On Dec 22, 9:13*am, Richard Fry wrote:
FOR DISCUSSION...

*YouTube video on this subject at
*http://www.youtube.com/watch?v=QWd0n...layer_embedded

The comments in italics were posted on another website, which prompted
my five points that follow. *Thought they might be of interest here.

It would be interesting to learn if the results and conclusions shown
in the
YouTube video have been confirmed from complete documentation by
an independent test lab.

but i have another idea that has come out.might be a game changer
check this out. i have been researching this and it could be the
breakthrough we need. a broad band antenna, no loading coil needed,
double the eirp!

Observations from watching the YouTube video...

1. A 1/4-wave monopole was used in the test. A 1/4-wave monopole is
self-resonant, so no loading coil was necessary. However it would be
necessary
for the electrically short monopoles permitted for unlicensed Part 15
AM, and
would still be needed if the FCC changed 15.219(b) to allow a 30'
"ground"
conductor.

2. A 1/4-wave monopole driven against a perfectly conducting ground
plane such
as shown in this video has a peak system gain of about 5.15 dBi. The
video
shows a resonant gain for that monopole system without the sleeve as
"1 dBi"
referenced to the gain of a log periodic antenna.

However by definition the term dBi means decibels with respect to an
isotropic
radiator, and a log periodic antenna definitely is not an isotropic
radiator.
The gain units used in the video are therefore unconventional, and
need further
definition.

3. The relative field radiated by a conventional 1/4-wave vertical
monopole
driven against a perfectly conducting ground plane always is maximum
in the
horizontal plane. Such a system radiates virtually 100% of the matched
power
applied to its input terminals.

Therefore the peak gain of that antenna system at resonance cannot be
improved
by putting a sleeve of any kind on the monopole.

The sleeve may change the shape of the radiation pattern of the system
without
the sleeve, though, which could change the field intensity at the
location of
the receiving antenna used in the test. This could account for the ~3
dB
improvement shown in their results when using the sleeve.

4. Nothing is shown in the video about the amount of matched power at
the
feedpoint with and without the sleeve. If that is not held constant
then the
test will be flawed.

5. The VSWR bandwidth of a monopole may be increased simply by using a
larger
cross-section conductor of "non-fractal" construction.

The whole video sounded like a lot of verbal sleight of hand to me.
Its a shame techs and engineers are not secure enough in their
knowledge to recongnize BS when they hear it and report it as such.
"The Emperor's New Antenna".

Jimmie

Jimmie