Elevation Rotor Adventure

My original plans for my 2-M EME station were to use things that I already had on-hand.  Well, that was a good "plan" but sometimes those plans don't always work out.  I had a TailTwister rotor which I had planned to use as an azimuth rotor.  However, the Hazer which I bought did not come with a rotor plate to accommodate a TailTwister.  It would have cost an additional $69.00 to purchase that mounting plate.  But before I purchased it, I became aware that the tailtwister was not a good rotor for EME use because of its braking system.  When the rotor stops rotating, the wedge brake seats into one of 60 segments spaced 6° apart.  That severely limits the pointing accuracy of the rotor.  Depending on exactly when the brake is engaged, I could be as much as 9° off the exact angle I needed to be pointed directly at the moon.  Since I was only planning a 2 antenna system, I did not feel I could give up that accuracy.  I need everything in my system to work as well as it possibly can.  So, I scrapped the idea of using the Hy-Gain TailTwister (T2X) and bought a new Yaesu G800-DXA for the azimuth rotor. 

Interconnects to EA4TX ARS-USB

Wiring Diagram for G-550

Still, from my prior days on EME and satellites, I had an abundance of elevation rotors.  I actually had THREE KenPro KR-500 elevation rotors so I felt I had that base covered.  But, Mr. Murphy reared his ugly head and the first two (and best of the three) elevation rotors failed to rotate on the bench!

Bummer!  But in looking at the facts, these rotors were 35-40 years old so it was not unreasonable that they failed to work.  And, considering their age, did I want to hinge the success of this project on that old a piece of equipment?

Still, I did not really want to put more money into this project than necessary.  In looking at all the usual websites, I found none used but I did discover that I could save $125 by buying only the motor and not the control box for a new Yaesu G-550 elevation rotor from R&L Electronics.  As they are located in Hamilton, OH, I had the new rotor the next day and it was quickly on the bench and ready to be tested with one of the control boxes I had from the KenPro rotors.

Of course, I then ran into a snag.  The KenPro motors had an 8-screw terminal block for connecting the wires to the motor and the new Yaesu had a nice 7-pin round connector.  That connector did NOT come with the motor I had purchased.  But, now Mr. Murphy threw me a bone in the fact that Yaesu uses the same connector on both the G800-DXA and the G-550 rotors and I had received just such a connector with the new G800-DXA.  It was surplus to my needs because I had purchased a Jetstream rotor cable which came with that connector already installed!

Modifications to Control Box

In looking at the schematics of the KenPro and Yaesu control boxes I noticed that the KenPro had a 70 uF capacitor wired across the motor windings but the Yaesu had a 100 uF capacitor actually inside the rotor motor housing.  I decided to simply lift the connections off one side of the 70 uF capacitor in my control box to remove it from the circuit since the new rotor motor already had the capacitor inside it.  At the same time, I drilled a hole in the rear of the control box, installed a grommet, and wired a cable that connected to the 29 VAC of the control box and the UP and DOWN connections to the rotor motor.  This will provide the interconnection to the EA4TX ARS-USB control box to allow it to control the elevation rotor.  You can see a photo of my modifications on the right.  Click on any photo to see a larger image. 

Once the rotor cable arrived from The Wireman it was time to connect everything up and see if the system worked.  Yesterday I wired the 7-pin connector (only 6-pins are used) to one end of the rotor cable and tinned the leads on the other end to screw onto the KenPro control box.  SUCCESS - It WORKS!  I now have a working Elevation Rotor and the control box is wired to connect to the EA4TX ARS-USB control system (once I clean the dust off it!)

This is a big step forward in the EME project because now I can mount the Elevaton Rotor on a short mast above the Azimuth Rotor and begin to install the antenna parts.  Just nine days ago I received my fiberglass/aluminum cross-boom, antenna boom supports, Rear Splitter mounting kit with 2.5m long rearward boom, and the cables to run between the antennas and the power divider.  Interestingly these parts were shipped from InnovAntennas in Great Britain just TWO days before!  The box was an 8-foot 4-inch long by 6-1/2-inch diameter round cardboard tube.  It was picked up in Hockley, Great Britain by FedEx on April 18th and delivered to my door at 1:24 p.m. on April 20th!  UNBELIEVABLE!  I simply could not believe the speed of that shipment!

So, with the Elevation Rotor piece of the EME project puzzle now working, the project can move forward - hopefully with some speed now!