ARLA/CLUSTER: Episódio 202 da série "Foundations of Amateur Radio" - Antenas fora da vista e fora da mente ...

[João Costa > CT1FBF]

Foundations of Amateur Radio #202

*Antennas out of sight and out of mind ...*

Previously I've spoken about the dynamic nature of your station. Even if
from day to day use, nothing changes, things around you are always in flux.
Propagation changes, power fluctuates and the environment in which your
antenna operates is dynamic. Mobile stations even more so.

A few days ago we had a gale come through, strong enough to do some major
damage, rip off some roofs, break some trees, cause flooding, cause power
outages, plummeting temperatures, the first of the Winter Storms.

Obviously, checking out your antenna after such an event is expected.
Better still, stowing your gear before the event is even better.

Such extreme weather events are an obvious trigger to attending to antenna
health and well being, not to mention, maintenance and repair.

The thing is, it's not the only time you should check out your antenna.
Every day it's subject to change. The sun rises in the East, follows its
path along the sky and eventually sets in the West. The temperature and
humidity change throughout the day and continue to change through the night
and the next day it starts all over again.

Peppered with sun, rain, snow, salt, corrosion, expansion and contraction,
your faithful antenna sits there ready for you to get on air and make
noise, until one day it isn't.

You could just wait until it falls down, dies, perhaps becomes a hazard to
anyone within gravity range, not to mention, destroy your radio when you
key it up. Or you could check your antenna regularly and look after it.
Inspect and test it regularly, run you analyser across it every couple of
months, you know the drill.

Most antennas are out of sight for most of their life, but they should
never be out of mind.

During the weekly F-troop net we started discussing this - as well as an in
depth conversation about launching wire into trees - and there were several
suggestions worth investigating.

One amateur pointed out that the level of complexity in the air dictates
the amount of maintenance. A log periodic antenna on a rotator needs more
Tender Loving Care than a wire hanging off a tree.

Another suggested that you should regularly check the tower supports -
technically the mast supports - a tower is self-standing and a mast is not
- the best way to remember is that is the Eiffel Tower doesn't have any guy
wires.

Before a storm, if you have warning, you should check the supports, wind
down anything that goes up and down and you should think about how you're
going to earth the coax. I've previously covered the weirdness that
lightning and charge represents, even at distance, so don't wait until it's
overhead.

There were suggestions of using spark plugs and Mason Jars, but I've got no
supporting evidence either way. My geek background is sceptical, but I'm
open to learning more.

I've seen installations where a coax switch is used where the antenna is
switched to a shorted socket, so the inner and outer braid of the coax are
connected to each other.

One amateur suggested that an antenna tuner is cheaper than a radio, and
that if you leave it in place during a storm, blowing that up is cheaper
than blowing up a radio, but your mileage may vary. Also, if you have spare
cash to burn, I'm happy to take your donation and relieve you of that fire
hazard.

It's interesting in and of itself that antenna maintenance is often
discussed in terms of extremes, lighting, storm, wind, ice, etc. and less
so in terms of regular maintenance.

Finally, if you're only using a temporary antenna, you're not exempt from
this. You're actually likely to have more failure, since the act of
erecting and lowering of the antenna is likely to cause more wear and tear.

The antenna is the final part of the transmission chain and it should be
treated with the same respect as the power supply at the other end.

I'm *Onno VK6FLAB*
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