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Author Topic: Channel Master Rotor  (Read 756 times)
KA3NXN
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« on: March 20, 2006, 06:02:58 AM »

Does anybody know how to calibrate one of these rotors? It is the $59.00 type that Lowes & radio shack sold a while back. I set mine correctly before I put it up now after turning it a few times it is out of whack. When the indicator on the box points north the antennas are pointed NE. If I play with it for a bit, and then go back an point it north again, the antenas may be pointed NW. I don't see how this can be calibrated at all. It may just be a throw away and buy a new one.

Suggestions?Huh?
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K7UNZ
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« Reply #1 on: March 20, 2006, 06:30:20 AM »

You have to keep in mind that these were designed to handle TV antennas, and are not made to stop on a dime.  

It uses a disk brake system, which does not lock, and some overshoot is to be expected.  In fact, in a high wind location, the antenna will turn just due to the force of the wind.

If it's been turning some kind of ham antenna over the years, it's possible that the brake is simply worn-out.

Your cheapest route is to replace the unit with a new one.

I turned a HQ-1 Mini-Quad with one of these for 3 years in Norway, and a few more in Italy, and had no significant problem even after some "crisp" Nordic winters.

However, the price alone will tell you that they are not designed to last forever.

Jim/k7unz
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KG4RUL
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« Reply #2 on: March 20, 2006, 06:50:41 AM »

I think that if you rotate it fully to one stop and then back to the other, it will self-calibrate.  

The main problem with these rotators is that their gear train is simple spur gears which are not inherenty locking like worm gear drives.  Thus, wind loads can cause the whole system to rotate when no power is applied and thereby lose the calibration.  That is the reason that high end rotators have electrically actuated, mechanical brakes.

Dennis KG4RUL
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KC8VWM
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« Reply #3 on: March 20, 2006, 07:41:15 AM »


Turn it completely North and let it sit for about 10 seconds. Then spin it 360 degrees to North again and let it sit again for 10 seconds after the rotor box stops whirring.

Go outside and look at the antenna, it should be pointing North again.



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KB3LXY
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« Reply #4 on: March 20, 2006, 09:42:02 AM »

I use one to turn my Hex beam...

It is the same unit that u have. Except I went with the diditial remote. It has a feature that will re calibrae it automaticly...or it can be done manual. The wind does tend to move it some. But I find mine does not turn a full 360 degrees as well. I lose due Norh. It will spin to about 10-15 degrees of nort in either rotation. I compensate for this buy mounting the beam at a true N maganetic. About 15 degrees off. It still is not exact, but the beam is not Real strong in front to back so it works for me.

Not a bad rotor...as far as light duty goes. It does take winds in excess of 40-45 mph to vove it...you milage may vary
good luck
JohnB
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KA1MDA
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« Reply #5 on: March 20, 2006, 10:31:30 AM »

I think I have an old Radio Shack version of this unit- the control has a large knob on the top, and when you turn the knob an internal motor runs and causes the disk with the indicator dot to move till it lines up with the selected pointer position. If this is similar to your rotator, there is one other thing that may cause alignment problems.

I found one of the gears in the gear train between the motor and indicator disk in the control box was made of a very low-grade plastic, which after a number of years turned into the consistency of dried soap. In my unit, one of the teeth broke off, causing the indicator to skip and hang-up from time to time. Eventually, all the teeth finally broke off. I removed the gear in question, and the plastic was so deteriorated you could snap it in half with very little effort using just mild finger pressure!

Try doing the calibration listed in previous posts by rotating the antenna all the way one way, then all the way the other way. While doing the calibration, watch the dial with the position dot on it. If it does not rotate smoothly, or hangs up from time to time, chances are one or more of the gear teeth in the control box are bad.

My rotator turns a small TV antenna located in the attic, which obviously has no wind load to deal with. Luckily, my rotator is pretty consistent, and takes exactly 60 seconds to rotate 360 degrees. I ended up using it manually- rotate it to one stop (I can hear the sound of the motor change when the rotator motor stalls), and use the second hand on my watch to time the rotator. In fact, if you run the rotator to the stop counter clock wise, wait till the second hand gets to 12 o'clock, and start rotation- then the second hand becomes a pretty good compass indicator as to where the antenna is pointing!

Yeah, it's a pretty stupid way to turn the antenna, but it will do for now, as it will be replaced by the HD-73 currently on my tower sometime this year when I upgrade that unit.

Good luck, de Tom, KA1MDA
www.ka1mda.org
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