Post all the pictures you want on towertalk@groups.io
73, Jim W7RY
On 11/14/2022 10:25 AM, Grant Saviers wrote:
Resent w/o pictures per K7LXC request, contact me off list if wanted.
-------- Forwarded Message --------
Subject: Re: [TowerTalk] TIC-Ring Question
Date: Fri, 11 Nov 2022 11:10:15 -0800
From: Grant Saviers <grants2@pacbell.net>
To: towertalk@contesting.com
Hi Dave,
Re limit switches, I had to fabricate limit switches for the K0XG
rings on my Rohn 65 tower. 7 rings. The mount has the switches on
the tower leg, and the ring uses a 3x3x1/8 6061 angle plate and a
delrin block to actuate the IP65 Honeywell microswitches. I don't
recall why I used IP65 vs IP67.
I was willing to sacrifice about 30 degrees of due south pointing to
not have to have overtravel in the switch assembly, since each switch
has some deadband. That simplified things a bit, with hardly any DX
(except HC8!) in due south from WWA.
It took a bit of cut and try to get the distance from switch roller to
actuator plate trip point correct by modifying the thickness of the
plastic block or the offset from the tower leg (I think what is shown
in the pictures). One constraint is the actuating block has to rotate
without interference.
The switches are Honeywell IP65 from the picture. They are on the
underside of the mounting plate. I think I replaced one (of 14) in
the past 6 years, but it measured ok. The switches go to a j-box with
diodes so the ring can be reversed off limit. One diode failure also.
My plan is limit switches are last resort if the RT21 programmed
limits are off.
I did have to change the ring centering cam rollers from factory to
get the ring and pinion gears to fully engage and haven't observed any
jumps, but that is not proof it hasn't happened a small amount. The
top ring @140ft is 3L 48ft boom 40m full size.
What I learned:
Use much larger diodes - the K0XG motors are 180v DC PWM driven and it
is difficult to find 1kv 10a diodes that are not stud mounted so I did
the best I could. Also, use TVS protection since it might be full
motor voltage/current being interrupted.
Put a high value resistor across the switch contacts so bad switch,
wiring, or bad diode can be analyzed from the shack, if one can't
reverse out of a limit.
Clearly mark the inside of the j-box with wiring and part orientation
and photograph it. Most tower climbers aren't EE's.
Waterproof plastic j-boxes aren't, so always have a smaller than bug
size drain hole at the low point. Maybe 50" of rain here per year. ;(
Use 6x6 rather than 4x4 j-boxes.
I like the idea of a back-up magnetic azimuth sensor, looked a bit at
them but wondered how they would work among all the steel and RF.
73,
Grant KZ1W
On 11/11/2022 10:11, Leeson wrote:
I've been using a TIC ring rotator here on a big 7el 10m Yagi for the
past 20 years with good success, but it has a couple of well-known
unresolved problems: In the high winds we have on our hilltop (147
mi/h 3s gust measured), it can jump a tooth on the motor or pot gear,
which eventually makes the direction indicator pot totally out of
sync, or even damages it. Since the ring rotor doesn't have physical
limit switches, that has permitted over-rotation that parts the coax.
Re direction indication, has anyone had any success with alternatives
such as magnetic or microswitch gear tooth counters? Or a simple
compass module with output that a Green Heron RT-21 can read (0-5
volts)? See G6EJD, KJ4JJH, K3NG. I'd like to have direction
indication that mounts directly at the ring or antenna boom itself,
rather than through a coupled gear. and it should work at zero speed.
Second, has anyone had success with adding waterproof (IP67) limit
switches? Honeywell, Omron, IP67 microswitches or cheaper imports? If
a magnetic gear tooth sensor is used, what kind of spacing precision
is required? With 360 teeth, the 1° precision should be plenty for HF.
I am aware of modifications and updates (e.g., N1CX) that may help
prevent gear tooth skipping, but I want something bullet-proof that
really gives me full confidence. Even a partial failure in a contest
can compromise an otherwise winning effort; in our big HC8 station,
we gave up on rotators and went with multiple antennas per band. But
for my less complex setup here at home, I intend to try to resolve
both of these problems when the weather permits, and am interested in
hearing the experiences of list folks.
BTW, I resolved the climb-over issue with a small 3-rung steel ladder
mounted below it on the tower face. And if the limit switches work
out, I'll add them to my prop pitches, as well.
Thanks, Dave W6NL/HC8L
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Thanks and 73, Jim W7RY
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