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@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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