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A underlying thread, low tower heights, seems to exist in quite a few
of the latest posts, so I thought I would throw this in.
Also, LB mentioned the difficulty in getting a dipole as high as
possible with a Quad.
I originally had this published back in the 60's in HR, but that version
is nowhere near as strong
as this one.
Anyway, ( and it is in use here now ) a good way to hang a dipole well
above any mounted
rotateable antenna is the use of an extension mast. It's pretty simple
to make, and works like
a charm. Basically, it is another mast joined to the top of your
existing mast.
Details of mine. I use a molly be damned 24 footer I got from TT for my
main mast. About
8 feet of it is inside the tower. I had a 14' 1/4 wall aluminum mast,
and just happened one day
to come across a solid 61T6 rod? about 30 inches long. I had a local
machine shop turn 1/2 of
it to fit into the molly mast, and the other half machined for the 1/4"
wall 14 footer.
Pause now for a short commercial. The molly masts are hot dipped
galvanized and leave quite
a few burrs on the inside. You will need to clean this out. The method I
used is to get a brake cylinder hone from a auto local supply, and run
it up into the inside of the molly. You can use a drill extension to get
the necessary depth, and it will really clean off the inside walls. (
incidentally, I use a small version to clean the inside walls of tubing
when building a new beam from the junk pile ) Do the same thing to the
inside of the aluminum mast. What you want to end up with is a good
tight fit.
In my case, the machine shop did it exactly like I wanted ( 0 tolerance
) and I had a devil of a
time fitting the machined rod into the molly mast. Final solution was to
buy some dry ice and
pack it around the machined rod. Left it there for a couple of hours (
used a large plastic ice
chest ) and then removed it. Be careful here, you don't want to touch
that thing with bare hands. I wore mittens covered with a pair of heavy
work gloves. Anyway, at this point, the rod
would barely go into the molly for a few inches, so I secured the other
end of the mast, and
hammered it the rest of the way. Now I just filed off the other end,
checked the fit again, and
it was ready to go. .
You haven't lived until you try to seat a 24' mast weighing about 130
pounds. My solution was
to cut a tower brace and inset the sucker from the ground into the
tower, then rigged the gin
pole line down through the tower. From there, my Kobota tractor made
short shift of lifting it.
OK, once the thing is at the top, and the solid rod is completely
sticking out of the tower top a few inches, Bring the 1/4' wall mast to
the top and mate the two. I used two 2" muffler clamps
around the aluminum mast part to secure it. Oh yes, almost
forgot,....before you mount the aluminum mast, place a thrust bearing (
good type ) about a foot down from the high end, and secure it to the
mast with the bolt in the sleeve. Then hang a couple of small, but good
pulleys
to 2 of the outer holes in the thrust bearing. I use holes 90 degrees
apart, and use those little
race track links to secure the pulleys. Rig a double length of good
line through the pulleys.
The length you will need is that length which will be sticking out the
top of the towers. In my
case here, a total of 2 52' lengths. ( 16' molly out the top + 14'
aluminum mast = 26x2 = 52. )
OK, thrust bearing in place, pulleys in place, and lines threaded. Now
take it to the top and seat
it.
And if you don't want to waste anything, mount a 2 meter antenna on the
very top. I use a
14' Diamond. My original tower was 105' tall, plus the 26' and then the
diamond which put the
tip of it at 145'.
Of course, another method of mounting the aluminum mast is to lower the
molly de damned
(in my case) through the rotor place about 16 feet or so, throughly
secure it in place, and then stick the aluminum mast down the center of
the tower.
OK, raise the who she-bang, mount the rotor, secure the mast ( and don't
break your hand
doing it like I did...) and we are left with 26' of mast sticking out of
the top. The ends of the
lines threaded through the pulley ( you did remember to tie them
together didn't you ? ) are
dangling right at the top of the tower. Make your dipole, or whatever,
and tie the end of one
of the lines to the balun and hoist it up. Same thing with the other
line.
Secure the other ends of the dipoles and you're in business. Of course,
there are several
variations of how you can build this, but this version is "stand alone"
and is strong. Don't mess
around with water pipe or such on a project like this. Two 1/4 wall
aluminum masts would
probably work just as well.
And for God's sake, don't climb this mast above the junction!!!, and if
you use aluminum masts, don't climb it period!. It's harder to lower
the whole thing to mount an
a Christmas tree, and takes more time, but you can always do that as you
raise the thing.
How strong is it? A lot more than necessary, and it doesn't need the
dipole wires for guying.
Good way to hang 4 slopers....Want to change the antenna? Just climb to
the top and lower
the dipole, replace it, and back up again. So, the rotor turns the mast,
and the thrust bearing
rotates freely at the top.
Hope this helps. First time I ever had an 80 meter job at 1/2 wave, and
believe me, it played!
73
Ed
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<HTML>
A underlying thread, low tower heights, seems to exist in quite a
few of the latest posts, so I thought I would throw this in.
<P>Also, LB mentioned the difficulty in getting a dipole as high
as possible with a Quad.
<P>I originally had this published back in the 60's in HR, but that version
is nowhere near as strong
<BR>as this one.
<P>Anyway, ( and it is in use here now ) a good way to hang a dipole well
above any mounted
<BR>rotateable antenna is the use of an extension mast. It's pretty simple
to make, and works like
<BR>a charm. Basically, it is another mast joined to the top of your existing
mast.
<P>Details of mine. I use a molly be damned 24 footer I got from TT for
my main mast. About
<BR>8 feet of it is inside the tower. I had a 14' 1/4 wall aluminum mast,
and just happened one day
<BR>to come across a solid 61T6 rod? about 30 inches long. I had a local
machine shop turn 1/2 of
<BR>it to fit into the molly mast, and the other half machined for the
1/4" wall 14 footer.
<P>Pause now for a short commercial. The molly masts are hot dipped galvanized
and leave quite
<BR>a few burrs on the inside. You will need to clean this out. The method
I used is to get a brake cylinder hone from a auto local supply, and run
it up into the inside of the molly. You can use a drill extension to get
the necessary depth, and it will really clean off the inside walls. (
incidentally,
I use a small version to clean the inside walls of tubing when building
a new beam from the junk pile ) Do the same thing to the inside of the
aluminum mast. What you want to end up with is a good tight fit.
<P>In my case, the machine shop did it exactly like I wanted ( 0 tolerance
) and I had a devil of a
<BR>time fitting the machined rod into the molly mast. Final solution was
to buy some dry ice and
<BR>pack it around the machined rod. Left it there for a couple of hours
( used a large plastic ice
<BR>chest ) and then removed it. Be careful here, you don't want to touch
that thing with bare hands. I wore mittens covered with a pair of heavy
work gloves. Anyway, at this point, the rod
<BR>would barely go into the molly for a few inches, so I secured the other
end of the mast, and
<BR>hammered it the rest of the way. Now I just filed off the other end,
checked the fit again, and
<BR>it was ready to go. .
<P>You haven't lived until you try to seat a 24' mast weighing about 130
pounds. My solution was
<BR>to cut a tower brace and inset the sucker from the ground into the
tower, then rigged the gin
<BR>pole line down through the tower. From there, my Kobota tractor made
short shift of lifting it.
<P>OK, once the thing is at the top, and the solid rod is completely sticking
out of the tower top a few inches, Bring the 1/4' wall mast to the top
and mate the two. I used two 2" muffler clamps
<BR>around the aluminum mast part to secure it. Oh yes, almost
forgot,....<U>before</U>
you mount the aluminum mast, place a thrust bearing ( good type ) about
a foot down from the high end, and secure it to the mast with the bolt
in the sleeve. Then hang a couple of small, but good pulleys
<BR>to 2 of the outer holes in the thrust bearing. I use holes 90 degrees
apart, and use those little
<BR>race track links to secure the pulleys. Rig a <B><U>double </U></B>
length of good line through the pulleys.
<BR>The length you will need is that length which will be sticking out
the top of the towers. In my
<BR>case here, a total of 2 52' lengths. ( 16' molly out the top + 14'
aluminum mast = 26x2 = 52. )
<P>OK, thrust bearing in place, pulleys in place, and lines threaded. Now
take it to the top and seat
<BR>it.
<P>And if you don't want to waste anything, mount a 2 meter antenna on
the very top. I use a
<BR>14' Diamond. My original tower was 105' tall, plus the 26' and then
the diamond which put the
<BR>tip of it at 145'.
<P>Of course, another method of mounting the aluminum mast is to lower
the molly de damned
<BR>(in my case) through the rotor place about 16 feet or so, <B><U>throughly
secure it in place, </U></B>and then stick the aluminum mast down the center
of the tower.
<P>OK, raise the who she-bang, mount the rotor, secure the mast ( and don't
break your hand
<BR>doing it like I did...) and we are left with 26' of mast sticking out
of the top. The ends of the
<BR>lines threaded through the pulley ( you did remember to tie them together
didn't you ? ) are
<BR>dangling right at the top of the tower. Make your dipole, or whatever,
and tie the end of one
<BR>of the lines to the balun and hoist it up. Same thing with the other
line.
<P>Secure the other ends of the dipoles and you're in business. Of course,
there are several
<BR>variations of how you can build this, but this version is "stand alone"
and is strong. Don't mess
<BR>around with water pipe or such on a project like this. Two 1/4 wall
aluminum masts would
<BR>probably work just as well.
<P><B><U>And for God's sake, don't climb this mast above the junction!!!,
and if you use aluminum masts, don't climb it period!. </U></B> It's
harder to lower the whole thing to mount an
<BR>a Christmas tree, and takes more time, but you can always do that as
you raise the thing.<B><U></U></B>
<P>How strong is it? A lot more than necessary, and it doesn't need the
dipole wires for guying.
<BR>Good way to hang 4 slopers....Want to change the antenna? Just climb
to the top and lower
<BR>the dipole, replace it, and back up again. So, the rotor turns the
mast, and the thrust bearing
<BR>rotates freely at the top.
<P>Hope this helps. First time I ever had an 80 meter job at 1/2 wave,
and believe me, it played!
<P>73
<P>Ed
<BR>
<BR> </HTML>
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