ARLA/CLUSTER: Episódio 183 da série "Foundations of Amateur Radio": Como obtenho uma antena melhor?

[João Costa > CT1FBF]

Foundations of Amateur Radio #183

*How do I get a better antenna?*

The question that new amateurs most often ask after "What radio should I
buy?" is "How do I get the best antenna?".

In a household where you're the only antenna affected aficionado the
question is likely more along the lines of: "Why do you need another
antenna?".

The answer is pretty much the same, an antenna is fit for purpose,
generally only one purpose.

Going from A to B without walking might involve a car. If it's just you,
one seat is enough, if your local cricket team is coming too, you might
need more seats. If the road is rough, you might need a good suspension and
if it's the middle of summer in Australia, air-conditioning isn't a luxury
but a necessity.

Each of those different requirements varies depending on circumstance and
need. There are plenty more variables, fuel, distance, cost, and the deeper
you dig, the more choices.

Antennas are no different.

While cars have an element of fashion, colour, styling etc. antennas are
more utilitarian, radio amateurs rarely care about the colour of their
contraption, but they do care about cost, construction and performance.

Those three variables alone would make for plenty of choice, but we've not
yet talked about some other variables that come into play.

If you're a licensed amateur, picking the frequency you want to use is
obvious and a major factor in the choice of antenna, but if you're not an
amateur, that's not something obvious, but you have seen it before.

Without going into the physics of how and why, imagine all the antennas
you've seen in your life. There's a TV antenna on the roof, the antenna on
a transistor radio, an antenna on a car, the antenna on your Wi-Fi modem, a
mobile phone antenna, satellite dishes, you might have seen antennas near
train lines, on top of traffic lights, on a GPS and on a satellite phone.
You might not be familiar with all of them, but enough to know that there
is a huge range of different types of antennas. The more you look, the more
variation you find.

You might think that each of those different antennas was chosen at the
whim of the person spending the money, but actually, each of those antennas
was chosen for a specific job. Each of those antennas works on at least one
frequency, sometimes more and does so taking into account its purpose. Is
the antenna for sending, or receiving, or both? Is it supposed to work
regardless of where it's installed, or how high off the ground it is? Does
it need to take into account interference from a particular direction? Is
it meant for strong or weak signals, does it need to have a defined
lifespan, deal with a particular wind strength, etc. etc.

Answering each of those questions determines the choices made to select an
antenna from the infinite variety available.

As an amateur, my licence allows me to operate in six different frequency
ranges or bands. Technically that means at least six different antennas,
just so I can use the frequencies I'm licensed for.

Of course I'm only scratching the surface here, since I've already
explained that antennas come in many different shapes and sizes, each with
different characteristics and trade-offs.

So next time you wonder why so many different antennas, that's why.

If you've been wondering when I'll answer the bit about the best antenna,
you should already have a clue by now, but the real answer is
unsurprisingly: "That depends."

"On what?" you ask.

On which ever variables you care about and to which degree. The best
antenna depends on the questions you ask. Ask better questions, get a
better antenna.

I'm *Onno VK6FLAB*

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