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TopBand: Flag & Pennant Modeling Report

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Subject: TopBand: Flag & Pennant Modeling Report
From: (Earl W Cunningham)
Date: Sun, 04 Oct 1998 23:59:01 EDT
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

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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