Shunt feeding of a broadcast tower by running a cable up the center is not a
new concept. KOBO in Yuba City CA did this in the early 90's. It is done
primarily to allow other services to mount antennas on the side of a tower,
thereby increasing rental income.
There was a paper written about this, and other antenna ideas, by Clarence
Beverage. It was published in the NAB 1995 Broadcast Engineering Conference
Proceedings.
I think the reason that this method is not widely used is that it is difficult
to find and adjust the proper tap point by running a cable up the center of the
tower. It is much easier to run one up the side and tap different points on the
tower until you find that major spot that gives you a 50 ohm match. My shunt
feed works so well that I have not wanted to mess with it and try the center
feed method.
If anyone wants a copy of the NAB paper, I can send you the PDF. However,
there is no specific technical info in the article to help you determine a
starting point for setting the proper tap point.
73 Dennis W0JXMilan, OH
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|