John Popelish wrote:
Roy Lewallen wrote:

Just a few weeks ago, I designed what amounted to a two-radial ground
plane antenna as part of a consulting job. It was made from copper
tape on a Duroid dielectric material, a lot like the window antenna
John described. An omnidirectional pattern was a requirement, and I
was concerned that either the flatness of the tape or the presence of
the dielectric might have some impact on the circularity of the
pattern. So I had it tested at a local lab. It was the most circular
pattern they'd ever seen, having about 1 dB maximum difference between
any two directions.


Did this antenna include any provision to prevent current on the outside
of the feed line?

Which direction did the feed line exit the antenna?


I don't know about Roy's antenna, but this subject has come up before,
and at the time I made a two meter vertical ground plane with only two
radials. No matter how I oriented the antenna, radially, I got the same
signal strength on my field-strength meter. And yes, I took precautions
to make sure the feedline wasn't radiating. (Many ferrite beads at
strategic places on the feedline to the point that feedline radiation
was undetectable.) If you can bring yourself to think in terms of
current directions and far field superposition of waves, this
behavior shouldn't be that hard to understand.
73,
Tom Donaly, KA6RUH