYA

Gallery at http://w8bya.com
Light travels faster than sound....
This is why some people appear bright until you hear them speak.

On 3/10/2019 11:55 AM, Bob Shohet, KQ2M wrote:
> Hi Gedas,
> I use #10 for 160,  #12 for 80 and #14 for 40.
> The #10 NEVER breaks – not even in frequent ice storms  – only the 
> wire connectors that I use with them.  #12 for 80 almost never breaks 
> and #14 breaks after enough wear and tear in 1 – 3 years especially in 
> a high wind environment where flexing of the outer coating is 
> commonplace and where significant tension is involved.
> I believe that #12 THHN SOLID (not stranded) is the best compromise of 
> weight, strength and cost.  #14 will break given enough time and the 
> few bucks that you save with it over #14 is not worth it.  In my 
> experience the difference in weight should not be significant unless 
> you are supporting a lot of ice.  I know that the Wireman sells a #13 
> pvc coated poly – and I used to use that but found that its life 
> expectancy was significantly less than the #12 THHN and #14 THHN that 
> I could buy for a fraction of the cost at Home Depot or Lowe’s in a 
> 500’ spool.
> I strongly recommend SOLID and not stranded because in my experience 
> the stranded THHN breaks more frequently than the solid.
> The #14, weighing less than #12, will have less sag, but is not as 
> strong, will flap around more in the wind it is not as strong and is 
> far more likely to break under tension, especially when supporting ice 
> or wet snow.
> 73
> Bob KQ2M
> *From:* Gedas <mailto:w8bya at mchsi.com>
> *Sent:* Sunday, March 10, 2019 11:25 AM
> *Cc:* towertalk at contesting.com <mailto:towertalk at contesting.com>
> *Subject:* [TowerTalk] Long Wire Sag
> I am planning to put up a long inverted v antenna with it's feedpoint at
> 85' using 600' total wire (300' on each leg). The ends will be near the
> ground, only 20-25 feet high.
>
> My question is given that each leg of this antenna will be 300' long am
> I better off going with a lighter weight #14 THHN insulated stranded
> wire or some heavier #12 THHN stranded? I am not going to purchase a
> different wire that would be better suited like copper-weld etc since I
> have plenty of these other two and want to try something today.
>
> I realize there is going to be a _lot_ of sag in either case but I am
> not sure of the breaking strengths of either #12 or #14 and in the end
> which will help keep the wire up higher with less sag. Any ideas?
>
> Gedas, W8BYA