Is there an optimum angle for antenna mast guy wires? I will be using three
guy wires and am a bit limited in real estate.

Just curious.


VK5JE


-----------------------------------------
You have hobbies. I have hobbies.
Chances are I have one that you don't.
I'll leave it up to you to decide!
http://www.flightsimulatorandhobbies.com/
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"JERD" wrote in
:

Is there an optimum angle for antenna mast guy wires? I will be using
three guy wires and am a bit limited in real estate.

As you increase the elevation of guy wires, under lateral forces on the
structure from wind, you:
- increase the tension in the guy wires;
- increase the downwards (buckling) force on the mast;
- increase the upwards (pull out) force on the guy anchors.

Owen

From my studies in geometry, trig and physics, I believe the optimum angle
is 45 degrees. Put the anchors as far out as you can, and attach the guy
wire to the antenna mast wherever a 45 degree angle puts it, whether that is
at the top, in the middle or lower down. Just understand that the part of
the mast above where the guy wire connects will be subject to bending forces
from wind. And the further it extends above the guy wires the greater those
bending forces will be at the point where the guy wires connect.

My $.02

Dave

"JERD" wrote in message
...
Is there an optimum angle for antenna mast guy wires? I will be using
three guy wires and am a bit limited in real estate.

Just curious.


VK5JE


-----------------------------------------
You have hobbies. I have hobbies.
Chances are I have one that you don't.
I'll leave it up to you to decide!
http://www.flightsimulatorandhobbies.com/
-----------------------------------------

"Dave" wrote in
:

....
connects will be subject to bending forces from wind. And the further
it extends above the guy wires the greater those bending forces will
be at the point where the guy wires connect.

.... and the bending moment assists buckling of the section of mast below
the top guys... then ...

Owen

JERD, VK5JE wrote:
"Is there an optimum angle for antenna mast guy wires?"
Many factors are involved in guying a mast. Read the "ARRL Antenna
Book" chapter on "Antenna Supports" or some similar authoritative
information aimed at your level of civil engineering expertise.

Best regards, Richard Harrison, KB5WZI

On Dec 4, 10:54 am, (Richard Harrison)
wrote:
JERD, VK5JE wrote:

"Is there an optimum angle for antenna mast guy wires?"
Many factors are involved in guying a mast. Read the "ARRL Antenna
Book" chapter on "Antenna Supports" or some similar authoritative
information aimed at your level of civil engineering expertise.

Best regards, Richard Harrison, KB5WZI

Exactly as Richard replied. Other considerations are the type of
antenna. For any type of dipole or similar antenna one guy or set of
guys must be directly in line with the wire of the antenna. Otherwise
the pull of the antenna will surely bring down you mast. Then spread
the other two guy wires 120 degrees from the back guy.

What type of mast are you putting up and how high?

For example, this summer I began putting up a 160 meter lazy quad
using four 4 section push-up steel masts. Each section is 10 ft. with
a 1 ft overlap giving a full height of about 36 feet. A mast is at
each corner of the rectangle. I couldn't quite get a square. I have 3
screw-in ground anchors set at 30 ft from the mast. All guys are
attached to one anchor. The first set of guys is attached at the 10 ft
mast ring so the mast set can be anchored vertically before raising
any of the nested pieces.

A second set of 3 guy wires is attached at the third section ring and
a single guy wire is attached to the very top of the top section. The
second guy ring is left empty. Using a step ladder, I can pull up and
lock section after section till all are extended. Then the second and
the top guy wires are attached to the ground anchor and all are
snugged up until the whole mast is vertical.

One ground anchor is set behind the mast so its guy wires and the mast
are in line with the mast on the opposite corner of the rectangle. The
other two anchors are set at 120 degrees from the back anchor.

Each mast has a pulley and rope to pull the insulator and antenna wire
up into the air. When all is raised, the antenna wire and the back guy
on each mast give the equivalent of three guy wires at the top of each
mast. This was all theory until last weekend. We had a HELL of a wind
storm. Blew fences down, metal roofing off other guy's shop, etc. The
quad antenna hardly moved!

I still have to finish the 600 ohm feed line. I was tempted to use 450
ohm window line, but after the wind storm, I know it would have been
whipped to pieces. So, I don't know how well the antenna will actually
work, yet, but there is hope.

Perhaps this discourse will give you some other ideas on guying your
mast.

73's
Paul, KD7HB