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WWGK 1540

johnbasalla said:
A QUESTION FOR MR. EDUARDO: Quote: "The tower on the roof used a counterpoise system for the AM and the FM had a 4-element Pylon antenna on top". What is/was a counterpoise system and how did it work? What is a 4 element Pylon antenna and was that better than other antenna's of the day? I know of the Alternative Rock group named Pylon, but not a Pylon antenna (ha, ha).
Click to expand...

John, here's my view-

In context of a vertically polarized monopole antenna, the counterpoise is a ground plane implemented with elevated, suspended horizontal wires extending outward radially from the base of the antenna. It is an alternative to wires buried in the ground in the same fashion.

AM broadcasting in the US is normally implemented with vertical antennas. Most common is the monopole antenna, which in this case is a vertical tower, pole or wire 1/4 wavelength long (at operating frequency), and a ground plane extending outward radially from the tower base a distance of 1/4 wavelength (at operating frequency). It is routinely done with other dimensions, recommended upper limit is 5/8 wavelength, lower limit is that which achieves minimum FCC required system efficiency.

At 1450 1/4 wavelength is a distance of about 169 feet. Thus, a proper 1/4 wave ground system occupies land or air space circle with diameter of about 340 feet. Proper would be an antenna that is working very close to the theoretical efficiency of the design configuration.

At 540 a 5/8 wavelength tower would be a mere 1,138 feet.

The Pylon antenna is essentially a cylinder of sheet metal, mounted in a vertical position, with a narrow slot running from top to bottom. This cylindrical structure itself is the radiator. This has been used in UHF TV, but at FM things get bigger because the wavelength is longer (generally).

There is more to it than this, but that is a general description.

If you are thinking many AM stations do not have proper ground systems, you would be correct. It is not illegal to do so, provided FCC rules are met. Radio stations use antennas that work in consideration of all factors. I think a pylon FM antenna is a major motion picture that will fail at the box office of all things considered. There are other ways to radiate an FM signal.

In terms of providing some degree of broadcast service to a community, a compromised antenna is better than no broadcast service. Don't get mad. A broadcaster may be doing the best they can do under their circumstances.
 
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AMs have faded in popularity imho because most of its programming appeals to an older and older audience...one much less desirable by the majority of advertisers.

Since the overwhelming amount of listening to AM or FM stations is in car...AM’s signals are less of an issue than you might think.

Listening to radio of either band “at home” or “away from home” (in buildings, stores, at work, etc.) is much, much less than even 20 years ago.
 
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