[TowerTalk] [Bulk] Re: The other end of Phillystran - connections to the tower

[Grant Saviers]

I'm curious what a "bent pin shackle" looks like.  I know there are bow, 
D, chain, and sling shackles all with various types of straight pins, 
e.g. threaded, pin, bolt.

Crosby is the top US maker, Chicago is another US brand at a cost 
savings.  Check rigging supply house near you for inventory or McMaster 
or uscargocontrol.com

Thanks for the tip re 10m interaction with big grips, I think I have 
that problem.

Grant KZ1W

On 3/19/2016 2:58 AM, George Dubovsky wrote:
> But where do you get those shackles today? I have used Joslyn shackles in
> the past, acquired from another ham, but when I went looking for more two
> years ago, I couldn't find a vendor. I know it's utility hardware, but I
> couldn't figure out how to buy any.
>
> 73,
>
> geo - n4ua
>
> On Sat, Mar 19, 2016 at 3:32 AM, Tim Duffy <k3lr at k3lr.com> wrote:
>
>> When installing the tower connection end of Phillystran guy cables, I
>> learned that a significant problem can happen with unintended Yagi guy grip
>> (Preform) antenna interaction.
>>
>>
>>
>> The problem is this, if your guy grip tower terminations are close to your
>> antenna mounting position (right underneath), and the terminations (guy
>> grips) are electrically connected to the tower, they can (in many
>> installations) interact and cause antenna pattern/VSWR problems. This
>> problem is worse on the higher bands like10 and 15 meters.
>>
>>
>>
>> For example at K3LR many Yagi's are side mounted on ring rotors.
>> Phillystran
>> or fiberglass guy attach to the tower right under each ring rotor. After an
>> installation several years ago of some 10 meter Yagi's I noticed that there
>> were three peaks and valleys in VSWR when rotating the antenna mounted on
>> the ring. Closer inspection and modeling the three short lengths of
>> "connected" guy grips revealed that in fact the Preform guy grips were long
>> enough (cumulative effect of 3 together) to impact the near field
>> environment of the Yagi. The problem is worse the more "horizontal" the guy
>> wire is relative to the Yagi (lower guy wire connection points heading to
>> ground mounted concrete guy dead men anchors) and the higher in frequency
>> the antenna is (Preform length is more "meaningful").
>>
>>
>>
>> The solution is simple enough and easy at the time of installation. All of
>> my guy grip installations now include a "bent pin shackle" (tower side) and
>> a properly sized guy wire insulator - right at the guy attachment point on
>> the tower. The other side of the insulator contains the proper guy grip for
>> the Phillystran or Fiberglass guy material. This way the Preform is totally
>> insulated from the tower.
>>
>>
>>
>> Once the insulators were installed at the tower connections, the VSWR and
>> directional pattern of the Yagi antenna remained constant and predictable
>> (as modeled) no matter where the antenna was pointed.
>>
>>
>>
>> You can see the tower insulators installed on the K3LR 20 meter tower on
>> this W8WWV drone video at the 5:18 mark
>>
>>
>>
>> https://www.youtube.com/watch?v=SA_NG-bVQuc
>>
>>
>>
>>
>>
>> 73
>>
>> Tim K3LR
>>
>>
>>
>>
>>
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>>
>>
>>
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