[Harc] ROOF MOUNT

[Mark Nelson]

This fellow seems to know of what he speaks!  sages
1aRe: Metal Roofs and Hex-Beams
<https://groups.yahoo.com/neo/groups/hex-beam/conversations/topics/18505;_ylc=X3oDMTJyYWg2bzdrBF9TAzk3MzU5NzE1BGdycElkAzQ0NTUxNTMEZ3Jwc3BJZAMxNzA1MDYzMTA4BG1zZ0lkAzE4NTA1BHNlYwNkbXNnBHNsawN2bXNnBHN0aW1lAzE1NTk0NDUyMDI->
Sat Jun 1, 2019 6:06 pm (PDT) . Posted by:wise2437
<rfg8yg at xalaska.com?subject=Re%3A%20Metal%20Roofs%20and%20Hex-Beams>
I was in the commercial radio business for years. I found out that any type
of mast that lays along a building and sticks up past the roof is a waste
of time and money. Here is what works.



Put a hinge in the center of the roof. Barndoor hinges are fine.
Bolt or weld a pipe flange to one leg of the hinge.
Put a 21 ft 2" or 1.5" galvanized water pipe.
Put a guy wire ring about 70% or 80% of the way up. Muffler clamp to
prevent sliding down.

Use 4 guy wires.
Lay the pipe down over the edge of the roof. On peaked roofs, I use the
eave.
Set two guys along the roof peak.
Stand antenna up and set and adjust the two guys going to the eave.
You could calculate or guess these last two wires.
The antenna stands up easily, pulling against one of the eave wires.
Fasten the other eave wire.
Voila, 21 ft above the roof.
You can extend the 2" pipe with smaller pipe. 1.5" is a good fit.
I suggest you weld any extensions, as threaded fittings can crack.
If you go taller than the 21', or with big antennas, you may need two set
of guys.
Make sure the guys are not 1/2 1/3 or 1/4 of the distance from the ends. It
sets up

mechanical resonances. I once had one of these pipes guyed at the middle
and it danced
like a hula belly dancer. Moved the ring up a few feet, presto!
Guy wires should NOT be humming tight. It is ok if the pipe top sways a
foot or so.
As the guy comes up against the wind, motion is dampened. Lot less stress
that way.
I have one here downtown Nome, not in use but still standing, Since 1982.
By the way ... I suggest no less than 3/16 guy wire. The smaller one will
break
due to electrolysis or galvanic corrosion. I looped my wires thru thimbles,
and the
break was at the peak of the thimble. That was with 1/8 wire. Inspection
showed
like burning of the wire at this point.
Roof guy anchors should be BOLTED not lagged. Pipe hinge can be lagged as
the forces are perfectly downwards.
I prefer forged eye bolts for guys. The ones that are just bent into a loop
have a
tendency to open up unless they are Bejesus strong. Like 3/8 minimum. The
pull
of wires is relentless. You can also weld the gap closed on open ones. But
welds
here like to corrode.

Always bring all feedlines to the hinge, then away. Never, ever from
mid-pipe.
It helps to have a barrel coax connector at the hing area in case something
has
to be troubleshot or replaced. For professional work, the feedline can
often be
inside the mast, and then in conduit from the hinge to the radio.



There is an cell tower here. Rohn 55G. Strapped to building. Sticks about
16 ft
above roof peak. Contractor charged $48,000 for this. This is tower only,
no
antennas or feedlines. Big cement base, huge strap to side of building. I
just
laughed. I would have done it for them for under $2K. But, the owners said
that
"no way a $2K mast can compare with a $48k one." Coverage is pitiful. My
$2k
mast would have had pretty much the same pitiful coverage, but still, you
can
do a lot with the leftover $46k.


Put it in the middle of the roof! Best location. Reduces wind oscillations
and shocks.
A beam will not change tuning as it turns. Looks very workmanlike.


AL7X

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1bRe: Metal Roofs and Hex-Beams
<https://groups.yahoo.com/neo/groups/hex-beam/conversations/topics/18506;_ylc=X3oDMTJycGI1c2xuBF9TAzk3MzU5NzE1BGdycElkAzQ0NTUxNTMEZ3Jwc3BJZAMxNzA1MDYzMTA4BG1zZ0lkAzE4NTA2BHNlYwNkbXNnBHNsawN2bXNnBHN0aW1lAzE1NTk0NDUyMDI->
Sat Jun 1, 2019 6:19 pm (PDT) . Posted by:"BG" ko6hl at sbcglobal.net
<ko6hl at sbcglobal.net?subject=Re%3A%20Metal%20Roofs%20and%20Hex-Beams>
J

From: hex-beam at yahoogroups.com [mailto:hex-beam at yahoogroups.com]
Sent: Saturday, June 01, 2019 6:06 PM
To: hex-beam at yahoogroups.com
Subject: [hex-beam] Re: Metal Roofs and Hex-Beams

I was in the commercial radio business for years. I found out that any type
of mast that lays along a building and sticks up past the roof is a waste
of time and money. Here is what works.

Put a hinge in the center of the roof. Barndoor hinges are fine.

Bolt or weld a pipe flange to one leg of the hinge.

Put a 21 ft 2" or 1.5" galvanized water pipe.

Put a guy wire ring about 70% or 80% of the way up. Muffler clamp to
prevent sliding down.

Use 4 guy wires.

Lay the pipe down over the edge of the roof. On peaked roofs, I use the
eave.

Set two guys along the roof peak.

Stand antenna up and set and adjust the two guys going to the eave.

You could calculate or guess these last two wires.

The antenna stands up easily, pulling against one of the eave wires.

Fasten the other eave wire.

Voila, 21 ft above the roof.

You can extend the 2" pipe with smaller pipe. 1.5" is a good fit.

I suggest you weld any extensions, as threaded fittings can crack.

If you go taller than the 21', or with big antennas, you may need two set
of guys.

Make sure the guys are not 1/2 1/3 or 1/4 of the distance from the ends. It
sets up

mechanical resonances. I once had one of these pipes guyed at the middle
and it danced

like a hula belly dancer. Moved the ring up a few feet, presto!

Guy wires should NOT be humming tight. It is ok if the pipe top sways a
foot or so.

As the guy comes up against the wind, motion is dampened. Lot less stress
that way.

I have one here downtown Nome, not in use but still standing, Since 1982.

By the way ... I suggest no less than 3/16 guy wire. The smaller one will
break

due to electrolysis or galvanic corrosion. I looped my wires t! hru
thimbles, and the

break was at the peak of the thimble. That was with 1/8 wire. Inspection
showed

like burning of the wire at this point.

Roof guy anchors should be BOLTED not lagged. Pipe hinge can be lagged as

the forces are perfectly downwards.

I prefer forged eye bolts for guys. The ones that are just bent into a loop
have a

tendency to open up unless they are Bejesus strong. Like 3/8 minimum. The
pull

of wires is relentless. You can also weld the gap closed on open ones. But
welds

here like to corrode.

Always bring all feedlines to the hinge, then away. Never, ever from
mid-pipe.

It helps to have a barrel coax connector at the hing area in case something
has

to be troubleshot or replaced. For professional work, the feedline can
often be

inside the mast, and then in conduit from the hinge to the radio.

There is an cell tower here. Rohn 55G. Strapped to building. Sticks about
16 ft

above roof peak. Contractor charged $48,000 for this. This is tower only, no

antennas or feedlines. Big cement base, huge strap to side of building. I
just

laughed. I would have done it for them for under $2K. But, the owners said
that

"no way a $2K mast can compare with a $48k one." Coverage is pitiful. My $2k

mast would have had pretty much the same pitiful coverage, but still, you
can

do a lot with the leftover $46k.

Put it in the middle of the roof! Best location. Reduces wind oscillations
and shocks.

A beam will not change tuning as it turns. Looks very workmanlike.

AL7X
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