[TowerTalk] Wire antennas

[David Aslin]

Eric, 
Those are helpful thoughts.  I use marine pulleys (blocks) for all antenna work - they last for decades in our wet & windy UK climate.
I'm intrigued by your comment "Snatch blocks make replacing or repairing long wires quite easy."  Can you elaborate on how you use them for inverted L tails and how the repair is assisted by them?
73
David G3WGN M6O WJ6O

-----Original Message-----
From: Eric Rosenberg [mailto:ericrosenberg.dc at gmail.com] 
Sent: Tuesday, May 27, 2014 9:59 PM
To: towertalk at contesting.com; Jim Brown
Subject: Re: [TowerTalk] Wire antennas

Jim correctly said " Rope can wear and even break if it allowed to rub over a tree branch, and even in some pulleys. Absent that problem though, yes, it's the weak spots in the antenna that break."

My experience is that it certainly can. The Synthetic Textile brand is the worst offender, as its woven outer sheath doesn't last long.

My cure is two-fold. Thanks to expert advice from Eric Scace, K3NA, I use halyards with sailing blocks (aka pulleys) which are designed to work under
poor environmental conditions.   My favorite brands are Harken (US) and
Ronstan (VK), both available from West Marine and Annapolis Performance Sailing. There are many variations to chose from, so read the catalogs and spec sheets carefully. In addition, for the wires that are terminated on one end (inverted L's) I use snatch blocks made by Holt (UK) and available from both West Marine and APS. Snatch blocks make replacing or repairing long wires quite easy.

To reduce the rubbing effect of the rope going over a branch and/or having the branch grow over the rope if it hasn't been moved in a while, I use Leather Cambium Friction Savers from Sherrill Tree (who also makes the BIG Shot slingshot on steroids) . They're a bit tricky to install from the ground (especially with pine that have a lot of branches from 6 feet on up!), but well worth the effort, especially if you have climbers installing them!

Note -- these items are not inexpensive, but you *do* get what you pay for, I've never had a failure of any sort in the over 15+ years I've used them.

Finally, I disagree with Jim's cokment that by using halyards "you give up a bit of height." In my case, I can raise the antenna to the height of the cross (support) branch by raising the halyard as far as it can go -- the point where the block reaches and is stopped by the the cambium saver.

GL!

73, Eric W3DQ
Washington, DC

-----------------------------
Date: Mon, 26 May 2014 17:06:29 -0700
From: Jim Brown <jim at audiosystemsgroup.com>
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Wire antennas

On 5/26/2014 11:07 AM, K7LXC--- via TowerTalk wrote:
> The other thing you can do for wire antennas  (tnx to Jim for all his
> insights) is to use a continuous halyard. That is, the  halyard should 
> be
one
> length tied in a loop. Tie an overhand knot in it  somewhere and that 
> will give you a loop with which to hook one end of the wire  antenna.

Thank K2RD for the halyard idea. That's a good way to get a pulley up high without hiring tree climbers (expensive), but you give up a bit of height.

> I've found that in almost all cases, it's the  wire antenna that 
> breaks
> - not the halyard. Since you've got a continuous and  functioning 
> halyard, just hook the wire back to it and you're good to go. It's  
> such a PITA to replace a halyard with one end at the top of the tree 
> that this  should
save
> you some potential future misery.

Rope can wear and even break if it allowed to rub over a tree branch, and even in some pulleys. Absent that problem though, yes, it's the weak spots in the antenna that break.

And a big thank you to Steve, K7LXC, who visited me 4-5 years ago and advised me that Rohn 25 would work for me if I installed it properly and didn't put too much on it.

73, Jim K9YC