[TowerTalk] Wire antenna in trees? (Patrick Greenlee) (Kelly Taylor)

[Grant Saviers]

re #3

I use a pull down line of parachute cord tied to the hoist line on the 
pull side of the insulator so when something breaks - wire, coax, or 
insulators I can retrieve the hoist line top end.  Or, make the hoist 
line a loop with a short tail for the insulator, but that takes a bit 
more of the larger, more expensive line and can be confusing to the 
ground crew.

The CMI  pulleys are great, I use them for rigging stuff.  For wire 
antennas, I use marine ball bearing blocks (single sheave pulleys) which 
substantially reduce the friction and line wear (smooth, never jam, last 
forever, and the line runs straight with their swivels). About $15, if 
you shop around on the web for Lewmar, Harken, or Ronstan.   More 
expensive at West Marine, in my experience.

Grant KZ1W

On 8/6/2017 13:23 PM, Jim Brown wrote:
> I use water jugs (don't remember capacity, only weight) filled with 
> dry sand. They weigh 95 -100#, which is my estimate of the tension on 
> a centerfed horizontal wire.  I use CMI rescue pulleys and mostly 
> 5/16-in Synthetic Textiles rope. On the longest run that's under the 
> greatest tension, I use 7/16-in rope. Both ends have pulleys. On each 
> antenna, one end is tied down, the other end has the weight.
>
> In my 11 year experience with antennas in these tall trees, the 
> failure modes are
>
> 1) Wire connection/tie-off points (solder is bad, loops through eyes 
> that double back on the wire and split bolt connectors to secure both 
> electrical and mechanical connections are good. A good rule is to 
> never solder a connection that will be stressed -- eventually the 
> stressed wire will break at the soldered connection.
>
> 2) Wear on the support rope where it goes through a pulley. That's why 
> I use 7/16-in for the longest, highest antenna.
>
> 3) Poorly made center insulators.  Even with the best, I've learned to 
> add rope across the insulator so that the dipole doesn't hit the 
> ground if the insulator fails. (Getting two ends of a dipole up that 
> high costs at least $800 for a day's worth of a guy in the trees and a 
> helper on the ground. The last thing I want is for them to come back 
> for something in the antenna that broke, releasing one or both support 
> ropes so that the pulley must be re-strung.  Ask me how I know. :)
>
> 73, Jim K9YC
>
>  On 8/6/2017 12:44 PM, Clay Autery wrote:
>> Roger that, Jim.  Until I can get my ENTIRE loop path clear of
>> vegetation, I will have to accept the trade-off and continue to use the
>> insulated stuff.  (Maybe this winter, fingers crossed).  Since I can
>> pull the entire loop down in about 10 minutes, keeping it pruned to
>> tuned length isn't much of a task...  Mine aren't nearly as high up as
>> yours.  :)
>>
>> I'd love to give the bare solid stuff a try...  How much weight do you
>> have to use to keep it tensioned in the air?  280+ feet of #8 would be
>> some bit heavier...
>> And I'd definitely have to come up with a bigger diameter pulley.  :)
>>
>> ______________________
>> Clay Autery, KY5G
>> MONTAC Enterprises
>> (318) 518-1389
>>
>> On 8/6/2017 1:40 PM, Jim Brown wrote:
>>> The problem with using ordinary copper wire for antennas where the
>>> wire is under tension is that it stretches. Mine high dipoles are
>>> under about 100# of tension (up 140 ft, fed with RG11), so every few
>>> years, I have to let down my 80/40 dipole that's built with #10 THHN
>>> stranded and circumcise it to keep it on frequency. I've since
>>> migrated to using #8 bare solid copper that I've stretched by tying
>>> one end to a tree and the other end to the trailer mount of my SUV and
>>> pulling slowly until it breaks.  The result is close to being hard
>>> drawn, roughly AWG #9, and about 15% longer. Antennas that I've built
>>> with this seem not to stretch.  Over the years, W6GJB and I have done
>>> this with at least 2,000 ft of #8.
>>>
>>> 73, Jim K9YC
>>>
>>> On 8/6/2017 10:44 AM, Clay Autery wrote:
>>>> Correct...  THHN is not intended for use as exterior antenna wire, but
>>>> it surely does work well...  I can get it in any color I want and in a
>>>> 2500+ foot spool, et al.
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>