On 09/11/2012 08:56 AM, Richard Fry wrote:
"J.B. Wood" wrote...
the argument that the slant wire to the tower adversely modifies the
antenna pattern doesn't seem to hold up in theory or practice.

Linked below is a clip from "Radio Antenna Engineering" by Edmund
Laport, which does show some pattern effects from shunt feeding a
monopole. The FCC dislikes shunt fed radiators for AM broadcast
stations (especially for directional arrays), as their skywave radiation
patterns are inconsistent, and interference ratios are more difficult to
predict.

http://i62.photobucket.com/albums/h8...d_Patterns.gif

R. Fry

Hello, and that identical diagram appears in my 1961 copy of Jasik's
"Antenna Engineering Handbook" (McGraw-Hill Book Co.) in the chapter on
medium-frequency broadcast antennas. In narrating the diagram (Fig
20-9) Jasik states, "Figure 20-9 shows typical variations in vertical
pattern resulting from shunt feed. The radiated field from a shunt-fed
tower is essentially the same as that from a series-fed tower of the
same height."

The diagram only shows measured data for a slant-wire shunt fed tower
rather than a comparison of that with measured data from the same tower
being series-fed.

Apparently the FCC disagrees with Jasik. However I think the question
from my original post has been addressed ("Because the FCC requires
it"). Thanks, Richard. Sincerely and 73s from N4GGO,

--
J. B. Wood e-mail: