Once again, you say what I am driving at better than I can.
I suspect most hams want an easy, quick solution they can wrap their
heads around. Impedance, reactance, inductance, capacitance, SWR,
return loss, and all that jazz is just too blamed complicated for most
hams, who often lack formal education in physics and electronic theory.
Having high SWR is a known problem and must be dealt with; high SWR
causes your rig to shut down. Other aspects are not show-stoppers, so
hams tend to ignore them. They don't know whether they have 99% or 39%
efficiency, but they are on the air and their radios don't shut down any
more, so they stop and operate.
So I suspect it was an easy fiction to accept - that low SWR means the
antenna is resonant. For being so wrong, there is very little
literature explaining why not.
I suspect most hams do not have the time to become experts on electronic
theory. It is not their fault, as there are hundreds of valid and silly
reasons, alike, for this. They do their best and figure, if they are
making contacts, then it must be a good antenna. A "good" antenna is
merely one that meets one's expectations. If one makes enough contacts
to suit him, he has a good antenna; what engineers and physicists might
say becomes irrelevant.
But SOME hams want more... they want REALLY good antennas, which are
"good" for good reasons, and that requires a substantial investment in
learning physics and electronics, and most hams cannot afford to do
that, or are unwilling to do what it takes, and focus only on what they
need to know to make it work. And I am not being critical of anyone in
this. It is like playing the guitar... most guys have a little time to
know a little about a little, and only a few guys ave a lot of time to
know a lot about a anything.
I passed college physics and learned a little about electricity 30 some
years ago. But I still cannot fully wrap my head around all the complex
measurements we need to know when designing an antenna system. I am
working on it, but I have not yet arrived. I still get confused when my
analyzer tells me there is 1.2:1 SWR, but only 18 ohms, and 178 ohms
capacitive reactance, or is that inductive reqactance?... So, sheesh...
I understand why some guys focus on SWR and decide that equates with
resonance - it works... their radios no longer shut down and they are
making contacts. Why bother with all that MATH ?
My local Elmer Guru guy told me the analyzer does not really tell me
impedance... and I am still trying to get what he means ... because I
know he is right and I wanna know. But until then, I guess I, too, must
read the analyzer and get on the air when the SWR is low enough. And I
will like it a lot better when I figure out what he is talking about!
----------------- K8JHR ---------------------
It IS a puzzlement.
------------------ K8JHR ----------------------
Robert Mcgraw wrote:
What ever happened to using the old fashion Millen Grid Dip Meter or the
Heathkit Tunner Dipper to find resonance? I can also use my MFJ 259
antenna bridge with a 2 turn loop on the input to find the resonant
frequency. These do exactly what is needed and thus find the resonant
frequency of a circuit or antenna. Then I use the MFJ or Autec bridge to
adjust the network for 50 ohms thus matching the Z of the resonant
antenna which is more likely not 50 ohms. From there regardless of
length, the 50 ohm feed line is happy as well as the transmitter or
amplifier feeding the feed line.
All too many times do we hear of hams trimming the antenna for lowest
SWR. That simply says they are adjusting the length away from resonance
to create some reactive component either +j or -j by increasing or
decreasing the length to make it look like 50 ohms. Even after doing so,
they do not have a resonant antenna but they do have a resonant load
which may or may not radiate well.
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