[TowerTalk] K8UR wire 4-SQR characteristics vs 1/4 vertical array design from N0AH

[Pete Smith]

At 02:34 PM 8/9/00 -0400, Steve Maki wrote:
>
>Pete Smith <n4zr@contesting.com> wrote:
>
>RE: half wave vertical dipole array
>
>>Modeling shows no need for radials, and good directivity extends all the
>>way from 3.5 to 3.85 mHz.  Advantages are simplicity and no dumped power at
>>all, though you do have to homebrew the switchbox.
>
>There is a section in ON4UN's book about the need for an extensive
>ground system with half-wave verticals, contrary to "popular myth".
>
>I assume he is talking of base-fed half waves, but wonder why center
>fed half waves would be immune from this requirement?

K3LR says that modeling at their QTH on 160 showed approximately 1 dB
increase in gain with the addition of elevated radials.  I haven't seen
that in some limited modeling efforts here.  I would think that half-wave
verticals still depend on a ground image for pattern formation, hence the
need for radials.  At least as I've implemented it, the W9LT/K3LR design
may rely mainly on the upper halves of the dipoles for radiation, with the
lower halves almost functioning counterpoise fashion.  Rather than coming
straight back to the tower base, the lower halves describe what is
essentially a quarter-circle, so that they arrive at the tower base almost
horizontal.  I can'r model that curve precisely, so I can't tell you what
is probably happening, but there it is ... and at least pattern-wise, it
does work.


73, Pete Smith N4ZR

The World Contest Station Database 
is back up and running at
http://www.qsl.net/n4zr 



--
FAQ on WWW:               http://www.contesting.com/FAQ/towertalk
Submissions:              towertalk@contesting.com
Administrative requests:  towertalk-REQUEST@contesting.com
Problems:                 owner-towertalk@contesting.com