Sunday 20 January 2019
Arnie Coro CO2KK
Hi amigos, welcome to the weekend edition of your favorite
listener oriented, technically minded radio hobby program, coming today once
again directly from right next to my ham radio station CO2KK, exactly
as it happened many years ago, on the 27th of October of 1998, when I was
sending an advance warning to radio amateurs in the Caribbean and Central
America as the huge Hurricane Mitch was approaching the area. As many of you
that heard that program remember well, a great number of radio amateurs in the
Caribbean participated in a large-scale communications effort related to one of
the most powerful storms ever seen in the area ever.
Amateurs in Canada, the United States of America, South
America and even from Europe helped by providing relays on the 40 meters band
when long skip made it impossible to work on that band, and as expected
practically all the 2 meters band repeaters in the affected areas were damaged
or totally destroyed by the hurricane force winds, landslides and the lack or
commercial power. The availability of the 80 and 40 meter band amateur
equipment that can operate using small generators or even car batteries has
proven to be a great asset when weather or earthquake emergencies destroy local
telecommunication facilities, or make using them almost impossible due to
excessive traffic generated during the emergency. The 40 meter bands long
distance relays of weather data for stations located in the affected areas and
the forecast centers is vitally important too.
Item Two: A detailed explanation of why emergency
communications provided by amateur radio operators are essential during hurricanes
and earthquakes, as well as large scale accidents. Hams using portable
equipment that can be powered from standby power sources are able to keep vital
links to the affected areas among the important information provided on those
two way links are weather data taken at places that were there, are no official
weather stations, advance warning from possible flooding and help during search
and rescue operations, and later after the storm is over, the amateur radio
links are used to help medical aid workers, to select landing sites for
helicopters and planes and in general to keep things moving during the very
complex post hurricane period.
Among the most interesting aspects of the way that hams
provide emergency communications is how simple antenna systems, low power radios
and good and very well-trained operators combine to keep communications flowing
Most of present-day amateur disaster area communications
is done using single sideband voice, but the increasing availability of
portable lower cost lap top and notebook and tablets computers are encouraging
the use of digital radio links, which are much more reliable, use less
power and are also less prone to interference. Computer to computer
communication via a radio link is an ideal way of handling emergency traffic,
but as a friend of mine likes to say it is a developed country approach, but
lower priced computers that are now available are making possible implementing
keyboard to keyboard emergency communication links by amateurs in less
developed parts of the world.
More about emergency communications during natural
disasters a little later in today's edition of Dxers Unlimited, coming to you
directly from my home location, right next to CO2KK my amateur radio station that is
now part of not one or two, but actually three emergency communications
networks on the 20, 40 and 2 meter bands Now let's take a break I'll be
back in a few seconds Short musical intercut
You may nowadays download from many public free access
Internet sites a large number of very interesting files dealing with antennas,
shortwave propagation, solar activity etc, that will help you to optimize your
amateur radio station and make it much more useful for handling emergency
communications whenever required.
You can also request our QSL card, by just sending an
e-mail directly to me send mail to inforhc@enet.cu
Item Three: Each edition of the big worldwide ham radio
contests like the CQ World Wide SSB or the WPX prefix contest help quite a
few newcomers to the amateur radio hobby to increase their total number of
countries, or DX entities as they are now called... worked. Many Cuban
radio amateurs both old and new participate in those challenging and
interesting events and some of them have achieved very good results too.
Item Four:Transatlantic medium wave AM band DX season is
now in full swing, something that happens has another peak time spanning from
December to the end of March, because of the expected decrease in ionospheric
absorption caused by the lower solar activity. Those AM band Dxes with
good receivers, and the special antennas required are able to pull several of
the most powerful stations from Europe and the Middle East quite easily during
solar minimum years , by using narrow filters that let those stations come in
between the 10 kilohertz channel spacing used by AM broadcasters in the
America's.
Among the easy ones from the other side of the Atlantic,
are several super power stations operating at the high end of the band, from
about 1400 to 1620 kilohertz. Don't be surprised if at around your local
midnight, when the sun is just rising in Europe, at least two or three of those
megawatt stations make themselves heard via powerful heterodynes or whistles
between the AM stations on this side of the Atlantic.
The super simple 2 element 2 meter band Yagi beam antenna
which is ideal for emergency work it is built using either standard TV
antenna elements, or heavy gauge copper wire The support for the antenna is
made from one of my favorite antenna building materials-you guessed right
amigos broomsticks.
This is a very compact antenna that will provide about four
or maybe a little more dB gain over a standard half wave dipole, but of course,
many more db's above the typical rubber duck antenna used by hand held radios
or handie- talkies The dimensions for this antenna are very easy to remember,
if you choose to do your homework in metric. The reflector element is 101 centimeters
long and the dipole driven element is 98 centimeters long The two are
separated by 50 centimeters of broomstick boom, and the antenna's driven
element is fed using standard 50 ohm coaxial cable I leave about 30 of 40 more
centimeters of broomstick behind the reflector element, so that I can tie the
antenna to any available supporting structure This is a portable emergency
antenna system, so it is made with low cost materials. The elements can be
taken from an old TV antenna, or you may buy aluminum tubing of about 10 millimeters or 1-centimeter diameter.
The dipole element is fed at the center, so the two sides
should be mounted on a piece of insulating material like acrylic plastic,
polyethylene or PVC, you should use good insulation if you want the antenna to
work well even when it is raining or snowing This is about the lowest cost
"amplifier" that you can think off. See by the numbers... a rubber
duck antenna used on a typical two-meter handie-talkie has a loss of no less than 6
db relative to a half wave dipole.
The Ultra-Low Cost 2 meter Broomstick Yagi antenna, has a
4 dB gain over a dipole in other words, if you replace the rubber duckie with
my two element makeshift antenna, your signal will be a whopping 10 db more
powerful, or 10 times louder than when you used the little rubber duck antenna
See you all at the middle of the week edition of Dxers
Unlimited next Tuesday and Wednesday UTC days... Send your signal reports to inforhc@enet.cu or via Air Mail to Arnie Coro,
Radio Havana Cuba, Havana, Cuba.