Several requests were made asking what effect a vertical transmitting
antenna in the presence of a Pennant or a Flag would have.
I added a full-sized 160-meter vertical to my Pennant & Flag models and
tried a number of configurations. It became obvious that the only
logical way to erect a Pennant or Flag is to aim the antenna directly
away from the vertical. With A Pennant or a Flag aimed at the vertical,
severe degradation of the Pennant's or Flag's pattern occurs, even out to
a wavelength spacing. With the Pennant/Flag oriented perpendicular to
the vertical, much degradation also occurs with a large skewing of the
pattern off to the side in a direction away from the vertical.
_
The least effect is with the Pennant/Flag aimed directly away from the
vertical. Here are the results for this case with a Pennant (1st column
is distance to the vertical, 2nd column is the F/B ratio, 3rd column is
the 3 dB azimuth beamwidth - all measurements were taken at an elevation
angle of 31.3 degrees over "good" soil):
---- 38.83 143.2 (Pennant in the clear -- no vertical)
50' 9.39 188.4
100' 18.03 171.6
150' 28.13 155.0
200' 39.67 147.2
250' 43.03 149.4
Results with the Flag were almost identical. An interesting observation
here is that at 200' spacing and greater, the Pennant's F/B ratio
improves where it is slightly better than a Pennant in the clear. This
is apparently because the vertical is acting like a parasitic reflector,
as witnessed in models of the Pennant mounted perpendicular to the
vertical.
The moral of this story is that, if a large vertical transmitting antenna
is close by, erect the Pennant or Flag to receive in a direction directly
away from the vertical and space it as far as possible from the vertical.
73, de Earl, K6SE
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