James Barrett wrote in
:

This thread has taken on a life of its own since I posted my first
question. I really don't understand any of this. I thought that I
wanted
an antenna with zero reflected energy or as close to that as possible.
Now it sounds like that is not always the case. I need to learn all
about SWR and impedance in regards to Antennas, from start to finish.
Is
there an easy-to-read tutorial out there for a beginner like me? Maybe
Ham Radio for Dummies has something about SWR and antennas?

Hi James,

Little wonder.

You asked a few questions:

1. Hi, I am learning about antennas, and and wondering about how antenna
tuners work. I've read you can use anything as an antenna as long as you
have a tuner.

2. Well, If I put up a wire dipole, and then use a tuner, what is the
best length of wire to use?

3. If I use an 80 meter dipole with a tuner, is that better than using a
10 meter dipole with a tuner?

My offering is:

1. That is a very simple statement, and for instance does not address
efficiency or a host of other issues (eg EMR safety). It is a restatement
of the popular ham maxim that "anything works" or the "any antenna is
better than no antenna".

2. The elements of an antenna system have a complex interaction, and
system performance can only be understood when the entire system is
analysed as a system. That means you have to start at the element level
and gain an understanding of those and then how they interact in a
system. Another popular ham maxim is "bigger is always better", it is
easy to say, but is doesn't apply in practice and is usually stated to
mask a lack of fundamental understanding.

3. You are a bit more specific, but not specific enough to answer
definitively. A half wave dipole fed with a balun and a reasonable length
of appropriate coax is an antenna system that takes only moderate
knowledge to design, fabricate, install and set to work with a high level
of confidence that it is working reasonably efficiently. You may even
wish to use an ATU (which is essentially an impedance transforming
network) for small optimisation of the load impedance seen by the
transmitter.

Whilst the temptation to use the antenna system described at 3 on
multiple bands may be great, and it is done, the outcome is often very
poor. For example, such an antenna designed for 80m (system efficiency
should be greater than 80%) is likely to be well less than 10% efficient
on 40m.

Be ware of simple Rules Of Thumb, there are often a plethora of unstated
assumptions, which when considered make them ROT.

Owen