Dxers Unlimited
Dxers Unlimited weekend edition for March 13-14 2007
By Arnie Coro
Radio amateur CO2KK
Hi amigos radioaficionados around the world and in space! Welcome to the
midweek edition of Dxers Unlimited reaching you when solar activity is
still at really very low ebb… I am Arnie Coro, radio amateur CO2KK and
here is item one of today’s program, solar scientists continue to try to
solve the puzzle about cycle 23’s final months… some researchers believe
now that we may see a rather extended tail end of cycle 23, while others
insist it is almost over by now. Another school of thought continues to
underscore the very high probability that upcoming solar cycle 24 is
going to be another record breaker, even capable of matching super
cycle 19 that sent the average monthly sunspot count up to two hundred
and seven, the highest ever recorded .
For us radio hobby people, an upcoming super solar cycle 24, with a
very high average sunspot count will also mean many solar flares and
geomagnetic storms too !!!
Now, we must just wait and see what’s going to happen during the next
several months, when it would be possible to have a fairly good
knowledge of the early phase of cycle 24…
Item two: The most popular amateur radio band around the world continues
to be two meters, spanning in some parts of the world from 144 to 146
megaHertz, while in other areas amateurs are assigned two more
megahertz, so the band in those parts of the world goes from 144 to 148
megaHertz. Two meters is very popular because with very simple equipment
and low cost antenna systems, radio amateurs are able to communicate
locally and even at longer distances when propagation conditions are
good. But the two meters band is not only a good place for FM voice mode
communications. Amateur operators can make good use of existing
satellites, and also enjoy very sophisticated communications modes, like
sending signals of high power transmitters to the Moon, using it as a
passive reflector as part of an Earth – Moon – Earth or EME link.
I have made several two way amateur radio contacts using the Earth –Moon
- Earth or EME mode while running at CO2KK, my ham radio station not too
much power output and a pair of small size Yagi antennas.
But, fully equipped EME capable stations use huge antenna arrays, high
power transmitters of up to the maximum legal power authorized to
amateur operators and extremely low noise signal preamplifiers… EME is
one of the more than 80 ways that you can enjoy our wonderful hobby…
yours and mine: RADIO !!!
Amigos, Dxers Unlimited’s midweek edition will continue in just a few
seconds… I am Arnie Coro in Havana, stay tuned or connected to our server:
……..
Si amigos, you are listening to Radio Havana Cuba, the name of the show
is Dxers Unlimited, and as always its my pleasure to share with you this
on the air and on the web time devoted to this wonderful hobby “RADIO”
here is our next item, the most popular section of the show “ASK ARNIE
“answering listeners questions as fast as they come in via e-mail sent
to [EMAIL PROTECTED]
Today’s number one question: came from Canada, from Ontario, listener
Wilbert asks if he can adapt an FM band Yagi antenna that is sold at a
popular electronics retailer outlet near his home, so that the antenna
will work on the 2 meters amateur band… And amigo Wilbert, the answer is
YES… it can be done, and as a matter of fact, you will end up with a
very nice looking 2 meters band antenna, at a much lower cost than if
you try to homebrew one. The typical FM band 5 or 6 elements YAGI
antenna has a boom length that provides more than enough space for a 6
to 7 element 2 meter band Yagi, and the length of the elements allow you
to cut them to the segment of two meters where you want to operate.
After buying the commercial FM broadcast band YAGI, you must
proceed to carefully measure each element and write down the result of
the measurement.
You will find that as in any typical Yagi parasitic array, the elements
lengths go from the longest one, the reflector, that will be very near a
half wavelength at the operating frequency, to the shortest one , the
last director, that will be much shorter than a half wavelength.
The FM band Yagi will probably be cut for a frequency around 100
megaHertz, because that is roughly the center of the FM broadcast band
that spans from 88 to 108 megaHertz, and that means that the longest
element of your commercially built Yagi will be very near 1. 5 meters
long, that is almost 5 feet long.
The second step required for converting a commercial FM band Yagi for
the amateur 2 meters band is to decide to which segment of two meters
you want new antenna to be optimized. For example you may enjoy talking
to friends on repeaters located in the upper two megahertz of the 2
meters band, from 146 to 148 megaHertz, so you may want then to optimize
your YAGI for a center frequency of 147 megaHertz, which is not exactly
the optimum way of doing it, but that in actual practice works quite well.
The third step is to use any of the available freeware programs that
calculate YAGI VHF antennas, and run it with the 147 megaHertz center
frequency design target.
Those programs generate several outputs: they will give you the length
of each element; how the elements are spaced along the antenna’s support
boom and also you will be able to see the actual theoretical horizontal
and vertical radiation patterns.
Your fourth step requires the use of a measuring tape and a hacksaw, to
cut the elements to the required lengths, following the data provided by
the YAGI antenna calculating software.
Fifth step, requires using an electric drill to carefully locate and
drill the holes where the elements will be fixed to the boom, that will
not be the same ones used for fitting the elements to the original FM
Yagi antenna
The sixth and almost last step requires a decision on your part, it you
want to operate using horizontal or vertical polarization. Using
horizontal polarization as needed for operating on CW and single side
band modes at the lower edge of two meters needs no change to be done to
the boom, but if you want to use vertical polarization, as required for
FM voice and packet radio modes, then you must drill new holes so that
the antenna may be installed for vertical polarization, in other words
the support clamp will be at 90 degrees from the original position used
for receiving FM broadcast band horizontally polarized signals..
The last step is to adjust the antenna for minimum standing wave ratio,
and for doing this you will need a VHF standing wave ratio meter, and
the help of an experienced radio amateur that has adjusted Yagi antennas
before… Take good notes of what you do, write them down, so that in the
future you will be able to adjust other antennas all by yourself…
Amigo Wilbert, I am sure that you will be able to find at a local radio
club someone willing to help you with your antenna conversion project…
And don’t forget that a YAGI with 5, 6 or 7 elements is a highly
directional antenna that requires the use of an antenna rotor if you
want to have around the compass coverage!!!
…….
QSL , QSL , QSL on the air from Havana to the many Dxers Unlimited
listeners around the world that have written during the past several
weeks reporting good reception of our 6180 kiloHertz English language
program heard between 05 and 07 UTC. The antenna we are using on 6180
kiloHertz is our Central North America curtain array, it is technically
speaking according to ITU definitions an HR 4, 4 , 0.8 system, that
meaning that it has 4 sets of dipoles set in four rows and four columns
a configuration that provides close to 20 decibels of effective antenna
gain over a half wave dipole placed at the center of the array. If you
are picking up Radio Havana Cuba on 6180 kiloHertz in English from 00 to
05 UTC,you are listening to the same antenna and transmitter combination
too.
Item six: For more than fifty years I have been fascinated with my
father’s 14teenth birthday present… a regenerative radio receiver kit
that he was sure I was going to be able to assemble without any help, as
dad told my uncle Armando during the birthday party.. that little radio,
assembled breadboard fashion is still working after half a century have
passed, and it has also served as the prototype for many other clones
that I have helped to build all along these years. The latest version of
my BIRTHDAY Regenerative is a bit more sophisticated than the original
one, and works beautifully with the sets of plug in coils that its proud
owner my eleven year old grandson has built so far… As batteries are
hard to come by locally and very expensive, this version of Arnie’s
Birthday Regenerative uses a very safe 24 volts DC supply to power my
grandson Arnie Coro the Fourth wonderful new toy!!!!
If you want to learn more about my BIRTHDAY Regenerative receiver, just
drop me an e-mail to [EMAIL PROTECTED] or a postcard to Arnie Coro, Radio
Havana Cuba, Havana , Cuba asking me to send you the Birthday
Regenerative receiver information package…
And now, as always at the end of the show, here is Arnie Coro’s Dxers
Unlimited, HF plus low band VHF propagation update and forecast…Let’s
begin with the actual sunspot count on Monday was 11 . The effective
sunspot number Tuesday morning local time in Havana, around 14 hours UTC
was 10 , with the maximum useable frequency curve going as high as 35
megaHertz over parts of Africa, a good indication of the excellent
equinoctial propagation we are enjoying despite the very low solar
activity. The BAD news is that we are now seeing the effects of yet
another geomagnetic disturbance as the solar wind is bringing in a much
higher than usual proton count… Keep time available for DXing from about
an hour before your local sunset to three or four hours after sunset,
and enjoy a second propagation peak starting at around two hours before
sunrise, and extending no more than an hour after sunrise…
And don’t forget to send me your comments about this program, signal
reports QSL requests and radio hobby related questions to [EMAIL PROTECTED],
or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, and Havana, Cuba
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