Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited's weekend edition for 25-26 June 2005
By Arnie Coro
radio amateur CO2KK

Hi mis amigos radioaficionados around the world and in space !!! Welcome to
the weekend edition of your favorite listener oriented, and technically
minded radio hobby program... YES... you are listening to Dxers Unlimited,
the one and only short wave program devoted to each and every aspect of our
wonderful pastime... RADIO...
From enjoying the thrill of a two way ham radio contact half way around the
world using a very low power QRP transmitter, to having a lot of fun during
a 2 meters band fox hunt at one of your city's parks... from getting ready
for an amateur radio contest, to spending hours and hours carefully setting
up your TV Dxing antenna system... SI AMIGOS, YES MY FRIENDS...radio is
unique in the sense that there is always something to learn, to experiment
with, and to enjoy... I am Arnie Coro in Havana, my ham radio call sign is
CO2KK, and you can hear my amateur radio station often on the 30 and 20
meter bands CW segments using my new 2 Watt rig, connected to a wideband
antenna that is working very well indeed. Now here is item one of today's
Dxers Unlimited... As the summer solstice had already gone by, we are seeing
late evening band openings on the 30 and 20 meter amateur bands, and very
good reception of international shortwave broadcasts on the 31, 25 and 22
meter bands.
Item two: Many e-mail messages keep coming in to my arnie@rhc.cu account
every day, and it's really nice to see how Dxers Unlimited's listeners
worldwide continue to enjoy this program and bring in so many new ideas,
suggestions and questions for me to review. Among the most recent ideas was
to create at least one CD ROM disk with the best of Dxers Unlimited for the
past several years... and then make it available to those interested... Sure
 it's a good idea that will require a lot of work on my part, something I am
just starting to do during this weekend... Item three: Simple wire antennas
continue to fascinate many of you amigos, among them the ultra compact two
element QUAD antenna for the two meters amateur band, that can be built in a
few hours using standard PVC insulated wire used for household installations
and PVC plastic pipe. But be aware of an interesting phenomenon... if you
don't strip the wire of its plastic insulation, the dimensions of the
antenna will be different than those coming from the standard two elements
QUAD antenna formula... And there is a very nice and easy to use software
program to calculate a VHF QUAGI antenna, a neat combination of a two
element QUAD and several linear parasitic director elements...
By the way that program, which is freeware, is available by just sending me
an e-mail message requesting the QUAGI antenna design program... send your
request to arnie@rhc.cu, again arnie@rhc.cu, and I'll e-mail the software to
you as a virus free attachment... More radio hobby related items coming up
right here after a short break... I am your amigo Arnie Coro in Havana, and
as always it's really nice to share with you all about seventeen minutes of
airtime during the weekend edition of Dxers Unlimited.
.......
This is Radio Havana Cuba, the name of the show is Dxers Unlimited, we are
on the air twice weekly, at several different times of the day, and using
also several different short wave frequencies, as well as our streaming
audio from www.radiohc.cu, every day from 05 to 07 UTC at this moment...
Here is now item four of today's show:  A simple, rugged, easy to transport
solar photovoltaic panel, a lead acid gel cell accumulator and a simple
homebrewed voltage regulator will power up your low power amateur radio
station and your short wave receiver at anytime... The solar energy option
is excellent for your emergency communications kit, and you will be
pleasantly surprised how even in somewhat dark days, the silicon solar cells
can provide enough energy to charge up the battery for nighttime use. A five
or ten watt power solar panel is ideal for this application, and let me add
that many ham radio contests have now special entry categories that provide
bonus points for stations using solar or wind energy for powering  the
equipment  during the contest. Amateur radio contests participants learn a
lot about fast and efficient communications procedures and field
installations, something that is extremely useful when actual emergencies
come up to your community .
Item five: The number of amateur radio stations in some countries is
extremely small. This is seen especially in the African continent, where the
presence of DX expeditions of people visiting from developed nations is
often the only possible source of a two way contact with that DX entity. My
perception is that helping develop amateur radio in Africa will be extremely
useful for the people of that continent, and this is an effort that could be
very well linked to already ongoing project designed to provide Internet
access from remote locations using satellite technology.  Item six: Tropical
Band DX season is now over in our northern hemisphere... high noise levels,
typical of the summer make Dxing on the 120, 90 and 60 meters Tropical
Broadcast Bands extremely difficult. Nevertheless, very early morning
monitoring of the 4.6 to 5.1 megaHertz segment of the short wave spectrum
will make possible nice catches, because at that time there is minimal
ionospheric absorption and the daily distribution of thunderstorm activity
is also at a minimum... One not too nice thing happening to Tropical Band
Dxers is that many of their favorite stations are going off the air, due to
many different reasons, among them the rapid development of FM broadcast
stations in areas forming served by Tropical Band broadcasts, and the high
cost to broadcaster of keeping on the air old vacuum tube transmitters for
which replacement parts are more and more difficult to find, and when found
are extremely expensive. Cuba uses the Tropical 60 meters band for providing
a nationwide service to so called silence zones, especially in the mountain
regions, where AM and FM broadcasts do not reach or provide a very
unreliable service. That's whey the Cuban Broadcast Institute now operates a
new 50 kiloWatt high tech transmitter for broadcasting Radio Rebelde's
network national program on 5025 kiloHertz, using a near vertical incidence
sky wave antenna system to provide optimum service up to a distance of 1000
kilometers around the transmitter site... For Dxers there is a bonus... the
antenna does have a small low angle lobe that makes possible listening to
Radio Rebelde in many far away places too!!!
......
Si amigos, we do QSL, we do verify reception reports and absolutely free of
charge... You may send your detailed reception reports and comments about
this and other RHC programs to arnie@rhc.cu ,again arnie@rhc.cu , or VIA AIR
MAIL send a postcard to Arnie Coro, Radio Havana Cuba, Havana, Cuba... And
now la numero uno, the number one most popular section of Dxers Unlimited,
ASK ARNIE is on the air... Today's question sent by listener Ivan from near
Moscow. Russia, Ivan wants to know how he can find the equivalents of solid
state devices, so as to make a cross reference between Russian electronic
components and those made in Europe, the USA and Asia... Amigo Ivan, you are
facing a huge problem and quite a challenge... because the specification of,
for example, bipolar transistors for low signal levels are difficult to
match between manufacturers. Fortunately, there are some general purpose
devices that provide a high degree of compatibility, for example I have used
here Russian made KT315 NPN low signal transistors to replace many different
types made in Japan and Europe with excellent results... I also have created
a database that matches to the best possible degree the specifications of
many Russian vacuum tubes to their US, Japan and European equivalents...
Second QUESTION... Came from Canada, listener George from Vancouver, is
asking about the possible efficiency for short wave reception of a TTFD
antenna that will be only 10 meters or about 33 feet long, as that all the
space he has for his antenna system. Well amigo George, here is an important
piece of information regarding the TTFD antenna design... the lower cutoff
frequency for transmitting is calculated very easily by simple arithmetic...
the TTFD length is calculated by diving the wavelength by the number three..
 so your antenna only 10 meters in overall length will be good for
transmitting from 30 meters up... In other words, if you divide 30 meters by
3, your answer will be 10 meters, and that's the length of a TTFD that will
be useable for transmitting from 10  megaHertz up... But now the good news,
a 10 meters or 33 feet long TTFD will be a quite useful receiving antenna
down to about 5 megaHertz !!! So , summarizing, the answer to your question
is, SURE, go ahead and build and then install your 10 meters long TTFD, as
per the building instructions that I have provided, and then after using it
for a while, please tell me and other Dxers Unlimited's fans around the
world about your results !!! AND remember that the TTFD Antenna's most
recent version requires a terminating resistor between 800 and 950 or even
one thousand ohms, that it must be a non inductive type of resistor and that
it should be properly protected against the weather elements. For
transmitting, the TTFD terminating resistor must be rated to a minimum
dissipation of one fourth of the transmitter power for average use, and a
higher rating if you plan to use full carrier modes like standard RADIO
TELETYPE...
....
And now amigos just at the end of the program, as always here is our
exclusive and not copyrighted free for all radio hobby enthusiasts worldwide
..Arnie Coro's Dxers Unlimited HF plus low band VHF propagation update and
forecast...The effective sunspot number, ESN, has gone down dramatically to
below 20, and the actual sunspot optical count was 14 on Friday, an
indication of very low solar activity. The daytime maximum useable frequency
curve is barely reaching 18 megaHertz on the East-West daytime paths, and as
expected, best HF propagation conditions continue to be available just after
local sunset and well into the evening hours. Expect more sporadic E layer
openings, with possible 10 and 6 meters band openings. Atmospheric noise
levels are at a pretty high level, as typical of the northern hemisphere
summer months... Hope to have you all join me next Tuesday and Wednesday UTC
days for the mid week edition of Dxers Unlimited, and don't forget to take a
little time and send me your valuable comments and opinions about this
program, to help me make it better for you and all listeners around the
world !!!


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