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

[George Dubovsky]

Google Joslyn J372. Another fellow told me that they are available from
Hubbell Power Systems, but 50 is the minimum order. Some enterprising DX
type ham, perhaps with an ENGINEERING connection, might consider selling
them... ;-)

73,

geo - n4ua

On Sat, Mar 19, 2016 at 12:29 PM, Grant Saviers <grants2 at pacbell.net> wrote:

> 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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>>
>>
>>
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>