"Richard Clark" wrote in message
...
On Mon, 23 Aug 2004 03:01:53 GMT, "Jimmie"
wrote:

I was under the impression that radiation efficency was pretty much a"
no-brainer".If the antenna is built of quality materials with good
workmanship the antenna would be an efficent radiator with little ohmic
or
dielectric losses. The exception to this of course would be antennas that
use an earth ground. I just found I was losing at least 3 db to heating
up
the ground.

Hi Jimmie,

3dB heating up the ground with an antenna that has 5dBi gain in the
preferred direction and launch angle compared to an antenna that has
no ground and 0dBi gain in the same preferred direction and launch
angle may give you pause and allow the worms some comfort on a cold
day.

Workmanship and quality materials tests those reputations vastly more
for smaller antennas than standard sized ones. Those 1 meter loops
used for HF are not rated for the lower bands for very good reasons,
and they claim (and I believe them) high standards for their product.
However, if you could resonate them in the 160M band, you'd be lucky
to see 1% efficiency.

Small antennas carry a lot of baggage, and any claims of efficiency
superior to the standard antennas they replace are suspect. When they
qualify that efficiency in creative terms like "more efficient per
unit length" you would do well to skip that and ask for field
strengths out 10 miles. A model called the eh had an FCC style site
survey performed to which they crowed it proved their design was equal
or better to a full size antenna. The data revealed results 10 and 20
miles out were 15-17dB down below that same standard they were so much
more efficient than.

73's
Richard Clark, KB7QHC


Certain products that include antennas may have to be tested for emissions
on a standardized site called an OATS, but that is a very bad choice for
antenna measurements (distance is 10 meters at most, and there is a
perfectly conducting ground plane).

As an engineer, I prefer to see performance data obtained in as simple an
environment as possible. But as a ham, I also have to admit that most people
don't use antennas under "test range" conditions. I can easily imagine an
antenna that looks good in "test range" conditions, but is badly influenced
by real-life items like proximity to ground, chimneys and trees.

Does the FCC (or anyone else) define any standard site for measurement of
antennas? Could the closest thing be NIST's antenna calibration ranges?

Ed
wb6wsn