[Antennas] Need good idea for chimney mount.

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OM,

My advice from 15 years' experience putting up TV antennae:


Find your Channel Master dealer.  They make a "triple rivet" chimney
mount that

has stainless steel straps.  The brackets that fit onto the chimney are
heavily

galvanized.  Expect to pay at least $75 retail.  The identification for
the CM mount

is that there are 3 rivets about 3/8" holding the bracket together and
the bracket

was galvanized after being riveted.  Silvery-grey colour.  Putrid
yellow-green

colour indicates a cheapie chromate finish.  Make sure you get stainless
steel

straps.  Galvanized straps are thinner, made of weaker steel and if you
listen

carefully, you can hear them rusting.......HI!

Or, you may find such an item at a hamfest.  There is also an RCA mount
that is

pretty ferocious.  It is designed to have a single strap so you will need
a pair.

If you can anchor the bottom of the mast to the roof (Channel Master has
a chromate-

plated, variable angle clamp that is similiar to Radio Schlock 15-888)
please do so as

it will reduce the bending forces on the mast.  It will also provide
another anchor

to resist torque.  If you can use this roof anchor, drill through the
mast and "pin"

the mast.  The brackets on the chimney mount the mast hold by friction
and have a 

very limited ability to resist the large torque moments of a beam.  


Misc tips:

Mount the mast and mount such that you can work on it from the roof. 
Having 

the elements a foot or two closer to the house will not matter much.

Use lockwashers under every nut.  Loctite in addition if you wish.

For mast material, use 1" galvanized water pipe.  Much stronger than TV
masting.

There is a "trick" to putting the stap clamps on the triangular-shaped
"eyebolts."

Should you choose to go with the Channel Master mount, drop me a note and
I'll

go into it........the procedure is too detailed to go into now.  Or get
the sales human

at the store to show you.

Save the remaining stainless steel strap material.  It is made from some
manner 

of high-strength steel and comes in handy around the house.

Note that the straps may have razor-sharp edges, wear gloves.

When you call around to find a chimney mount, try to locate "corner
guards" which

used to be made by "South River."  These are little diamond-shaped
aluminum 

clips which distribute the clamping forces of the straps and reduce the
tendency

of the straps to "dig into" the bricks or cinder block chimney.  Also,
they help keep

the sharp edges of bricks from weakening the straps.


Grounding.

Find out what your local electrical code says and follow it to the
letter.

Your insurance company may resist paying a claim if the grounding is not
to code.


Rotor.

A standard TV rotor will not last long spinning anything much larger than
an TV

antenna.  The dead weight (20 lbs) is much more than a typical TV antenna
but the

real problem is torque.  TV rotors generally have either sintered powder
(junk) or

die cast (REAL junk) gears to keep costs down.  Even the "heavy duty" TV
rotors

have stamped steel gears.   None of the TV rotors have a  braking system.

Buy a Ham-M or some variant.


By the way, "firebrick" is spot on in his comments.  I was very reluctant
to do 

chimney mounts for the reasons he mentioned.  There were times, however,

(like slate roofs or customer insistance) when I had to use a chimney
mount.

73,

Tim  K3HX

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