[BC] Directional FM Antennas

[Cowboy]

On Thursday 18 February 2010 08:58 pm, Tom Dimeo wrote:
>  Are directional FM transmitting antennas phased in a similar 
>  way as AM directional systems? 

 Yes !
 However, the phasing is done in the interbay lines, not 
 in a conventional "phasor" as such. The result is the same.

>  If so, is phase monitoring,  
>  loop current monitoring, common point monitoring etc. required?

 No.
 At the time the technology was developing, the tech did not exist
 to monitor 100 mHz with the same precision as MW, so rules were
 written to assume certain "certainties" within certain tolerances.

>  If the directivity is accomplished using parasitic elements 
>  as many amateur antennas do, are the directional 
>  characteristics monitored in some way?

 Very much so, and no for the same reason as above.

 It's merely a matter of scale. There is no reason whatever that
 MW technology would not work at VHF, and vice-versa, except
 the practicality of manufacturing components to scale.

-- 
Cowboy