From:
Fred Hopengarten K1VR 781/259-0088
Six Willarch Road
Lincoln, MA 01773-5105
permanent e-mail address: fhopengarten@mba1972.hbs.edu
On Sun, 9 Aug 1998 19:28:21 EDT W9zr@aol.com writes:
>
>I would like to sidemount a small beam on Rohn 45. Can anyone give
>me some
>advice on how to proceed? Is there a commercial unit available?
>
>73 Randy
The Sidemount Collection
by Fred Hopengarten K1VR
I've been saving occasional remarks on sidemounts. I
keep remarks on the TIC RingRotor in a separate file. Ask
for that separately, if you'd like to see it. I have a
Leesonized (ruggedized) Cushcraft 40-2CD on a TIC RingRotor,
and love it. I also have a TH6DXX on a homebrew sidemount
which looks like a swinging gate (a phrase which I believe
that I originally coined in around 1986 when it first went
up). The swinging gate and rotator was one-third the price
of the TIC RingRotor, but the local ham with the machine
shop who could thread the water pipe, and so forth, took
some care and feeding.
===========================================
[From 1997, I think]
I have one RTS rotating tower and one with a TIC ring
rotator. I'm satisfied with both.
Re the RTS setup, I would recommend using at least two ring
bearings (my setup has only one above the rotator, and it
would fall if one guy failed - however, it has survived 134
mi/h fastest mile winds). I plan to switch to double guys
on the ring bearing. If you order the RTS setup, you might
want to see if you can talk Dick into drilling drain holes
in the tower leg stubs in the base bearing, so the legs can
drain more easily than just hoping they will drain at the
circumference of the stubs. Otherwise all first class.
As a practical matter, there is a good-news/bad-news element
of the rotating tower choice. The antennas are always in
the same relative position to each other, so you don't get
odd effects of resonant booms or the like when antennas are
in different directions. On the other hand, most contesters
find they benefit more from being able to "spray" in two
directions at once, and the rotating tower doesn't do this
readily.
If you go the RTS route, I would give serious consideration
to putting the rotator at the ground level, even though that
adds to the cost of the ring bearings. This gives you
guying redundancy, so you can sleep at night. There's no
question about the generous engineering margins on the ring
bearings, but they are really heavy to wrestle on the tower
and tough to climb around or stand in when working. As a
last caution (don't laugh, it happens!), the ring bearings
are easy to bang your front teeth on if you aren't careful.
And they are SOLID STEEL, so guess what would give way.
The TIC rotator is not as conservative in it's engineering,
but mine has worked well. I have two motors, and short them
for braking when not rotating. The offset is a bit of an
additional wind problem, but the 50' boom hasn't been a
problem. The ring rotator is also hard to climb around, so
outfit your belt with auxiliary Gorilla Hooks (I use
aircraft control cable, NICO clamps installed with proper
tool, and REI spring-release caribiners, one on each side of
the belt in the D-loops, in addition to the standard
halyard).
For the future, I'm giving more thought to fixed antennas
(that is, to orienting the towers at installation to get the
sides aimed in the right directions for EU, JA and US), as
well as simple side mounts without the extensions to get 120
degree rotation. The problem to be solved for that setup is
a simple limit switch arrangement, but the bearings and
rotators are simpler and I just don't think the need is
there on side mount antennas for any more rotating range.
There is an N2TR side mount used at, for example, the W2SX/1
VHF setups that is simple and inexpensive. It is
essentially two crossed aluminum or galvanized steel
angles, bolted to adjacent sides of the tower, crossing at
the apex tower leg and continuing so as to mount a rotator
plate or mast bearing. One angle is mounted with the
vertical face down, the other with the vertical face up,
they are bolted at the overlap.
You can sketch this to see how it would work.
Dave Leeson, W6NL (ex-W6QHS)
====================================================
From: "Fatchett, Mike" <Fatchett.Mike@tci.com>
To: <towertalk@contesting.com>
Date: 30 Jul 1998
Force12 was selling a sidemount as well. I don't recall any
of the detail. I think it sold for about $180.00
Mike W0MU
========================================
From: k4sqr@juno.com (Jim MILLER)
To: <towertalk@contesting.com>
Date: 30 Jul 1998
Check Antenna Mart sidemounts; very rugged & permits 300
degree rotation. They are at Max Gain Systems web page.
www.aaow.com/mgs/antenna.htm
Jim, K4SQR
=================================
From: "Jim White, K4OJ" <k4oj@ij.net>
To: <towertalk@contesting.com>
Date: 31 Jul 1998
There are lots of approaches out there....one which is
inexpensive, and sure seems to work is one that:
K4XS has used, it is a very basic mount - he has used it for
years. Judging by the number of rotor boxes in his shack I
would say it must work OK. The Italian ham magazine once
ran a picture of Bill's old shack and the translation under
the picture (loosely) was - "no, he does not sell rotator
control boxes".
The 'XS Sidemount:
Imagine the tower has three legs: A, B & C.
Bill uses one piece of right angle stock and u-bolts it to
two legs of the tower - this is mounted with the side of the
stock parallel to the ground being on the top, lets it is
attached to legs A&B......
He then uses another piece which he mounts onto legs B&C
slightly above the other piece. This time the side of the
stock parallel to the ground is on the bottom.
These two pieces are at slightly different altitudes - they
do not quite touch each other. The actually extend past leg
B and the two angles form a V coming off the side of the
tower. The point of the V is at outside of leg B.
The V then has a triangular plate of aluminum mounted to
both of the angles, which are spaced apart (that altitude
thing) by - you guessed it - the thickness of that plate.
Now imagine two of these things. They are mounted several
feet apart. The lower on acts as the shelf for the rotator.
The upper one has a hole through it with a PVC fitting in it
to act as a bushing/bearing. An upside down J made of
galvanized water pipe passes through the upper plate's
bearing and into the rotor. Voila.
By making the upside down J have its horizontal component
longer than the distance from the center of the rotor to the
far side of leg A or C, you have the same effect as the
commercial "Swinging Gates"....no, that is not the new rock
group from Microsoft.
This length allows for the boom, when mounted at right
angles (when viewed from above/below) to the horizontal part
of the "J" to travel about the tower for approximately 300
degrees of rotation before the tower gets in the way again.
A dead spot in the SW quadrant for NA hams should be fine.
You can still catch your Pacific OK and not hamper SA path.
It works. Though the picture is not zoomed in you can see
what Bill has been up to during his Summer break from
teaching at the Florida Contest Group website, or go
directly to:
http://www.4w.com/deemer/k4xs.htm
(Yup.....Bill is back)
Jim, K4OJ
==============================================
From: "Jim White, K4OJ" <k4oj@ij.net>
To: <towertalk@contesting.com>
Date: 31 Jul 1998
Subject: Re: [TowerTalk] The best sidemount
The J is upside down, and in some instances it is a
U....depending on what end height was needed and what
clearances were necessary for guy wires, etc. Most of them
seem to have been with the long end of the J into the rotor.
Jim, K4OJ
====================================================
From: K7LXC@aol.com
To: <towertalk@contesting.com>
Date: 31 Jul 1998
In a message dated 98-07-30 13:40:58 EDT,
n4zr@contesting.com writes:
<< I've perused the archives without success, and am now
looking for advice from Towertalkians on who makes good
sidemounts for Rohn 25. I need to mount a small tribander,
and would like to have more than the 230 degrees or so of
rotation that a basic sidemount would give, which probably
means I'll need the swinging-gate type. IIX gets almost
$200 for theirs, though, and it appears to mount on only one
leg. That seems iffy to me. >>
It's fine for the aforementioned 'small tribander'.
Works for a TH7 sized antenna too.
Steve K7LXC
Champion Radio Products
www.championradio.com
=============================================
From: W7NN@aol.com
To: <towertalk@contesting.com>
Date: 31 Jul 1998
At the W7RM Mega Station, Rush uses several side mounts for
the stacked beams. A good photo of the construction of
these home brew units is on the web page at
http://members.aol.com/w7nn
Ron
HamStuff by W7NN
QSL Systems and Contest Aids
=====================================================
From: "Robert W5AJ" <w5robert@blkbox.com>
To: <towertalk@contesting.com>
Date: 1 Aug 1998
Subject: [TowerTalk] http://www.aaow.com/mgs/antenna.htm
(AntennaMart)
http://www.aaow.com/mgs/antenna.htm
Best I can tell this is the web page with the Antenna Mart
side mount.
Robert W5AJ
============================================================
From: "Gary E. Jones, Ph.D." <gejones@whale.otr.usm.edu>
To: <towertalk@contesting.com>
Date: 2 Aug 1998
Subject: Multiple antennas and Swing Arm Design
Well, my QTH is 70 miles north of the Gulf of Mexico in
Mississippi (part of Hurricane Alley). I have had a three
yagi 100' stick of Rohn 45 and a two yagi 78' stick of Rohn
25 up through Hurricane Frederick... sustained winds in
Hattiesburg were in excess of 80 MPH. Lodge pole pine trees
(60-70') were down everywhere and snapped off in the middle.
All my yagis and towers made it through without a scratch.
All yagis are heavy duty or stock.
Now, my current Rohn 45 has the 2 element 40, over the 5
element 20, with the swing arm with a 5 element 15 and 5
element 20 in a 20 meter 5 over 5 stack configuration 15M =
65" and 20M at 55') and the Th6 at about 35 feet.
The TH6 sits at the first set of guys. It has also been
through very high wind storms with no problems. The one
hurricane we have had since this has been up gave us gusts
into 60 - 80 MPH with nary a problem.
Obviously, I try to do things right. And, the difference
between Rohn 45 and Rohn 25 is a rather substantial
difference. I use Rohn guy brackets at all locations, and
torque arms, and 1/4" EHS all around. Rohn 45 can take a lot
more load than 25.
My big swing arm (12' with 2 big yagis on it) sits right on
top of the set of guys at 50'. The swing arm uses 2" angle
iron across two faces of the tower, vertical legs 1 and 2 on
the bottom of the arm, and vertical legs 2 and 3 on the top
of the swing arm. The arm is made of 1 1/2" schedule 40
water pipe with a cross brace in the center (cold
galvanized... wish it was hot dipped). I will try to draw a
diagram of it below. I have never doubted that this tower is
going to stay up... it is rock solid. The swing arms are
twisted with HAM-IVs and there is a TB-3 thrust bearing at
the top of the swing arm to take all the lateral torque of
the swing arm and the dead weight of the swing arm and the
antennas if the rotor needs to be replaced.
My new tower will be 140' of Rohn 45 with a 5 element 15
monobander at the top (150'), 2 element 30/ 2 element 40
(shortened) FORCE-12 duo-band yagi at 140' at the top of the
tower, a 12' swing arm at 70-80' with a 5 element 12 meter
(Hygain) at 80' and a 5 element 10 meter (Hygain) at 70' and
at 40' on a single antenna swing arm will be a 5 element 17
meter monobander (Hygain). My belief is that the yagis will
go long before the tower is in trouble.
Diagram of the 12' swing arm...
______________ Thrust Bearing (TB-3)
-----------|| 2" angle iron
||______________
|-------------|
|| // ||
|| // ||
|| // ||
|| // ||
|| // ||
|| // ||
|| // ||
|| // ||
|| // ||
||// ||
||/ || swing arm itself
||\\ ||
|| \\ ||
|| \\ ||
|| \\ ||
|| \\ ||
|| \\ ||
|| \\ ||
|| \\ ||
|| \\ ||
|| \\ ||
|| \\||
||___________\||
||--------------
||
||
||
/ \
| | Rotor
| |
|___|________________ 2" angle iron
--------------------
That should give you a good idea of what they look like.
Gary W5FI
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