[BC] Directional FM Antennas

[Dave Hultsman]

In a message dated 2/18/2010 10:28:26 PM Central Standard Time, Radiofreetom at gmail.com writes:
>>  AM DA's monitor only the active driven towers...though
>> I know of some who have co-located towers on site and they monitor the
>> detune co-located tower's current as well.

 
Many early AM directionals used parasitic towers.  The engineers engineered the height and spacing of the tower and resonated the tower and in some case sapped power into a toaster oven type AM dummy load at the tower. Most of them had sample loops on the tower for monitoring.
 
The Radio Bonair on 800 in the Netherlands Antillies with 500 kW. origionally had 5 towers,  the center tower was fed but the other four were switched in and out and parasitically excited.  They had Non-D and two other patterens depending on what towers were switched into service.  I recall a paper presented at one of the first Carl Smith/NAB Directional schools in Cleveland that covered this system.  I believe now they only run 100 kW. Some one else may have much newer informationto share.
 
Dave Hultsman