[Antennas] SWR Isn't Enough

[A10382]

I ask these as questions, because at times, just when I think I 'got it',
along comes another view that appears to counter my understanding.  I think
they're the cumulative effects of education, logic, and legend & lore.  Not
a day goes by that I don't learn something....

I get the feeling there are some properties of basic physics that get
mangled by 'radio speak' terminology.  Sating the same thing in different
ways.
------------------

Isn't the thing we measure "VSWR" with really a watt(power?) meter ?  Is the
'measurement really power (Watts=E x I) in both directions through what is
effectively a rectifier ?

Are we really measuring 'voltage standing wave ratio' or is it being derived
from the relative (fwd/rev) power readings ?

At 1:1, isn't the voltage at any one point phased exactly opposite to the
current at that same point and same point in time throughout one cycle ?  At
anything higher, aren't the voltage and current slightly out of (time?)
phase and therefore some power is 'reflected' ?

We buy cable, fittings, antennas, amps, switches, and meters to match (or
reasonably match).  Where it doesn't match by design, we add matchers of all
types (baluns, tuners, feed coils, 'resonators', 'loading stuff', tuning
stubs, etc).  If after that, they don't exactly match (and they won't
exactly), some power is 'reflected' back to the rig or amp down from the
point(s) of mismatch?  Is this mismatch one cumulative wave or is it
individual reflections at different points in time from each effective point
of mismatch ?

Pragmatically don't we then fix the things we can (grossly bad mis-matches)
and try to 'tune out' as much of the remaining mismatch as practical
(practical is also subjective)?

Isn't 'Reasonable' SWR subject to interpretation?  The lower the better, but
isn't the desire to have 1:1 sometimes not worth the climb (figuratively and
literally)?

-----
One person is happy with 1.5:1 or so if they can reach and hear everyone he
or she  expects to for the freq, power, antenna, location, and current
propagation conditions to/from there (sometimes comparing this to other
similar setups).

Another person (not me!) puts on their belt and climbs to get the 1.31 down
to 1.26.

K............

<<---  END OF MESSAGE --->>
----- Original Message -----
From: "Rud Merriam" <k5rud@arrl.net>
To: "antennas" <antennas@mailman.qth.net>
Sent: Saturday, April 27, 2002 9:54 PM
Subject: [Antennas] SWR Isn't Enough


> So we know that SWR isn't enough in determining a 'good' antenna. What
other
> information is needed? Specifically, how do determine from a model if an
> antenna is efficient, i.e. putting the most signal into the air? Neglect
the
> radiation angles and directions. While they are important they are readily
> obvious from the model, it seems.