[BC] Directional FM Antennas

[Miltron]

Yes !
FM directionals are range tested and adjusted by the manufacturer and sighted and aligned at installation on the tower by a surveyor.
The manufacturer's range test is usually on only one bay and at full size or, often, at ~1/4 scale and ~4 X Frequency on a type of tower section or pole identical to its intended final mount.
Directionality is normally achieved with reflectors and orientation on the mounting structure. There is no phasing from one bay to another to achieve the horizontal directional pattern; a small phase difference between bays creates beam tilt. Larger interbay phasing  other than a full wavelength,, such as half wavelength, is used to control lobing of the vertical radiation.
After installation there is normally no field testing or monitoring of the pattern...........
M

-----Original Message-----
>From: Tom Dimeo <am at pa321.net>

>Are directional FM transmitting antennas phased in a similar 
>way as AM directional systems?  If so, is phase monitoring, 
>loop current monitoring, common point monitoring etc. required?
>
>If the directivity is accomplished using parasitic elements 
>as many amateur antennas do, are the directional 
>characteristics monitored in some way?
>
>Tom (just an amateur) does it show?
>