Our current Satellite 3.0 Antennas have worked well in their portable configuration. We’ve had them to License Classes, Field Day, Ham Fests, and ultimately to Hudson Memorial School for the ISS Crew Contact there. As you can see from the photo above, the weight of the antennas causes the Fiberglass Cross Boom that we are using to sag and this is not a good situation for a permanent installation.
I decided to work with Spencer Webb, W2SW who owns AntennaSys, Inc. and M2 Antenna Systems to create a stronger Cross Boom solution. M2 Antenna Systems came up with a set of brackets, fiberglass truss tubes, and a Phillystran Truss System to support the ends of their Fiberglass Cross Boom.
The remaining problem to be solved was to reinforce the fiberglass tubes in the Cross Boom and Truss System to prevent the clamps which hold the antennas and other parts in place from crushing the fiberglass tubes. Spencer did an amazing job of making a new center section and polycarbonate reinforcing plugs to provide the needed reinforcements.
Polycarbonate material was used to avoid adding metal inside the Cross Booms and Truss Tubes near the antennas. Using metal for these parts runs the risk of distorting the antenna’s patterns and causing SWR problems. It was also necessary to keep Truss System parts like eye bolts, turnbuckles, and clamps away from the tips of the antennas for the same reason. As you can see from the photo above, Spencer did an amazing job making the needed parts!
The first step in rebuilding the Satellite Array was to install the new center section in our Alfa-Spid Az/El Rotator. I used a dial indicator to properly center the center section in the rotator. While this level of precision is probably not necessary, I had the tools available and it was easy to do.
The photo above shows one of the two completed Truss Supports. The trusses support the Cross Boom when it’s either pointing straight up or is flat at 0 degrees on the horizon. It’s important to adjust the horizon truss tube orientation to be slightly tilted to allow the antennas to operate in a “flipped over” configuration where the elevation points 180 instead of 0 degrees. This mode occurs in one of about every 5 to 10 satellite passes to avoid tracking problems with an otherwise south-facing dead spot in the azimuth rotator. Also, note the safety wire on the turnbuckles to keep them from turning after final adjustment.
You can see one of the polycarbonate reinforcing bushings at the end of the horizontal truss tube in the photo above. These are held in place with a small stainless steel set screw at the proper location in the fiberglass tubes. It’s also important to drill small drainage holes in all of the fiberglass pieces so that condensation and water seepage can drain out of the tubes. Without the drainage, water will accumulate, freeze, and break the tubes. I arranged these holes so that the tubes will drain when the antennas are parked in the vertical position.
With everything secured with a combination of tape and large cable ties, Matt of XX Towers rigged a suspension system and tram line to hoist the Satellite Array onto our tower. You can see how well-balanced the antenna system was prior to tramming.
The photo above shows the Satellite Array headed up the tram line. The tram line is anchored to a Gin Pole at the top of our tower and to a vehicle on the ground.
We removed the rotator and dropped the mast down into the tower to make it easier to get the satellite antennas in place on the top of the mast. Also, note the orientation of the Satellite Antennas – the elements are at 45 degrees to the Cross Boom. This arrangement helps to keep the metal in the ends of the Truss System from getting close to the antenna element tips.
Here’s a final photo of the Satellite Antennas with the mast pushed up and the lower rotator back in the tower. You can also see the rigging of the rotator loops for the Satellite Antennas and both the vertical and horizontal Cross Boom Truss supports in place.
The last step in this part of our project was to place the assembled M2 6M7JHV HD 6 Meter Yagi onto the mast. The 6M7JHV features 7 elements on a 36′ – 8″ boom. The antenna has about 13 dBi of gain and is optimized with a clean pattern to suppress noise from unwanted directions. The antenna was trammed up the tower with a light rope.
The picture above shows the completed antenna installation including a second rotator loop around the 6m antenna. The system has two azimuth rotators – one the turns just the Satellite Antennas at the top and a second that turns all of the antennas on the mast together. Our plan is to set the lower rotator to 0 degrees when operating with satellites and use the upper Alfa-Spid Rotator for Azimuth and Elevation positioning. The lower rotator will be used to turn the 6m yagi with the Satellite Antennas parked.
The next step of our project will be to install all of the control cables, satellite receive preamplifiers, and feed lines on the tower and test our new antenna system with the rest of our Satellite Station. You can read about other parts of our project via the links below.
- Portable Satellite Station Part 6 – Plans for a 4.0 Station
- Satellite Station 4.0 Part 1 – New Tower
- Satellite Station 4.0 Part 3 – Antenna Integration and Testing
- Satellite Station 4.0 Part 4 – Tower Camera and J Mode Desensitization Filter