[BC] High Gain vs Low Gain Antennas

[PeterH]

On Feb 22, 2009, at 10:36 AM, WBRadiolists at aol.com wrote:

> Remember, I'm an AM guy. I'm still learning this newfangled FM  
> stuff! ;)
> 'tis a whole 'nuther world, indeed.

Putting in a 14-bay FM is a lot like putting in a 12-tower AM: the  
"aperture" (beam width) is reduced as the number of bays (tower- 
pairs, for AM) is increased.

On an FM, you may have to employ electrical and/or mechanical tilt to  
achieve the desired coverage with a large number of bays.

The analogy on the AM side is the aperture becomes so restricted that  
your Tx site (in the horizontal plane, as AMs are usually not placed  
on mountain tops) becomes much more restricted.

Take a look at 1190 in DFW: to cover Dallas (the COL) _and_ FW,  
nights, the Tx has to be on a 250 degree bearing, which line goes  
through the two metros.

This greatly restricts the possible sites to a few near Rockwall, TX.