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Old 5-Jul-2013, 7:41 PM   #38
Pete Higgins
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Join Date: Apr 2013
Location: California, 58 miles @112 degrees from Mt. Wilson
Posts: 83
NTE ECG U-106 Rotor vs Radio Shack 15-1220


What are your impressions regarding the NTE rotator, compared to the Radio shack rotator?

No comparison. The Radio Shack 15-1220 is a 5-wire rotor that uses a balanced bridge for exact positioning. In the 50 years I’ve used it; it has never gone out of alignment. It also seems to produce more turning torque. The accompanying control box displays ‘N’ at the top & ‘S’ – ‘S’ at either end of rotation. Being an old flyer, that fits the way I think.

I also have an RCA 10W707S that is almost identical. Motor unit is exactly the same and control box looks identical except it displays ‘S’ at the top and ‘N’ – ‘N’ at either end of rotation. The one drawback is the directional calibration. Tic marks on both rotors are 4.5 deg. apart. When aiming towards a “True” heading, I can visualize the heading with respect to true north and align the knob pretty close. Degrees with respect to true south –not so much. (If I put the RCA in service, I’ll make stick-on labels for the cardinal headings (S-S, W, N, E) to cover the ones silkscreened on the control panel. Other than control panel screening & branding, they really are identical.)

The U-106 is a three wire rotor that uses a timing circuit for calibration. 3-wire rotors use AC synchronous motors that run at a predictable speed, and the control box simply runs the motor for the amount of time needed to turn the antenna from where the controller thinks it is to where the controller wants it to be. Over time, the position error grows.

After moving it to “home” or 00 deg., basically, you rotate it full clockwise (360 deg.), hit a button labeled “Initial” and it memorizes the time it takes to return to 00 or “home”. Unfortunately, it frequently requires recalibration. Since my signals come from four directions, it’s fairly easy to detect when it needs calibration because when I turn the array there is either nothing there or the signals are barely watchable. I probably have as much calibration mileage on the rotor as actual array turning mileage. Sometimes, when the calibration goes off, it won’t fully turn to a true 360 so to get it full clockwise you have to power off, power on with a “reset” turn some more and repeat the process until it visually has the array pointing north. I’ve since read that other folks are experiencing the same calibration issues with other brands of 3-wire rotors. I think AntennaCraft, Centronics, Channel Master, Magnavox, Philips, RCA, Stern and probably others sell this same design under their own labels.

I bought the U-106 because the literature said “Digital display indicates antenna position during operation” & “Pre-set to 12 TV/FM station directions for automatic antenna positioning”. What I didn’t pick up on was that the bearing readout was a 2-digit display. North is 00 or 36, east is 09, south is 18 and west is 27. My street is aligned with True North and my house sits squarely on the lot facing east so visually it’s easy to determine array alignment. Even after a fresh calibration, manually turning the rotor to display “18” can have me pointing somewhere between ~175 & ~185. Fortunately, if you “bump align” for max SNR and memorize the location to a pushbutton it seems to return to that location –at least until it goes out of calibration.

I’ve been tempted to put the RCA on the tower, but then I’d have the new U-106 just sitting in the garage gathering dust. It’s useable, but I couldn’t in good conscience sell it to anybody.

Hello Pete,
The TB-105 support bearing that you ordered is currently out of stock. The vendor will not have anything available until mid September.
Please let me know if you wish to keep your order open or cancel.
Thank You

Kept order open, so it looks like I don't have to go out in the 100 deg. heat (at least until September).

Found this ad in the Pitsburg Post-Gazette for Friday August 24th 1973. I think I bought mine about 10 years earlier for $29 or $39.
Attached Images
File Type: jpg RS 15-220.JPG (36.3 KB, 8972 views)

Last edited by Pete Higgins; 6-Jul-2013 at 8:10 PM. Reason: Update thrust bearing status + insert ad
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