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@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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73
Roger (K8RI)
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