Topband: May 2005 EET article about the DLM
w8ji at contesting.com
Sat Aug 20 07:25:28 EDT 2005
The test antenna was a 7MHz monopole, 50% of the normal
quarter-wave size. Now one thing from an illustration that
begs more information was the ground system. It shows 150'
radials, which appear to terminate at the sea water's edge.
There is about a mile of seawater between the test antenna
and the calibrated receive antenna.
The article concludes; "Vincent's antenna designs were
tested using the official regime the Navy uses to certify
antennas. Vincent's Plano Spiral Top Hat antenna, at 7MHz,
was shown to have equal sensitivity to a normal quarter-wave
antenna but at 50% the quarter-wave unit's size. In
addition, bandwidth of the Vincent design was nearly twice
as wide as that of the quarter-wave unit.">>>
The initial Vincent claim read almost like CFA, CTHA,
Fractal, and E-H antenna claims. A very short antenna with
makeshift construction was claimed to produce better than
full size performance. The claims have evolved now to 50%
shortening over a nearly perfect ground produces equal FS.
The difference in FS between a conventional 1/4 wl tall
antenna and a 1/8th wl tall antenna is within measurement
error when the antenna is over a very good ground system and
when it uses a good loading inductor regardless of where
loading is placed. Brown, Lewis, and Epstein knew that in
As a matter of fact even with a loading coil Q as low as 250
(typically like air core #16 wire) and using base loading
there is less than 1dB difference between a 1/8th wave and
quarter wave antenna!
The apparent endorsement of the DLM antenna by the U of RI
does prove one thing....we need to work on our educational
system and stop the backslide in science. The U of RI and
Vincent are now at the level of early 20th century antenna
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