DXERS UNLIMITED
Dxers Unlimited's mid week edition for 24-25 June 2003

By Arnie Coro

radio amateur CO2KK




Hi amigos radioaficionados around the world ! You are now listening to the mid week edition of your
favorite listener oriented, and technically minded radio hobby program... I am Arnie Coro , radio
amateur CO2KK, your friend in Havana and host of this show , a program that is devoted to promotion
and development of our wonderful hobby, yours and mine:RADIO !

Item one: Many nice reports about the new RHC Pacific Coast of North America antenna... Thank's
amigos to you all for taking the time to monitor our signals and then sending such detailed reports
that have made our engineering staff and yours truly very happy persons indeed ! Cuba radio
broadcasting is undergoing the most significant upgrade in the past 20 years, and that includes our
nation's AM medium wave broadcasting facilities, the FM stations, the already existing two national
TV networks, plus the new nationwide Educational TV " Canal Educativo", a fourth yet to be named
national TV network still to be named, and of course Radio Havana Cuba too... So in the not too
distant future many of you RHC listeners will begin to pick up our station with much better signal
intensity and also much better audio quality, as the new equipment comes on line....

Item two: Amateur radio's next contest going to take place this weekend, and you will be able to
hear several Cuban station's operating during the ARRL Field Day... Item three: Feedback about the
quadruple diode AM detector continues to reach me at my arnie@rhc.cu e-mail address... Reports of
how well it works are coming from all around the world, and YES, many Dxers Unlimited's listeners
are amazed to be able to pick up short wave signals with just a tuned circuit, four diodes and a few
capacitors, plus a pair of high impedance headphones. During the local morning hours here in Havana,
I can pick up with my 4 diode crystal radio two very powerful short wave relay stations on 15170 and
15190 kiloHertz, but as expected, the crystal radio doesn't have enough selectivity to separate them
very well... Usually I am able to listen quite well to 15190 kiloHertz when they are all alone by
themselves earlier in the morning, but once 15170 kiloHertz goes on the air, the two stations can be
heard at almost the same volume !!! Night time reception with the 4 diode crystal radio is also
fascinating, realizing that this receiver uses absolutely no power source... all the audio
recovered, the one heard on the headphones is supplied directly by the arriving signal without any
amplification whatsoever !!! Amazing as it may sound... that's the way it happens amigos, the MAGIC
OF RADIO !!! Item four: The new generation of totally solid state, no moving parts audio recorders
is opening up the possibility of continuos recording while you tune your radio, without having to
worry about how much magnetic audio tape is used... a combination of the solid state no moving parts
recorder, using sophisticated computer technology and a standard desktop computer will allow you to
keep a very nice library of all the stations you log ... but, the new generation recorders are still
pretty expensive, as compared to standard cassette tape machines !!! Item five: The antenna topics
section today will be featuring the complete detailed instructions on how to build a wire dipole
antenna that provides continuos coverage from 6 to 30 megaHertz, when connected to your radio via a
simple PI network antenna tuner, that's our main feature for today. Then the popular ASK ARNIE
section of the show will be answering another radio hobby related question to add to your data bank,
and as always at the end of the show, have your notepad or tape or solid state no moving parts
recorder at hand to pick up Arnie Coro's Dxers Unlimited's HF plus low band VHF propagation update
and forecast... Margarita Delgado is my sound engineer and producer , stay tuned, our program
continues in just a few seconds.




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>From Havana, for the past 42 years on the air , and now also on the web you are listening to Radio
Havana Cuba, the name of the show is Dxers Unlimited, and here is item five in detail: Imagine a
simple, easy to build , rather low cost short wave antenna system that can be used both for
receiving and transmitting, and that you can build yourself... Well , that's Arnie Coro's SUPER FAN
DIPOLE, an antenna made with six wires and thirteen insulators... Each wire is exactly 10 meters
long, the six of them are identical. Each wire has two ceramic or Teflon or Polyethilene insulators
installed at one end, with a length of about 30 centimeters of Dacron rope between them... The three
wires forming one leg of the dipole are tied together and soldered, and then they are tied to one
side of the center insulator of the dipole. The two sides are identical . You will then solder an
open wire transmission line of around 400 ohms impedance . The open wire line minimum length should
be no less than 12 meters. The antenna is installed between two masts or towers, and you will run
the center wire of each side of the dipole horizontally, while the other two wires are installed so
that one goes above the center wire and the other one below it.

The upper and lower wires are spread so that they form the sides of a triangle, that has a length of
10 meters on the two long sides, and a length of between 3 and 5 meters for the short side... This
configuration is known as a FAN DIPOLE, because the wires FAN OUT from the center insulator. In
actual practice the antenna behaves as a half wave dipole on the 40 meter amateur band, and then
from 7 megaHertz up it starts to provide small amounts of gain. Because of the large surface formed
by the triangles, the antenna behaves as a broadband device, somethint that makes tuning a lot
easier.

The open wire transmission line is connected at the far end from the antenna to a 4 to 1 balun or
balanced to unbalanced transformer, and from the balun to your receiver or transceiver , you install
a length of either 50 or 75 ohm coaxial cable... NO, you heard it right... you can use either 50 or
75 coaxial cable without having to worry for the possible mismatch. BUT from the antenna tuner to
your radio, be sure to use 50 ohm cable !!!

An unsual feature of my SUPER FAN DIPOLE, is that it doesn't need any kind of adjustments whatsoever
!!! You just install the antenna, connect the open wire transmission line to the 4 to 1 BALUN, and
then connect the other port of the BALUN via 50 or 75 ohm coaxial cable to the antenna tuner. By the
way the length of coaxial cable between the BALUN and the tuner is not critical at all...Finally
attach your tuner to the receiver or transceiver via a length of 50 ohm cable no longer than about 2
meters or so...

Once properly installed , the SUPER FAN DIPOLE is an antenna that will provide many years of service
amigos !!! I recommend using the best possible materials... Solid flexible copper wire of number 14
or better yet number 12 or 10 gauge... The open wire transmission line should be made also using at
least number 14 gauge bare copper wire....If you are worried about the BALUN, let me make it clear
that for receiving purposes and low power transmission, the BALUN is also very easy to homebrew and
will cost practically nothing !!!

Yes amigos, si my friends, oui mes amis !!! Arnie Coro's SUPER FAN DIPOLE puts a lot of wire on the
air to catch those incoming radio waves...no less than 60 meters or almost 200 feet of wire will be
working for you up there !!! The open wire line spreaders or insulators can be made from half inch
thick walled CPVC plastic plumbers pipe, or you can shop around for the old timer's favorite dog
bone ceramic insulators , especially made for the open wire ""ladder line "".

The SUPER FAN DIPOLE works nicely from 6 megaHertz and possibly down to 5 megaHertz, and all the way
up to 30 megaHertz. So it is an excellent antenna for both short wave listening and amateur radio
work, when only one antenna can be installed at a particular location. If you want to know more
about Arnie Coro's SUPER FAN DIPOLE, just drop me an e-mail to arnie@rhc.cu, or send me an AIR MAIL
POSTCARD to Arnie Coro, Radio Havana Cuba, Havana , Cuba...




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Coming to you from Havana, via shortwave and also via streaming world wide web audio, this is the
mid week edition of Dxers Unlimited, your favorite radio hobby program: Question: Arnie why don't
you provide us listeners with lists of short wave stations to pick up : ANSWER: Because what may be
my nice list of stations picked up here in Havana , will mean almost nothing to a listener in
Alaska, or New England or Newfoundland !!! I am sure that now you realize that those long lists of
stations provide by some Dx programs are to say the least a waste of time, as HF propagation is site
dependent, and what may be a very accurate list in Texas or Oklahoma will prove to be useless in
Europe, just to give you an example... Now question number two in our ASK ARNIE section of the
program: QUESTION: Arnie Coro, I have found a source of free 75 ohm coaxial cable, and want to know
if I can use it with my 50 ohm input radios ? Signed Bob , a radio amateur operator in British
Columbia, Canada. Well amigo Bob, a few years ago I wrote an article for CQ-VHF Magazine, explaining
in detail how radio amateurs could benefit from the lower cost and even zero cost of 75 coaxial
cable reel ends from CATV, cable TV distribution systems. In my article I described the so called
co-tangent transformer, a device that transforms the impedance of 75 ohm cable to 50 ohms.But the
co-tangent transformer is a single band device.... Although it makes possible to install 6 meters or
2 meter band antennas using low loss large diameter cable of the type that the TV distribution
systems use. The ends of the drums are of little use to the Cable TV companies and they usually can
be obtained at very low cost or even for free from the technicians that install and mantain those
systems.

Using a simple PI network antenna tuner , you can install 75 ohm coaxial cables with the PI network
providing an almost perfect match to 50 ohm equipment.

And now amigos , as always at the end of the show , here is Arnie Coro's Dxers Unlimited's HF plus
low VHF band propagation update and forecast . Geomagnetic conditions to be disturbed, actually the
three hourly K index was up to 5 early morning local time in Havana Tuesday. And the A sub P or
planetary geomagnetic disturbance indicator was above 20 also.

I really have had not much time to monitor for sporadic E events since Friday, but during the few
checks that I have made, no signs of openings were detected, although we are certainly now at the
peak of the summer solstice sporadic E season. Expect rather nice night time HF propagation on
frequencies as high as 18 megaHertz, and that means that both the 20 and 17 meters amateur bands
could provide some nice evening QSO's. A bandscan of the 19 meters international short wave
broadcast band late evening Monday showed a significant number of Dx stations present with pretty
nice signals . For those of you wanting to work round the world Dx, here is your friend's Arnie Coro
advice: Set your alarm clock for around 5 o'clock in the morning your local time , as minimum
ionospheric absorption conditions to the South and West of your location will be happening between
roughly 5 AM local time and sunrise.

See you at the weekend edition of the program, which is going to be a pre-recorder on Friday show,
because during the weekend I will be joining a ham radio contest station to enjoy this wonderful
hobby in yet another of the more than 70 ways you and I can have a very good time playing with our
radios amigos... Send your signal reports and comments to arnie@rhc.cu, or VIA AIR MAIL to Arnie
Coro, Radio Havana Cuba, Havana, Cuba.