2025 Rotator Project

Overview

The W9YT club station primarily operators a 20m/15m/10m beam, in addition to a 6m beam, all positioned by an M2 antenna systems OR2800 Orion motor, controlled via a RC2800-A box. Over time, the functionality of this system has decreased to a critical level, threatening the structural integrity of the beam, feedlines, and tower, necessitating repairs. The club has a reserve, older model 2800 and 2800 controller that it intends to restore and place into operations so that the newer model currently in use can be removed and repaired.

Primary project contact is Skylar NQ9Z.

Background

OR2800, with the believed point of failure called out in red.

Over the course of the last decade, progressively increasing play in the beam's directional holding ability has been observed by club members. Up to spring 2025, the beam could freely rotate as much as +/- 90 degrees of whatever setting was specified on the M2 Systems RC2800-A rotator controller (intended functionality is that the beam is statically held at whatever setting an operator specifies without any excess rotation at all). Additionally, operators noted a reduced range of rotation, with the beam generally slowing down - before stopping - at any settings above 250 degrees or below 50 degrees of rotation.

As of the time of writing (August 2025), damage sustained by antenna feedlines and other associated equipment suggests the beam may be able to fully rotate 360 degrees freely. The initial assessment of station engineers was that the internal gearing mechanisms (outlined in red) of the OR2800 Orion antenna rotator/positioned had sheared.

The initial antenna play and decreased lack of direction authority indicated that some of the gear teeth had rusted and subsequently mechanically failed, resulting in a gap in gear teething inside of the rotator.

Project Documentation

The legacy OR2800 rotator was opened and assessed. It was determined that the thrust bearing sealing the main box assembly from the upper mast unit had corroded and failed, leading to water intrusion. The thrust bearings were removed (INA Ball Thrustbearing: D9, 1” bore dia) and internal gearing wirebrushed and cleaned. The unit will be repacked with grease and assembled when new parts and materials arrived. Functionality was confirmed on the bench through rotating with a legacy RC2800 rotor.

The beam assembly mates to the rotator via a jaw clamp device. Two jaws sit atop the rotator (depicted in yellow above) in-between which a vertical mast with the beams mounted sits. To retain this mast on rotation, the jaws are torqued until tight. Consequently, we believed procedure for removing the rotator is to rather simply lift the beam/mast assembly that sits in the jaws up 3-4 inches to clear said jaws, at which point the rotator can be slid out from under the masts and replaced. This procedure is accomplished using a winch and gin pole - located in the corner of the shack - which can be attached to the main tower and serves as a pulley for mast lifting and hoisting operations.

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Notes from 23 November 2025

The following notes outline some ~2 months of tower work.

The beams are afixed to a central mast that comes down through the top of the tower approximately 2 feet before coming to rest on the rotator, which itself sits on a rotator shelf. A thrustbearing on the very top of the tower helps stabilize any pitching or translation that the central mast (pictured left). This bearing clamps to the mast via 4x 9/16" bolts that must be loosened prior to any lifting operations.

The 6x horizontal clamping bolts on the rotator are also 9/16", with nuts on the backside of the clamp that must be held with a wrench for tightening and loosening. The previously installed rotator mounts to the tower using 4x vertical 9/16" bolts, which differs from the legacy unit that is to be installed, which uses an identically spaced 7/16" bolt pattern. The clamps mount to the plate via 7/16" bolts that thread into integral threads on the mounting plate, rather than nuts as depicting in the image.

Repeated attempts at rigging the vertical mast with a winch and lifting failed because, as the 20/15/10 beam lifted up, the off-center pull of the gin pole caused the mast to tend to lean. The lack of any sort of locking mechanism securing the drive shaft of the rotator to the plate/jaw clamp assembly (other than gravity) meant that even with the clamps fully loosened, the tilting action of the mast would cause the clamps to be pulled up with the mast.

Eventually, the clamps would fully release from the rotator, allowing the mast to fully tip until the bottom end hit a horizontal crossmember of the tower, which posed and extremely challenging center problem. It was determined that this was sufficiently unsafe that it was unacceptable to leave for any duration of time, so attempts we made to hold the mast center with ratchet straps and DX Engineering Mast Lock systems, which failed due to the extremely high weight of the beam.

It was therefore decided on 23 November 2025 to lower the 20/15/10m beam to rest on top of the tower, before lifting the mast vertically through both the tower and beam.

All beam elements clamp to the tower via 1/2" nuts. On the 20/15/10 beam proper, six sets of clamping nuts on the upper side of the beam, and two on the lower side, had to be loosened before the beam could be lowered. Additionally, some nylon rope is affixed to either end of the main axis of the beam, which is clamped above the beam to help provide vertical support; this clamp also uses 2x 1/2" nuts.

The vertical support clamp was loosened to relieve tension, and the beam was rigged to the gin pole/winch. After all 8x 1/2" nuts were loosened, the beam was gradually lowered with some mechanical persuasion (the tower had to be shaken to overcome the friction between the beam and mast). With the beam fully lowered, the vertical support clamp was resecured (with slack in the lines) to provide a point to rig to the mast with the gin pole.

Following this, the mast was lifted clear of the rotator, which was removed. It was subsequently discovered that the legacy rotator we intended to install had both different sized mounting bolts, and a different sized mounting plate, which precluded our ability to reuse to mounting clamps pending construction of an adapter.

--NQ9Z

Notes from 11 April 2026

Tower was observed in relatively sound condition; the yagi had shifted at some point over the last several months, pinching the gin pole and pivoting it to be ~20 degrees off the centerline of the tower. The center mast had not downwardly displaced and was in the expected position.

Work began with WB9YZU, KE9CMP, NQ9Z, and W6LKK commencing layout of tools and equipment. KE9CMP and NQ9Z climbed the tower, carrying the restored rotator with mast clamps. Additional holes had been bored in the base plate of the rotator to accommodate new mast clamps. The rotator was maneuvered into the tower (mast clamps had to be removed) and bolted down. Mast clamps were reinstalled.

Work commenced on rerigging the gin pole in an appropriate orientation. Following this, an attempt was made to lift the 20m beam in order to relieve off-center stress on the mast. This required several attempts with altered rigging to finally accomplish the release of the mast. The mast was lowered into the mast clamps, connected, and full secured.

Finally, the beam and support wires were raised up by about 1" to allow free and easy rotation of the mast. Everything was affixed and the tower was observed to be holding position.

Installation of new feedline and control wires will commence at a later date.

--NQ9Z

OR2800 Failure Cause

It was determined following removal that one of the primary failure mechanisms of the new rotator that failed atop the tower was the shearing of a spline pattern on the central shaft that the beam mounting plate sits atop. The shaft, as designed, has a gearing pattern cut into it, which mates with a reciprocal female pattern on the flat mounting plate the clamps sit atop; we discovered these teeth to be completely worn off from within the plate on the removed unit.

Additionally, it was discovered that the vertical drive shaft that interfaces with the mounting plate was not integral to the large drive gear (see picture above). Rather, as designed, the drive shaft has a squared section that sits within a square cutout in the center of the drive gear. Through weather exposure and wind shear, the vertical shaft rattled and gradually rounded out the center cutout in the drive gear, causing an extreme amount of side-to-side plate in the shaft, further reducing antenna positioning ability.

Rebuild Order

1. Rotor
2. Shock Absorber
3. Mast Clamp

Shock Absorber

From VW Bug - forum posts cite a rubber shock absorber as assisting in dampening lateral loading. This is unnecessary for our application; tower already has a thrust bearing.

April/March 2026 - This was abandoned in favor of getting the donated Orion Rotor on the tower in 2026. Redrilled rotor plate for mast clamp brackets. (WB9YZU)

Measurements

Beam mast exterior diameter: 2 inches

Isolator to Rotor Plate: bolt distance - 2.25" (key side) 2.5" (outer side)

Rotator Pinout

There are eight sets of wire, but only four are used on either side.

The scheme is rotator:controller

• Blue:Brown
• Black:Red
• Red:Black

Notes from ITW

4th May 2018

A4 = BLU = Left Coil

A5 = GRN = Right Coil

A6 = WHT = (Common AC XFormer)

Right Coil DC Res, 5.2 Ohm (A6-A5)

Left Coil DC Res, 5.2 Ohm (A6-A4)

Both Coils DC Res, 9.3 Ohm (A4-A5) (Series)

Notes from WB9YZU

5/15/2026

In-Use | AC ORION control box (Labeled M2 OR2800 on outside) wiring:

T1 - AC Motor Ground (Red)

T2-AC Motor Winding CCW (White)

T3-AC Motor Winding CW (Black)

T4-Unused

T5-POS - Pulse from positioner mounted on motor inside the rotor (Yellow)

T6-POS Ground (Controller chassis ground) (Orange)

See also

2019 Rotor Notes