Yuri

I realize you are a smart and important guy who knows alot about
electronucs. But, when you enter in a thread at this time with statements
about defining "3 DB" I wonder if you think everyone else is supid except
you. Whats the point of defining "3DB??
I used to work with some very good engineers who happened to think
measuring measuring antenna heating was a fairly decent way of getting
"loss" data on an antenna. I happen to think it is a good way to get some
preliminary info on antenna loss.
So, when you tell me to "forget the igloo", you seem to have placed
yourself in a position where you think you know how to evaluate antenna
efficiency and that I dont. I dont think you are *that* smart.

Jerry


"Yuri Blanarovich" wrote in message
...

I sure disagree about being able to determine an antenna's efficiency
by
either resistance measurements or by measuring received signa;l strength
at
any one point in space.

From practical, engineer's point of view, and we are looking at shortened
(loaded) antennas, you (or at least I) want to know how efficient the
loaded
antenna is vs. equivalent (same pattern producing) antenna. You want to
compare
oranges with oranges. The ultimate indicator is how much is one better
(worst)
than the other producing more (less) transmit (or receive) signal. That is
the
ultimate parameter that we are looking for, that's what you want to
measure and
compare. We have dB as a unit for that. 3dB means you gain (lose) double
(power) signal. If you lose 50% in the heat, you will see corresponding
loss in
signal strength. So forget the igloo!


But, you are certainly a much smarter fuy than I
ever was. So, I am not equipped to get into a news group contest.

How did you arrive at that without putting me in the styrofoam igloo, or
that I
am Fuy? :-)

It is my contention that the antenna under test's complete radiation
pattern and field strength would have to be measured and integrated if
field strength is used to determine it's efficiency. That could get
coplicated.

NOT! That's why you want to use the same pattern producing antennas for
comparison (apples to apples) i.e. quarter wave (electrical) shortened
(loaded)
vertical vs. full size quarter wave vertical made of same material
(tubing).
You can make measurements at the same point (properly chosen) and compare
signal levels while swapping the antennas at the same test site.

It would have seemed to me that the loss in any "R" is dependent on the
current flowing in it. And, I'd be concerned that any resonances could
have
higher circulating currents at the operating frequency.


Circulating in what?

If you can point out the errors in my convictions, I'd like to read
about
where I'm wrong.


You can be "convicted" in anything you like. But you have to look at the
problems and see what are you trying to achieve. I always try to make
antenna
to produce the maximum signal in the desired direction, pattern. That's
what
you try to measure, evaluate. Anything else is just contributing factor
that
gets included in the final parameter - signal strength. You can fart with
heat,
resistances, etc., I do not use antennas for heating, I use them for
producing
or extracting signals and that's what I am interested in and want to
quantify.
You need proper "standard" and use proper parameters to compare your
"miracle"
against.

If Mr. Vincent "discovers" that his shortened antenna is more broadband
than
full size (same electrical length) radiator, than he has some serious
resistors
"broadening" the response. My dummy load is perfect broadband "antenna"
and
almost 100% "efficient" - turns almost 100% of power into a heat, but
radiates
almost nothing.

The point is, you can measure other things like heat generated by the
loses,
but you are neglecting other parameters that come to play, leading you
astray,
while neglecting the most important parameter - the result you are (or I
am)
after - the signal strength!
Does that "convict" you? Otherwise I rest my case.
Jerry


Yuri, K3BU.us