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

Sat Mar 19 12:47:18 EDT 2016

I just used the 45G guy brackets. There is a through bolt at each 
corner. I just put the saddle in the "Big Grips".  The guys were about 
10' below the tribander.

I'd be more concerned about RF noise with a direct connection to the 
tower, particularly on VHF. When I had steel guys, I could rub a 10" 
screwdriver against the guy and create a tremendous hash. This was just 
above the insulator isolating the guy from the anchor
The guy connection to the tower  was about 10' below the 2-meter antenna.

I've had no problems on 40 through six.

73

Roger  (K8RI)

On 3/19/2016 Saturday 12:29 PM, Grant Saviers 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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-- 

73

Roger (K8RI)

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