I'm trying to figure out practical meaning of the vertical beamwidth on a sector antenna. I want to understand the vertical zone that is useable.
Lets say I'm putting a sector with no down tilt electric or otherwise, having a 4 deg vertical beamwidth on a tower. If I make a triangle where the acute angle is 4 deg, the long side (adjacent) is 5000 feet (about 1 mile distance from the antenna) and then that means tan4=x/5000 where x is the usable vertical distance (contained in the 4 degree vertical width) at 5000 foot distance? That makes about a 350 foot beam spread vertical at 5000 feet usable. So ... if the tower has the antenna 350 feet above AGL with no downtilt, then I can start using that sector well once I'm 5000 feet away? If I want the sector to be usable closer to that tower then I have to calculate the down tilt for the bottom edge of the vertical beam width to get the location within the usable X distance?
Is this the general idea how to calculate? I don't want to aim the centerline of the vertical beamwidth to be aimed right at my other node if it's at ground level, as half the rf will go into the ground ... right?
Just want the basic yes or no to the concept. Useable vertical beam width varies with distance from the sector ... so several miles away elevation changes beome less relevant. Correct? Not interested in obstructions and fine details of the frenel zone ... just basic is it possible or not possible.
Just want the basic yes or no to the concept. Useable vertical beam width varies with distance from the sector ... so several miles away elevation changes beome less relevant. Correct? Not interested in obstructions and fine details of the frenel zone ... just basic is it possible or not possible.
Ed
So yes, I believe your math is correct, but it's a trade off. You also don't really want half your RF wasted going above everything else. In real simple terms, if the vertical beamwidth is 4 degrees, it would not hurt to put in a degree or two of downtilt to reduce RF going over everybodies heads.
Ed
The documentation for Ubiquity Networks radios has, or at least used to have, azimuth and elevation plane patterns for both polarizations for their radios like the NanoStation and PowerBeam. One thing of which to be aware: their "bandwidth" is the -6dB width, not -3dB like you normally see. Three equally spaced 120-deg sector antennas will be -6dB at the overlap points.
Remember that the closer your target is to the tower, the path loss is less. Half the distance reduces path loss by 6 dB. And you need to have the target radio antenna looking up at the radiator on the tower. If it is fixed at the horizon, its pattern will be in the mix.
The pattern of a parabolic antenna off axis can be approximated by a parabolic expression: Gain (dB at angle TH) = Main Beam Gain (db) - 3db (TH/3dB BW)^2. You probably will need to build a spreadsheet to get your answers.