OTA Rotors: Channel Master, Yaesu, Hy-Gain, AlfaSpid, Others - Page 67 - Canadian TV, Computing and Home Theatre Forums

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post #991 of 1003 (permalink) Old 2015-10-07, 08:47 PM
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mdawdy: A rotator can't support a 15' mast with antenna. Even HAM-oriented rotators don't recommend supporting more than 2.5-3' of mast plus antenna without a thrust bearing.

DMX 68' tower, HyGain HAM 5 rotator, Antennas Direct DB8e & C5, Channel Master 7777 preamp, Siemens surge protection
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post #992 of 1003 (permalink) Old 2015-10-07, 10:49 PM
 
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Thank you, that is what i thought. I asked because my friend has been known to be right the odd time I'll be doing a normal, intelligent-guy install up top near the antenna, like the instructions usually say.

The TVFool says 40' because i have a 1-1/2" OD x 20' aluminum mast attached to the chimney. I am replacing this setup with a rotor and a Antennas Direct DB4e ...

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post #993 of 1003 (permalink) Old 2016-11-17, 02:08 PM
 
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CM 9251 maximum mast length

I will be mounting a db8e (top antenna) and an Antennacraft y5 7-13 on the same mast controlled by a CM 9251 rotor. The CM user's manual states that 3 1/2 feet is the maximum length. Optimum spacing between the two antennas is 36 inches ( half the wavelength of channel 7), however this would make the mast 60 inches, 18 inches longer than the maximum recommended length

The two antennas weigh just over 16 lbs. There is no wind load published for either antenna but some have guessed that the db8e is about 3 sq ft and I would guess that the 5 ft long y5 7-13 has a minimal wind load.

Need some opinions: Are the combined wind loads of my two antennas small enough to exceed the CM recommended maximum mast length?
OR Is a 5 ft mast too much of a load?

My next option would be to reduce the length of the mast by 16 inches ( 1/4 wavelength of channel 7) which would be only two inches over the 42 inch maximum.
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post #994 of 1003 (permalink) Old 2016-11-17, 03:07 PM
 
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I would keep to the recommended mast length, or close. I would put the VHF on top, with the db8e below to reduce the stress of its windload on the rotor, unless you are trying for some very weak UHF signals.

holl_ands has modelled the effect of two antennas being separated by less than the rule-of-thumb distance, and he didn't find a significant impact on gain or polar response, only on F/B (or was it F/R?) ratio. Be aware that those rotors don't have a brake, so strong winds may rotate it. You calibration will then be off (even without wind, they should be recalibrated frequently if accurate pointing is important).
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post #995 of 1003 (permalink) Old 2016-11-17, 03:11 PM
 
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thanks for that DXer!
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post #996 of 1003 (permalink) Old 2016-11-17, 11:24 PM
 
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DXer,

You might also consider something like an NTE TB-105 Thrust Support Bearing to add additional structural integrity to long masts with your TV Antenna Rotator.

I have an NTE U-106 rotor (similar to the Channel Master) and turn a Y 10 7-13, two HDB8X’s and a Winegard 10 element FM antenna. This doesn’t solve the lack of a break and the occasional wind-load turning but mine has been up for several years and is capable of turning my array. The thrust bearing supports all the weight of the array/mast combination and relieves a lot of side loading torque from the rotor.
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post #997 of 1003 (permalink) Old 2016-11-18, 08:27 AM
 
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Pete, it's actually chinadog who is asking the question.

With regard to the NTE TB-105 thrust bearing, I went to order one of these earlier this year, only to find they are no longer available new. I searched and searched, and eventually got hold of a well-used one. It seems like the usual story - the availability of OTA equipment grows ever smaller.

It is not difficult, however, to make a thrust bearing with a sleeve of ABS, PVC or metal piping sized to fit over the mast, and grease applied between the mast and piping. I used that approach successfully for 14 years until I decided to 'upgrade'.

For several years, I had a 91XG on a small rotator comparable to the Channel Master (the Eagle-Aspen DiSEqC rotor), with the pipe thrust bearing. I replaced the 91XG with a 'monster' CM3671 antenna. The rotor failed after a few months - due, I assumed, to the increased wind loading. I upgraded to a Hy-Gain Ham-4 rotor with the NTE TB-105 thrust bearing, and all's well so far.

I also have other three-wire rotors, and bench testing shows how quickly they get out of synchronization. Merely starting and stopping them several times in a full rotation puts them out significantly. Either the DiSEqC control (of the now-unavailable Eagle-Aspen rotor) or the potentiometer feedback of the ham rotors is necessary for accurate and repeatable pointing. Otherwise, one is obliged to run the rotor to end-of-travel each time to re-calibrate it if accurate pointing is desired.
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post #998 of 1003 (permalink) Old 2016-11-18, 10:21 AM
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Yes, the TB-105 is hard to find. A suitable replacement might be the Yaesu GS-050
https://www.dxengineering.com/search...rder=Ascending

YAESU GS-050 Rotors

https://www.gigaparts.com/yaesu-gs-050.html



http://www.ad5x.com/images/Articles/TB105.pdf

Another discontinued bearing is the Channel Master 9523:


If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 2016-11-18 at 11:01 AM.
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post #999 of 1003 (permalink) Old 2016-11-18, 11:47 AM
 
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Hi rabbit73, long time!

Sorry guy’s, I didn’t know I was sending you on a wild goose chase?

I’ve had one TB-105 for years and ordered another one from Wiley’s Electronics in San Diego, CA when I was setting up my antennas. I just checked their site and they no longer list them.

I have one Alliance-HD-73 Rotor, 3 really old 5-Wire rotors and the NTE ECG U-106 3-Wire rotor. The only reason I use the NTE ECG U-106 is because I couldn’t in good conscience sell (or give) it to anybody else. Fortunately, I use separate antenna arrays to point @ San Diego & LA so once I position my array’s they remain stationary. Of course the 5-Wire San Diego array never moves and I only have to “correct” the LA array when we have high winds. I think it’s criminal that manufactures even sell this poorly engineered design –especially to home users.
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post #1000 of 1003 (permalink) Old 2016-11-18, 10:09 PM
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Quote:
Originally Posted by DXer View Post

For several years, I had a 91XG on a small rotator comparable to the Channel Master (the Eagle-Aspen DiSEqC rotor), with the pipe thrust bearing. I replaced the 91XG with a 'monster' CM3671 antenna. The rotor failed after a few months - due, I assumed, to the increased wind loading. I upgraded to a Hy-Gain Ham-4 rotor with the NTE TB-105 thrust bearing, and all's well so far.
Hi DXer, wouldn't happen to still have the broken eagle aspen kicking around and be willing to 'donate' to a guy for cost of shipping of course, to use for diseqc projects would ya?

DB4E/VHF Yagi rotor FM Bandstop ap-8700 preamp 4way split LG lcd.
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post #1001 of 1003 (permalink) Old 2016-11-18, 10:20 PM
 
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Quote:
Originally Posted by majortom View Post
Hi DXer, wouldn't happen to still have the broken eagle aspen kicking around and be willing to 'donate' to a guy for cost of shipping of course, to use for diseqc projects would ya?
Sorry, no. Although it had ceased turning the antenna, when I stripped it down and bench tested it, I could find nothing wrong. It failed in mid winter, and I didn't retrieve it from the roof until spring, so I concluded it must have just been frozen. It currently waits to live another day turning another array 😊

It was such a great rotor compared to others in that price range for its accutate positioning system that when it failed, I wanted to buy the same model to replace it. As you well know, I discovered they were no longer available. It is so frustrating that all the good OTA gear of yesteryear is progressively being replaced by inferior products.
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post #1002 of 1003 (permalink) Old 2016-11-19, 08:02 AM
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I hear ya, I really wish someone else would get the point and release something similar
to the marketplace.

DB4E/VHF Yagi rotor FM Bandstop ap-8700 preamp 4way split LG lcd.
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post #1003 of 1003 (permalink) Old 2017-02-14, 01:17 PM
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Digiwave AR500 rotator data and tweaks

I don’t post often but thought I would add some data to the forum, if its not already known. This may help with future troubleshooting and preventing problems before they occur.

I purchased a AR500 Digiwave rotator from Lowes.ca for $123. It arrived within 24 hours and I proceeded to look it over. My experience has led me to make sure Chinese made devices work before installing so I removed the bottom plate from the drive unit to look it over. Case serial #1000501

The first thing I noticed was that three of the four 3\8” cap screws that hold the motor unit mounting plate to the case were loose by several turns each, only one screw was tight. I removed these screws completely and removed the motor assembly plate for inspection. Pleasantly surprised to see that all gears were metal and lightly greased with a white grease.

I measured the voltage of the 2 AA that came with it for the remote control and found one was dead, indeed the bottom of the cell was corroded, the other cell read 1.56V (normal)


Things found and fixed:
1 – The metal arm that sets the drive backlash only used one screw though there was a second threaded location for another screw which I added.

2 – The motor wires, #30 gauge or so looked like they could break with vibration so secured them with silicon caulk so they cannot move.

3 – Used removable loctite (#242) on most screws and nuts and reassembled the unit.

4 – Greased the main bearing (under the large rubber ring) as there was no grease. This is a machined aluminum bearing surface that rides on a stainless steel shim.

On the bench I measured the operating voltage and current to the motor on all 3 wires. Connected to the controller.
All measurements are with a Fluke model 83 multimeter and are 60 Hz AC, both rotation directions are shown, 3 feet of #18 wire were used for the test:

AC Voltage
Terminals 1,3 20.1 V, 20.5 V
Terminals 2,3 25.2 V, 20.1 V
Terminals 1,2 35.3 V, 35.3 V

AC Current
Terminals 1 628 mA, 786 mA
Terminals 2 631 mA, 782 mA
Terminals 3 648 mA, 652 mA

Stalling the motor produced very little increase in these current value, perhaps 50mA or so

After running the unit on the bench for 4-5 minutes I read the temperature of the motor winding and found a max of 53 degrees C using an IR thermometer.

Hope this helps someone.
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Last edited by samson51; 2017-02-14 at 08:06 PM. Reason: clarity
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