[BC] FM bays

[Richard Fry]

Glen Kipple wrote:
> Besides, the elevation angle of a 100-meter tower as seen
> from 15 miles away is miniscule.  What -- one degree?
> Two, if that?  I see no reason to expend a lot of RF a mile
> or two from the site when there is nobody there to listen.
________________

Below is a calculation of the depression angle, ERP at that angle, and the 
incident field intensity at the nearer of the two cities, for the conditions 
in the original post (view in a fixed font).  Earth curvature is included.

The calculation assumes that the elevation pattern of the antenna is exactly 
its calculated, theoretical value as typically provided by the antenna 
manufacturer.  In real life, it is not.

                    * ERP / FIELD STRENGTH vs. DISTANCE *

Antenna R/C  (HAAT, ft.): ? 328           (Radio horizon = 25.61 miles.)
Distance from Tower (miles): ? 13
Number of bays: ? 6
Bay Spacing, wavelengths (decimal): ? 0.75
Element function:
                     ERI Best Case (FMH/XH, FML/XL, FMWH)  = RETURN
                     ERI Worst Case (FMC, FMS, FMD)        = 1
                     Cosine^1  (CBR)                       = 2 ?
Max ERP in kW: ? 25
 -   -   -   -   -   -   -   -
  For 6 Bay Antenna at 328 ft. HAAT and 25 kW ERP max:

         Distance   Dep. Angle   ERP      dB from    50,50 Field
          (mi.)       (deg.)     (kW)     Max. ERP    mV/m  dBu
         --------    --------   ------    --------    ----- ----
           13         0.34      24.94      -0.01      4.0    72

RF