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Re: [HCDX] Dxers Unlimited´s week end edition for 16-17 August 2008
Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited's weekend edition for 16-17 August 2008
By Arnie Coro
radio amateur CO2KK
Hi mis amigos radioaficionados around the world! This is the weekend
edition of your favorite radio hobby program, the one and only that
really attempts to cover every single aspect of this wonderful way to
enjoy your spare time : RADIO... and when I say RADIO, I mean every
single aspect of our hobby that involves in one way or the other
electromagnetic waves... from monitoring the mysterious sporadic E band
openings that extend well up into the VHF region of the radio spectrum
to the so called natural radio signals, the whistlers that are extra
long wave Planet Earth´s own natural radio "noise". We can also detect
planet Jupiter's powerful radio signals with a simple homebrew
radiotelescope, and yes that´s something that can be done with a very
easy to install and rather small antenna system and receiving equipment
so simple in fact, that picking up Jupiter's radio emissions is surely
my favorite radioastronomy demonstration when someone visits my shack at
anytime time that Jupiter is above the horizon... The radio signals from
Jupiter sound like waves reaching a sandy beach,and you can be sure that
the signals are coming from Jupiter by correlating the astronomical data
with your radio observations. When Jupiter is below the horizon the
signals are not heard, and you start to pick them up when the big planet
can be seen from your location
Si amigos, there are at least 84 different ways you can enjoy the radio
hobby, and ham radio contests are certainly one of the most challenging
of them all.. Now let's start with one of those very attractive ways of
enjoying the hobby, that is turning yourself into an amateur solar
observer: Following the solar cycle on a day to day or even hour by hour
schedule is, and I warn you all, certainly addictive... and it is also a
very rewarding experience, as you will learn a lot about the complex
solar-terrestrial relationships that have such a great influence not
only on short wave radio propagation, but also in many yet unknown
aspects to mankind... Solar cycle gurus will tell you that watching the
Sun's activity on a day by day basis is very interesting, and once you
master the basics, then you can start making your own propagation
analysis that will lead to a much more fruitful enjoyment of whatever
time you devote to operate your amateur radio station or your radio
listening post...
I have received many requests for HF propagation analysis and forecasts
from contest operators in Canada, that were planning to activate the
rarely on the air CQ Zone 2, also hams from Germany and the UK have
requested a special Arnie Coro contest propagation guide,that have also
been used by several of the most active and rare DX expeditions like one
the most succesful Clipperton Island events... The main reasons for such
requests for a special contest propagation update are, first of all
antenna related, and in second place they are looking for advice on the
bands that are more likely to produce the best results during different
times of the day...
By the way there are several Internet on line courses that will help you
to learn a lot about the solar cycle, and once you master one of them,
your capacity to produce accurate and effective HF propagation updates
and forecasts will increase significantly...
Item two: Closely linked to item one: Solar activity is at very low
levels at this moment, and the effective
sunspot number Saturday at 12 UTC was just 2 units, while the mid
latitude A index, the geomagnetic disturbance indicator for latitudes
below 40 degrees North or so, was at 2 units, so you should expect
rather nice propagation on the three tropical bands, 120, 90 and 60
meters plus the AM broadcast band...,but we may soon be under the
effects of a high speed solar wind coming from a coronal hole, that will
spoil HF propagation still more above 40 degrees North latitude. Due to
the very high summer thunderstorms activity, your reception of
frequencies from 100 kiloHertz to 6 megaHertz is going to be rather
noisy to say the least, and it is expected that the recently formed
tropical storm FAY, hovering between Haiti and Cuba at the time you are
listening to this program will also act as a big static crashes noise
generator because of the thunderstorms associated to the bad weather
system.
Item three: ASK ARNIE, la numero uno, the number one most reported
section of Dxers Unlimited will follow, after a short break for station
ID...
Stay tuned, I am Arnie Coro radio amateur CO2KK , your host in Havana
.......
Si amigos ! This is Dxers Unlimited's weekend edition and here is now,
as announced, ASK ARNIE, la numero uno, your favorite section of the
show, today's question came from several listeners in the USA... they
all ask my opinion about power amplifiers for amateur radio stations
that use MOSFET devices instead of vacuum tubes or bipolar transistors.
MOSFET , is the acronym for Metal Oxide Semiconductor Field Effect
Transistor, a technology that has developed at a fast pace during the
past five years. The power devices using MOSFET technology are now more
rugged and reliable, and what is also important for amateur radio
applications, they are becoming less expensive.
Vacuum tubes power amplifiers are still made, and the quality of high
power triodes and tetrodes made using the metal to ceramic bonding
technologies can best be described as impressive, with the number of
service hours achieved going past the ten thousand mark, so, for all
practical purposes, ham radio high power linear amplifiers operated
under normal conditions will not require replacing the high power tubes
for a long time.
But, the fact is that MOSFET amplifiers are gaining in popularity, among
other things because they operate at much lower voltages, and the cost
of the active devices is going down .
Homebrew amplifiers using MOSFET devices are more difficult to build for
the average radio amateur than the equivalent power vacuum tube designs,
and some of the parts required for the MOSFET amplifiers are not easy to
find, but for the experimentally inclined radio amateur, homebrewing a
medium or high power linear for the HF bands should prove to be a
challenge that can be met with success.
Among the advantages of the MOSFET amplifiers in the power range from 10
to 100 Watts are that they can be operated with drain voltages not
higher than 24 to 28 volts, that lend themselves to the use of modern up
to date technology switched mode power supplies that are very efficient
and lightweight too.
My answer to the listeners that requested information about the
selection of factory built high power amplifiers or new transceivers
using MOSFETs or bipolar transistors, is to go to the MOSFET based
designs, because they are typically much more rugged than the bipolar
transistors, as some of the most recent HF and low band VHF amateur
transceivers have clearly demonstrated.
inforhc@xxxxxxx, si amigos, inforhc@xxxxxxx is my e-mail address where
you can send your radio hobby related questions for the ASK ARNIE
section of the
program, your signal reports and QSL card requests, and also your ideas
and suggestions for improving this program... VIA AIR MAIL, send your
postcards
to Arnie Coro, Radio Havana Cuba, Havana, Cuba... now here is our next
item of today's show...
There are now many more radio amateurs in Cuba than ten years ago, our
hobby is growing here, and the new ham radio operators have quickly
learned how to operate during emergencies. At the moment I am writing
the script of this weekend edition of the program ,radio amateurs in the
five easternmost provinces of Cuba are getting their stations ready as
Tropical Storm FAY is approaching. According to Cuba´s top tropical
cyclones expert , ProfessorJose Maria Rubiera, the people living in the
eastern provinces should began preparations to deal with heavy rains and
tropical storm force winds as the newly formed FAY either makes landfall
or passes very near the southern coast of Cuba… Already tropical storm
FAY has poured a lot of rain over the Dominican Republic and Haiti, and
it is expected to gain more strength when it enters the very warm waters
of the Caribbean sea south of Cuba.
As always amateur radio operators provide voluntary emergency
communications alternatives , deploying portable stations at remote
locations where normal cable and fiber optic phone services may be
affected by the storm.
.....
Now, here is the technical topics section of Dxers Unlimited, now
ranking as the number three most popular according to listener's
correspondence, closely our HF and low band VHF propagation updates and
forecasts offered at the end of the program... Today I will tell you
about a very simple antenna system for the 2 meters band, that has
proven to be very effective during tropical storms and hurricane , as
well as other emergencies. It is made with a length of RG58U coaxial
cable, but you can make a more rugged version using RG213, or RG8X cables.
This antenna uses a single coaxial connector that is used to connect it
to the 2 meter band rig, be it a mobile , a base unit or a handie
talkie. The antenna itself is made by removing the outer insulation from
the coaxial cable for a certain length, then folding back the shield of
the cable over itself for a length of 51 centimeters, and leaving the
center conductor extending for a length of 49 centimeters. To complete
the antenna , you make a coaxial cable choke of 8 turns, that starts its
winding at the point where the folded back shield ends… If you have at
hand a VHF standing wave ratio meter, then you can make the top end of
the antenna a bit longer, and trim its length for minimum standing wave
radio at the center of the band… This antenna can be hanged from any
available support, and has shown a noticeable gain over a handie
talkie´s small antenna, the ones known by hams as rubber duck, because
they resemble the tail of a duck. This half wave coaxial dipole can be
rolled up for easy transportation, and the fact that it has only one
coaxial connector makes it much more reliable than other portable
antennas that require insulators at the feed point. My own practical
experience is that this antenna is more reliable than the classic J type
end fed halfwave dipole made from 300 ohms or 450 ohms transmission
line, that requires the coax to be soldered to the twin lead, something
that can be the source of trouble , as it has often happened… So follow
your amigo Arnie Coro´s advice and homebrew a 2 meters band coaxial
cable dipole and keep it ready to provide emergency communications with
your amateur radio station whenever needed… Remember that providing
emergency communications under the most difficult and challenging
circumstances is perhaps the main reason why valuable radio spectrum is
allocated worldwide to the amateur radio service !!!
And now that we are talking about emergencies, do remember to include in
your emergency communications kit , a line voltage spike protector for
your AC power supply, because emergency generators tend to produce very
damaging voltage spikes that can kill your equipment if it is not
properly protected, nowadays lot of electronic equipment include spike
suppresors at the power line input
One of the most interesting features of these spike or transient
suppressors is that they are designed to fail into a so called heroic
failure mode, shorting out the input so that the protecting fuse will
blow if the spike reaches the device's preset limit for a certain period
of time.
QSL on the air… QSL on the air to amigo Hector in Puerto Rico who sent a very nice e-mail message requesting more information about HF propagation forecasting computer software. I must say that the in my opinion the W6EL HF propagation forecasting program, that is freeware , is certainly the most user friendly, easier to understand and to use of them all…with the added advantage that it will cost you nothing !!! It can be downloaded from several Internet sites and the learning curve is quite fast !!!
So amigo Hector , you can start by downloading and learning how to use
the W6EL propagation program, and later on explore other more
sophisticated options that are also available.
And now amigos, as always at the end of the show when I am here in
Havana, here is our exclusive and not copyrighted, in the public domain,
HF propagation update and forecast, together with low band VHF
information too. We are still seeing sporadic E openings with some of
them reaching the FM broadcast band. Solar flux and sunspot count at
rock bottom levels, the flux at only 65 units and ZERO sunspots for
many, many consecutive days.The effective sunspot number is an amazingly
low TWO, and we are expecting an HF propagation disturbance to begin by
Sunday, when a high speed flow of protons from a coronal hole will be
reaching the Earth´s magnetosphere… See you all at the mid week edition
of the program next Tuesday and Wednesday UTC days, and don´t forget to
take a little time to tell me via e-mail what you liked most of this
show and any radio hobby related question you may want to ASK ARNIE…
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