Hello T-Ters;
Anyone out there, besides myself, using an old HyGain
RBX-5 antenna rotator? For those of you that are not
familiar with this unit, the RBX-5 is a very LARGE
commercial-type rotator that was made by HyGain many
years ago.
I don't know the age of my unit; I purchased it used from
AES in Milwaukee. It was being sold "on consignment." I
did call Telex-HyGain after I had bought it and was told
that due to the age of the unit, they had NO information
on that model. HyGain did send me some information on a
model 3501DA, which seems to have the same physical
appearances as my RBX-5 unit.
My RBX-5 (and the 3501DA) is so large that it will not
fit inside of a Rohn 45, 55 or 65 tower. The unit is 19"
wide, 24" long and about 15" high. I am guessing that my
RBX-5 weighs somewhere between 150 and 175 pounds.
In order to mount my RBX-5 to my Rohn 45 tower, I had
a "mounting shelf" fabricated from 2" x 2" x 1/4" angle iron
and used a quantity of 6 - 3/8" u-bolts to hold the shelf to
my tower.
For a direction indication system, my RBX-5 came with
a oval-shaped control box that had a compass scale on
it and a disc that moved around, to indicate degrees of
the compass. A pair of Bendix selsyns were used in this
system - they appeared to be World War II surplus units.
After I had installed my RBX-5, I found that the selsyns
would not stay in calibration. I spoke with an electrical
engineer, who was also employed at the factory where I
was working, and told him I could not keep the selsyns in
calibration. At that time, I knew nothing about selsyns.
The engineer sat me down and gave me a litle "education"
in the theory and application of selsyn motors. He told me
that since my selsyns were of the 400-cycle variety and be-
cause I had a conductor length of approximately 250' that
connected the two units, they would not stay calibrated.
After I learned about this, I tried to compensate for the
long conductor run by increasing the size of the wire that
connected the selsyns. That did not help so I resorted to
putting a 2" wide by 24" long piece of reflective tape on
the underside of the boom of my antenna, on the forward
side of the boom to mast plate. That way, I could shine a
spotlight at it (during darkness) and see in which direction
it was aimed.
Running outside in the garage and pointing a spotlight at
the antenna at night got to be very old, very quick. It was
especially tiresome to do this in the middle of winter! I
kept thinking about what I might be able to use for a more
practical direction indication system.
After being layed off from the factory where I had been
employed for 19 years, I started working for a company
that manufactured truck frames for General Motors. The
company had 3 production lines and in some of the welding
fixtures, they used ABB robots that were mounted on a
gantry. At one time, someone had installed some Namco
programmable limit switches, for the purpose of indicating
on the gantry where the robot was (7th axis movement of
the robot).
These Namco programmable limit switches had a very nice
3-digit LED control box and they had been removed from
service. They were basically sitting there, doing nothing. I
found that these Namco units used a small resolver motor
that was mounted inside of a worm gear reduction unit, for
position indication.
I kept looking at these unused Namco units and thought
that if they were once used to indicate the 7th axis position
for the robot, maybe they would be able to be used as a
position indicator for my rotator.
I removed one of the resolver motor gear reduction units
from a robot and found a spare Namco controller. After
hooking them up, I found that the unit would "count up"
from 0 to some number (I think it was 815 that it counted
up to). It took many revolutions of the shaft of the worm
gear reduction unit to allow the controller to count up
through the number range for which it was programmed.
I then took the little resolver motor out of the reduction unit
and found that it would count through the range simply by
rotating the shaft of the resolver motor one revolution. Being
unfamiliar with these Namco units, I called their toll-free
telephone number and spoke with a Customer Service
engineer and told him that I was wondering if it was at all
possible to use the system as a direction indication system
for an antenna rotator.
He started to laugh and told me that it was indeed possible;
he informed me that I was attempting to use a $2,000+
unit for my application. He then told me how to re-program
the "scale" so that it would count from 0 to 359 (the degrees
of the compass). I thanked him for the information and then
started to figure out a way of mounting the little resolver
motor in my rotator, in place of the 400-cycle selsyn motor.
Since my rotator was about 250' away from my control
box location, the first thing that I did was to find some
3-pair cable and see if the system would work with a 250'
cable distance. I found that it would work just fine with
that much cable connecting the resolver to the control box.
I then figured out a way of mounting the little resolver motor
in my rotator, in place of the 400-cycle selsyn motor. After
mounting the reslover motor and running the new 3-pair
individually-shielded cable, it worked great. I now have a
direction indicating system that will display my beam heading
and indicate the direction in degrees of the compass!
This system has worked very well in the few years that I
have been using it. I did have a resolver motor that was
damaged by lightning but I had a spare unit and replaced
it. It has been working just fine ever since. No more trips
out to the garage in the winter time and shining a spotlight
up at the antenna, to see in which direction it's aimed!
73 de Brad, N9EN @ Radio Free Roscoe (IL)...
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