[BC] Bay spacing

[Richard Fry]

>...Also, consider a reduced bay polynominal antenna as well which fattens 
>the main lobe, but keeps steep downward radiation well managed.

Below is a link to the elevation pattern of a 3-element, binomially-fed 
array, which to produce no sidelobe(s) needs the elements to be spaced at 
1/2-wave vertical intervals.  The special power division needed makes this 
type of antenna relatively expensive.

This approach is good to reduce radiation toward the building on which the 
antenna is installed, but it also reduces radiation toward nearby buildings 
where penetration is important.

In this case, the relative field from the antenna is >20 dB reduced from 
licensed ERP over a span of 80° centered directly under (and over) the 
antenna.  Adding more bays to it would increase the width of that span.

So this is case for special study by someone who has all the details of the 
installation site, the nearby environment, RFR concerns, budget etc etc.

http://i62.photobucket.com/albums/h85/rfry-100/3-Bay_Binomial_Array.jpg

RF