Eric,

Here is another approach to the problem.

1. You need a rotor base plate that can be mounted at any level in the tower. Basically, it should rest on and be secured to the cross braces between the tower legs. 2. Next use a thrust bearing at the top of the tower. 3. Your mast needs to be heavy enough to withstand whatever winds you may encounter from storms when extended several feet beyond the top of the tower. At least half of the mast will remain in the tower. 4. The mast can be positioned vertically within the tower using a pulley at the top of the tower and a rope secured to the mast near the base. Helpers on the ground use the rope to raise and lower the mast while a person on the tower guides and secures the mast at the desired height using the thrust bearing. 5. You then attach the elevation rotor with its cross boom and antennas in as many steps as required to do so. 6. Using the rope to control the mast height, loosen the thrust bearing screws and raise the entire structure so that the satellite antennas have the necessary clearance above the HF beam. 7. Secure the thrust bearing screws and attach the HF beam. 8. Again raise the mast so that he HF antenna is at the desired height plus about 1 foot and secure it in place. 9. Attach the rotor base and rotor to the tower just below the base of the mast. 10. Lower the mast to the top of the rotor and secure it in place.

That is how I set up my current HF installation. Rather than having a satellite setup on top, I have an Cushcraft R-7 vertical which extends another 22 feet above the top of the mast and is spaced about 5 feet above my triband beam. You can put anything up there you want. I was not thinking satellites when I set this up many years ago, so my satellite antennas are on a roof mount.

I prefer center mounted antennas because I can mechanically balance the entire antenna system. I have balanced it front to back, side to side, and up and down. Basically I mount my antennas on a fiberglass cross boom and adjust the antenna positions (with coax attached) so that the whole setup is balanced front to back. Then I use another pipe and clamps to determine the rotor position so that the setup is balanced from side to side. Finally, I mount the heaviest antenna on the bottom side of the crossboom and the remaining antennas on the top side to further eliminate imbalance as the antennas rotate vertically. The idea is to minimize the stress on the rotor gears and bearings. Ideally, the rotor is not lifting or supporting any extra weight when it moves the antennas. The antenna structure could be moved with one finger if the rotor was not holding it in place. With end mounted antennas, the rotor brake and gears must support and lift the entire weight of the antennas every time the antenna elevation changes.

I'll also send you a picture of my current satellite setup. This is NOT the ideal setup because the rotor is not mounted in a tower section and there is no lateral support above the rotor for the mast. But it does give you a look at a setup with center mounted antennas on a cross boom with an elevation rotor all mounted above a 6 meter beam. The satellite antennas do rotate a full 180 degrees of elevation and clear the 6 meter beam. The longest antenna is an old KLM 2 meter circular polarized antenna that is 12 feet in length. Note that with the cables attached, the balance points move somewhat toward the rear of the antennas. Also, note the preamps just below the azimuth rotor.

And DON'T FORGET the preamps.

John Kopala N7JK

----- Original Message ----- From: "Eric Christensen" eric@christensenplace.us To: "AMSAT-BB" amsat-bb@amsat.org Sent: Friday, September 21, 2007 7:03 PM Subject: [amsat-bb] Mounting antennas on a tower

I'm contemplating antennas and a tower at the new homestead and I have a question.

If I can figure out how to mount an elevation rotator at the top of a pole and have the azimuth rotator rotating said pole from the tower would I have any problems with putting a small HF tri-band beam on the pole, below the elevation rotator, and then mount all my satellite antennas to the elevation rotator's pole? Has anyone done a combination like this?

73s, Eric Christensen, W4OTN AMSAT Area Coordinator - Southeastern Virginia USA AMSAT Member 35360