>Antenna Mast for beam out of tower Reply
by KD8BHQ on June 8, 2005 Mail this to a friend!
What size pipe is good for mast when using a beam? My tower will except 1.5" OD.<
::If your tower will only accept a maximum mast diameter of 1.5", that's a pretty light-duty tower. Most amateur tower thrust bearings or top sections will accept at least 2.00" O.D., and two inch diameter mast is the standard for HF beams. VHF beams, being lighter and smaller, are sometimes manufactured to accept 1.5" masts. Bear in mind that many rotors, especially the "CDE"/Hy-Gain type (CD-45, HAM-IV, etc.) are designed specifically for a mast diameter of 2-1/16", period. You can use a smaller diameter mast, but when you do, the mast rotates "out of round" (not concentric with the rotor), so it must be shimmed to make it look like it's 2-1/16", even if it's really smaller, to prevent problems.
>I would like to be 8' out of tower with the rotor inside the tower. I guess my question is what wall thickness is recomended for this install the beam is a 5 el. horz. 6 meter I plan on putting a 2 meter vertical stick above that. Or are my plans all wrong. Should the pipe be steel or aluminum.
::Again, with such small and light antennas, a 1.5" diameter mast should probably work. I'd use either high carbon steel with minimum .062" wall thickness or extruded (seamless) aluminum with .125" wall thickness. Either is a fine choice for this application. If you ever intend to install a larger HF beam on the same mast, it will need to be bigger, but it sounds like maybe the tower will need to be bigger, too.