Re: [HCDX] Dxers Unlimited´s weekend edition for 1 -2 March 2007

["Prof. Arnaldo Coro Antich" <coro@xxxxxxx>]

Radio Havana Cuba
Dxers Unlimited´s weekend edition for 1 – 2 March 2008
By Arnie Coro, radio amateur CO2KK

Hi amigos radio aficionados around the world and orbiting Planet Earth… 
welcome to the weekend edition of Dxers Unlimited, reaching you while 
the Sun is in a very quiet state, zero sunspots, a blank Sun once again, 
after a lonely solar cycle 23 sunspot vanished behind at the edge of the 
solar disk... By the way, this sunspot group , number 983, forms part of 
cycle 23, something that can be affirmed because of its very near the 
solar Equator position. So once again we are entering into another 
period of very, very low solar activity that belongs to the tail end of 
cycle 23… Item two: for those of you located at latitudes above 40 
degrees North, there are chances of geomagnetic disturbances caused by a 
high speed solar wind, and it those disturbances do happen, AM medium 
wave broadcast band Dxing enthusiasts will once again be able to pick 
some really nice DX stations located South of your location…
Item three: Ionospheric oblique incidence sounders of the type known as 
chirp sounders, have confirmed that during the extended periods of very 
low solar activity, the nighttime maximum useable frequency has gone 
down to around 5 megahertz, yes, you heard it right, 5 megahertz for 
several hours, something that only happens during extremely low solar 
activity …
Item four: QSL on the air, QSL on the air to Dxers Unlimited´s listeners 
that have sent e mail messages to arnie at rhc dot cu asking when we are 
going to see better propagation conditions for the high frequency short 
wave bands… AND THE ANSWER IS : probably , not before the end of 2008, 
and if you discuss this topic with some solar experts, they will tell 
you that the end of cycle 23 is extending much further than any of the 
many forecasts made during the past two years… So, as the 2008 Northern 
Hemisphere spring equinox approaches, we will definitely still be 
experiencing very low solar activity and poor HF propagation conditions…
Stay tuned for more radio hobby related information, coming from Havana, 
I am Arnie Coro, radio amateur CO2KK, back with you in a few seconds 
amigos!!!
……


You are listening to Radio Havana Cuba, the name of the show is Dxers 
Unlimited, and here is item five of today’s program… more information 
about homebrew radios and tips about building them. For the past five or 
six years, I have been involved in the development of amateur radio 
transceivers, that is a ham radio station that is self contained in a 
single package, with some circuits that are shared between the receive 
and transmit functions. That’s a nice way of saving some components, and 
these radios are different from transmitter – receiver sets, that have 
completely self contained receivers and transmitters in the same box. 
Transceivers are of course more compact and they offer the advantage of 
single knob tuning. If your set is a transmitter – receiver, you will 
have to deal with two tuning knobs, separate tuning for the 
transmitter’s frequency and the receiver’s frequency… Well, the latest 
version of my low cost, simple transceiver, is now well under way, with 
many nice features that include a separate power supply. This new 
version of the Super Islander single band amateur transceiver is capable 
of running up to 50 Watts power input to the final amplifier stage, 
something that I have found to be necessary during this extended period 
of very low solar activity and poor propagation conditions.



The Super Islander MARK THREE follows the modular construction technique 
that has proven to be so successful in past projects, as one can test 
the modules as they are built, and if you want to upgrade a module, it 
is a very easy task to replace an old one and install the new upgraded 
module. The Super Islander Mark Three is a very flexible design, 
something that was necessary so that those who homebrew them may make 
the best possible use of whatever electronic components they have at 
hand. As a matter of fact, the Super Islander Mark Three can best be 
described as the ultimate in modular construction flexibility, with the 
design making possible for builders to change modules very easily and 
test upgrades, while , in case something goes wrong, one can just go 
back to the previous configuration of the transceiver. Maybe in the not 
too distant future, a complete kit o the Super Islander Mark Three may 
be made available by the Cuban Electronic Industry, which is now 
producing high technology medical diagnostic equipment that is used not 
only by the Cuban Public Health System, but that is also sold to many 
countries around the world. The Cuban Electronic Industry has the know 
how and equipment to produce high quality printed circuits, of the type 
required for amateur radio equipment, so a transceiver kit produced here 
in Cuba could be made available at much lower cost than a commercially 
assembled one… In the meantime, we continue to test our designs, and I 
can tell you that the results achieved so far with the receiver section 
of the Super Islander Mark Three design are very encouraging.

Now here is item six: Our number one most popular section of the program 
YOU have questions and Arnie answers them… I do receive lots of radio 
hobby related questions every week that are sent to arnie at rhc. Dot cu 
, or reach me via air mail postcards and letters sent to Arnie Coro, 
Radio Havana Cuba, Havana, Cuba…Many are answered immediately from a 
computer data base, while others require individual answers because of 
their nature, like the one that came in on Wednesday of this week asking 
about how one could tell if a transistor could be used as a radio 
frequency amplifier at some specific band of frequencies. Well amigo 
Oliver from Liverpool, England, as a very good friend of mine says, when 
trying to find if a particular solid state device would work, or won’t 
work as an amplifier at a specific band of frequencies you have to deal 
with two options: one try to obtain the original manufacturers 
information data, and if possible even their original test circuits, and 
if that is not possible, then just go the long way around and assemble a 
test jig, that will allow you to actually test the operation of the 
device under conditions that are as identical as possible as how it will 
operate when used by your design. Having access, for example, to a 
sophisticated instrument known as a transistor curve tracer will 
simplify your work, but there are some nice little tricks of the trade 
that can be put to very good use… For example, I have a test jig that 
uses a quarts crystal overtone oscillator circuit that can operate with 
crystals of the third and fifth overtone types… A transistor that will 
oscillate with the one hundred and ten megahertz fifth overtone crystal 
will certainly be a good amplifier device on frequencies up to around 20 
megahertz or so… And my test jig has a very simple power output meter 
that serves as a very good indicator to show the actual gain of each 
transistor under test at the specific frequency… It is then very easy to 
choose the best devices for the most critical applications amigos !!! 
There are many homebrew test instruments that will help you a lot 
Oliver, like a grid dip meter, a simple signal generator, and of course, 
a high quality digital millimeter that is nowadays an essential test 
instrument that should be in every radio hobby enthusiast tool box!!!
…..
Amigos you are listening to the weekend edition of Dxers Unlimited, our 
twice weekly radio hobby program, here is now item seven… An antenna 
topic, that is today combined with Ask Arnie, as this second question to 
be answered here today has to do with antennas. Listener Jennifer from 
Arkansas , USA, tells me that she lives at a downtown location, where 
the radio noise level is high. Arnie, she says in her e-mail, I can 
easily tell the presence of several computers, which are turned off late 
at night, as the noise level drops everyday like clockwork around 
midnight… And Jennifer asks what type of antenna can be used to minimize 
the noise coming from the computers. Well amiga Jennifer my advice is 
for you to buy or homebrew a magnetic loop antenna, which according to 
all the tests that I have done here provides the best option as regards 
to canceling noise sources that come from a specific location. BUT, let 
me warn you that if the computers generating the harmful radio 
interference are located all around you, it is going to be very 
difficult to cancel the noise. In any case, if you keep using your 
radio’s telescopic whip, you will notice that the computer generated 
noise is high, if you switch to an outdoor balanced dipole fed via a 
balun and coaxial double shielded downlead, the noise will go down, 
especially if you place the dipole so as to minimize the signal from the 
noise source, but as I said earlier, a tunable magnetic loop that can be 
turned around will provide the best possible cancellation of radio 
frequency noise sources that originate in your immediate vicinity… 
Professionally built, remotely tuned magnetic loops capable of operating 
between 10 and 30 megahertz are available from several manufacturers, 
similar magnetic loops for the frequency range 3 to 10 megahertz are 
also available, but they are much more expensive and harder to find… 
Home brewing a simple receive only magnetic loop is something that the 
average radio hobby enthusiast can accomplish following the many 
construction projects available from several Internet websites…After 
some practice and experiments, I am sure amiga Jennifer that with a few 
hand tools and thee help of a more experienced short wave listener or 
radio amateur you can homebrew your magnetic loop and install it so that 
your reception will improve. I have already sent you several photos and 
drawings of magnetic loops, just to give you an idea about how they look 
and how easily the receive only versions can be assembled using readily 
available materials...

And now amigos, as always at the end of the program here is your 
friend’s Arnie Coro CO2KK HF propagation update and forecast… Its freely 
available for distribution , of course… Solar activity again at rock 
bottom levels, some surprising and not expected Sporadic E events have 
happened during the past week at a time that according to past records 
they are much less frequent, so keep a good watch on frequencies above 
20 megahertz for signs of short skip that indicate the presence of 
Sporadic E clouds. Solar flux hovering around 70 units, no sunspots in 
sight and the high speed solar wind hitting the Earth´s magnetosphere is 
now slowing up, so the geomagnetic disturbance indicator is now moving 
back to normal values. See you all at the midweek edition of Dxers 
Unlimited, on the air Tuesday and Wednesday UTC days, and don’t forget 
to send an e-mail with your reception report and any radio hobby 
questions that you may want to ask to me… send mail to arnie at rhc dot 
cu, or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba


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