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Re: [HCDX] Dxers Unlimited's weekend edition for 17-18 March 2007 ZERO SUNSPOTS FOR FIVE CONSECUTIVE DAYS !!!
Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited's weekend edition for 17-18 March 2007
By Arnie Coro
Hi amigos radioaficionados. I am Arnie Coro, radio amateur CO2KK, your
friend in Havana and host of this twice weekly radio hobby program...
Nice to have you joining me for about 17 minutes of air time, and here
is item one of today's show; , weather related tropospheric ducting does
enhance VHF,UHF and Microwaves propagation along the Gulf of Mexico ,
providing FM band Dxers in Cuba, Florida and South Eastern Mexico with
nice long distance reception for many hours. I expect that the high
pressure areas that generate such good tropo DX will be happening again
during the next several weeks.
Item two: A year ago a big sunspot active region, the one that grew up
to a size equivalent to ten times the size of the Earth was one of the
last really big one of cycle 23, now we must wait for cycle 24 to
provide us with really big sunspots..
Today, ZERO sunspots, and the same has happened during the past four days..
Item three: Dxers Unlimited's listeners email messages sent to
arnie@xxxxxx continue to include very interesting radio hobby related
questions, I'll be answering two of them a bit later ...
Item four: Spring equinox just around the corner, and its happening when
the effective sunspot number is at rock bottom figures: Saturday morning
local time in Havana, the effective sunpsot number was just 07 ....now
stay tuned or stay connected, depending on how you are receiving the
program, I'll be back in a few seconds after a short break:
.......
Si amigos, you are listening to 46 years old Radio Havana Cuba, and I
believe that we are now among the five oldest Latin America short wave
stations.... Yes, we can be heard also via satellite on the Hispasat I D
transponder 79, vertical polarization, in English from 05 to 07 UTC, and
I can assure you that the sound coming from that satellite feed sounds
exactly as if you were seating at the studio's control room !!! Now,
here is la numero uno , the most popular section of the program : ASK
ARNIE... with today's number one question sent by eleven listeners from
around the world .. including Australia, the USA, Canada, Barbados and
Nigeria... They all want to know , and this is a question that is quite
logical for the non-expert to ask, well they all want to know if plastic
insulated wire can be used to make antennas, or if the antennas MUST be
made using bare copper wire...ANSWER, and please listen carefully... YES
, you can use plastic insulated copper of aluminum wire for making HF
antennas...but if you are building a resonant antenna, one that is tuned
to a specific frequency, then the length of the antenna obtained from
the standard formula won't work, because antennas made of insulated wire
have to be trimmed to resonance in a painstaking process, as the
insulation does modify the way the wire works at the the high
frequencies bands... The second answer to this question, relates to the
use of a special black or dark blue color TEFLON insulated copper wire,
that is used by many short wave listeners and amateur radio operators to
install stealth antennas that are very hard to see , even in broad
daylight. YES, you can use TEFLON insulated wire, and for a non resonant
antenna like an inverted L there is nothing that you have to do, just
install the antenna and that's it, but if you want to make a half wave
resonant dipole cut to say the 40 meters band, then the standard
formulas used to calculate the half wave dipole length simply won't work
!!! You must start with enough additional wire on each leg of the
dipole, say for example add ten percent of what the formula's answer
shows, and then, very carefully, and using an antenna analyzer or a low
power transmitter and a standing wave ratio meter, you must start
cutting identical lengths of wire off from each leg, until the antenna
is resonant at the desired frequency... So amigos, there you are, bare
copper or aluminum wire resonant antennas do come pretty close to the
calculated by formula resonant frequency, but plastic, any type of
plastic insulated wire needs to be carefully trimmed in length in order
to achieve resonance at the center operating frequency. For example, if
you want to home brew a 40 meters band half wave dipole antenna, and
your operating interests are CW and digital modes, then you should
calculate the antenna to resonate at 7050 kilohertz, a frequency that
will provide you with the possibility of operating from 7000 to 7100
kilohertz with a very low standing wave ratio...
By the way, the standard formulas for calculating half wave dipole
wire antennas are the following, listen carefully... if you are already
a metric person,then use this one 143 divided by the frequency in
megahertz, again 143, divided by the frequency in megahertz... for
example to calculate a half wave dipole antenna for the 10.1 megahertz
amateur band, you divide 143 by 10.1, and that equals to 14.15 meters...
Now that is an initial figure, so what you must do, is to make an
antenna that is slightly longer than the result obtained from the
formula, and then trim the antenna to resonance step by step, using
either an antenna analyzer or a standing wave ratio meter and a low
power transmitter. To calculate the same antenna's length in feet, use
the following formula: 468, divided by the frequency in megahertz.. so
let's calculate the same antenna... Here we go 468 divided by 10.1 and
the result is 46.33 feet, or 46 feet and 4 inches... so each leg of the
dipole is going to be 23 feet and 2 inches long, although, again, you
will certainly want to start with more wire on each leg, and then trim
the antenna to resonance, because it is a lot easier to cut the wire
than to properly add more wire to the antenna....
In a moment, ASK ARNIE part two:
.........
Here is now ASK ARNIE part two: several listeners from the UK,
Germany, the Netherlands, Sweden and Finland want to know what's their
best option to pick up Radio Havana Cuba in Europe. Well amigos ,at
present we are not broadcasting to Europe from Havana. We are relying on
the streaming audio fed to the Internet... BUT, radio is radio, and in
radio things never happen exactly the same way , not even twice... so,
YES , sometimes you can pick up Radio Havana Cuba's English language
broadcasts in Europe from around 00 UTC to around 06 or even 07 UTC on
the following frequencies, 6000 kilohertz, 6060 kilohertz, and sometimes
the 11760 kilohertz frequency can be picked up between 2100 and 2200
hours UTC... ...
Item four: Here is now a tour to my radio and electronics workbench,
where , as usual, not one or two, but in this particular case three
projects are in progress... The high priority project , now almost
finished is a switched mode computer power supply adapted to provide
13.8 volts DC at 10 amperes to my 2 meters band FM transceiver. The
conversion of the computer 250 Watt power supply was a rather easy job,
and I must add that the first on the air test brought back excellent
reports. In my humble opinion, with the enormous number of computer
switched mode power supplies than gathering dust everywhere, building a
standard linear , transformer powered power supply to provide you with
voltages between 12 and 14 volts at currents up to 25 amperes , is
absurd... The computer supply is compact, self protecting from short
circuits or overcurrents and last but not least, will cost you
absolutely nothing 99 percent of the time !!!
My good friend Luis Rodriguez CO2LR , that's his ham radio call sign,
did a beautiful job converting an ex Pentium One machine computer power
supply to a unit that provides power to his both transceivers, the 2
meters FM 45 Watt output unit and his 100 Watt HF 9 bands rig...
Luis told me that he actually keeps both radios fed at the same time
from the same modified computer switched mode power supply, because he
never has to transmit with both rigs at the same time, and when he is
on HF, he can then keep monitoring the 2 meters band,and
Oh YES... CO2LR is a retired person for whom the radio amateur hobby
has become a very important part of his life.... Luis is always
monitoring the local Havana 145.190 repeater, as well as the wider
coverage 145.110 megahertz EL SALON repeater that provides coverage to
Havana, Pinar del Rio and the Isle of Youth from a mountaintop location
at the Sierra del Rosario man and the biosphere reserve.
Luis told me that power supplies from 486ss, Pentiums One , Two and
Three can be easily converted, but that the supplies used by the more
older XT's are more difficult to do the conversion on them. Thursday
morning I got an old 486 power supply from a friend, after my standard
supply for the 2 meter band FM rig failed... and that's why I have the
486 supply conversion in the high priority area of the workbench !!!
An antenna design for the new Havana UHF Station, Canal Habana is
also almost completed...It's a QUAGI, antenna, with a quad type
reflector and driven element, while the directors are made from number 8
copper wire , or welding rods.
......
While writing the script at around 5 o'clock in the morning local
time here in Havana, and YES I do like to wake up very early to enjoy
some AM broadcast band DX ... well while writing the script I took a
break and installed the four AA penlight cells on my three transistors
and one integrated audio amplifier circuit in order to try to catch some
AM broadcast band DX, and effort to proved to be worthwhile, as I was
able to pickup stations from Costa Rica, Colombia, and of course the
Eastern Cuba with excellent signals and a rather nice signal to noise
ratio,that is a consequence of the very low geomagnetic activity that
has prevailed for the past several hours... Radio Rebelde's transmitter
on 600 kilohertz from San German, Holguin Province, and Radio Victoria's
1050 kilohertz transmitter from Las Tunas province where coming in like
local stations here in Havana at 5 o'clock in the morning , and I also
noticed an increase in static crashes when aiming my long ferrite rod
antenna to the North, something that was obviously related to
thunderstorm activity at more than 700 miles away from Havana.
And now amigos today at the end of the program there would not be an
Arnie Coro's Dxers Unlimited HF plus low band VHF propagation update and
forecast... because today I am not in Havana and this program was
recorded several days in advance of the day that it is going on the air.
My apologies amigos, but I am sure that you will understand that a
propagation update and forecast must be done just a few hours before it
actually goes on the air, something that is impossible today...Hope to
have you listening to upcoming edition ...and don't forget to take a
little time to send your email signal reports, comments about the
program and radio hobby related questions to arnie@xxxxxx or VIA AIR
MAIL, send a postcard or letter to Arnie Coro, Radio Havana Cuba,
Havana, Cuba.
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