Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited's weekend edition for 21-22 January 2006
By Arnie Coro
Radio amateur CO2KK

Hi amigos radioaficionados !!! Welcome to the weekend edition of Dxers
Unlimited reaching you while solar activity continues to be at a very low
level and the daily planetary geomagnetic disturbance indicator is also
hitting bottom low figures. Translated to plain language, excellent
propagation conditions for the frequency range from 100 kiloHertz all the
way up to 8 megaHertz. And also that the daily maximum useable frequency
curve is showing a very low peak on even the best paths. So once again, Long
Wave, Medium Wave
And Tropical Band Dxers are enjoying a FIESTA !!! Radio amateur operators
with good antennas for 160 and 80 meters are also having a great time too
!!!
Item two: Is Ten meters a dead band nowadays. that was a question sent in by
a listener who owns a Radio Shack -UNIDEN HTX100 transceiver. and he
answered the question for me by writing in his e-mail that monitoring ten
meters
Beacons on a regular basis has shown him that ten is open much more than
what anyone would expect. For example, even when the solar flux was just
barely above 80 units and the sunspot count for the day was ZERO, amigo
Charles was able to work no less than fifteen DX stations with his 25 Watts
rig and a very nice Bobtail wire antenna. So, follow Charlie's advice and
monitor the segment of 10 meters between 28.1 and 28.3 megaHertz looking for
beacons that will tell you for sure that the band is open !!!
After receiving Charlie's e-mail, I started to look for an odd length of
coaxial cable and three insulators plus some copper wire to install a
monoband antenna for 10 meters, because, by coincidence I happen to also own
an HTX100 that was partially retired here after the last peak of solar cycle
23 !!!
Item three: Your e-mail messages with your personal experiences with short
Wave and VHF or UHF propagation, or those you have enjoyed by homebrewing
equipment and using it , as well as radio hobby related questions are most
welcome amigos.send them so that I can share them with other Dxers
Unlimited's fans around the world. Send mail to arnie@rhc.cu, again
arnie@rhc.cu, or send a letter or postcard VIA AIR MAIL to Arnie Coro, Radio
Havana Cuba, Havana, Cuba.
Dxers Unlimited's weekend edition continues in just a few seconds, after a
short musical intercut.
..
Si amigos, yes my friends. This is Radio Havana Cuba, the name of the show
is Dxers Unlimited, and for those of you first time listeners, let me inform
you that this is a twice weekly program totally devoted to the promotion and
development of our wonderful hobby. RADIO.. Here is now item four: A nice
software program for almost instantly calculating MAGNETIC LOOP ANTENNAS
that works on any computer with WINDOWS 98, WINDOWS 2000 or WINDOWS XP is
now available as freeware. The program has a very user friendly interface,
and lends itself to experimenting with changing the parameters of the loop
in order to see what happens when you do so. Three shapes of the loop are
possible, an OCTOGON or eight sided loop, a CIRCLE, which is the ideal
optimum shape, and the somewhat less efficient but sometimes easier to
homebrew square shaped loop. It is really surprising to see how efficient
one of these small magnetic loop antennas can be, and how the tuning
capacitor requirements may be easily met with simple rather easy to make
capacitors that consist on lengths of coaxial cable. By the way, a receive
only magnetic loop can be tuned with a standard variable capacitor, as no
high radio frequency voltage will be present in that antenna system. Using
this nice easy to understand and user friendly software I designed a receive
only loop for the frequency range between 10 and 30 megaHertz, and for your
general information here are this antenna's main parameters.
Frequency range design target : 10 to 25 megahertz, that is from 30 to 12
meters wavelength
This one has a Loop Circumference of 3.30 meters, and is a square shaped
loop made with copper wire of 3 millimeters in diameter. Tuned to 10
megaHertz by a capacitor of 50 picofarads it will provide excellent
reception of the 30 meters or 10 megaHertz amateur band.
The same loop will tune continuosly up to 25 megaHertz, by just turning the
variable capacitor.
I used here a variable capacitor with a maximum measured capacitance of
55 picofarads, and with the capacitor plates fully out, the antenna tunes
to 23 megaHertz..
By the way the lower you tune the antenna in frequency, the efficiency will
go down, but this is only really important for a transmitting antenna.
I invite you to experiment with this easy to use magnetic loop antenna
calculator, just send me an e-mail to arnie@rhc.cu and I will send you
a reply with an attachment consisting of a virus free file with the LOOP
CALCULATOR program. I am sure that after receiving it and experimenting for
a while, you will end up assembling your own magnetic loop antenna for
receiving.
...

QSL on the air, QSL on the air to the many Canadian listeners that are
members of the Ontario DX Association , who have sent e-mail messages asking
for the posting on the ODXA YAHOO LIST of Dxers Unlimited's scripts.
OK amigos, I will re-start posting the script of the day with this weekend
edition of the show !!! QSL on the air , also to the radio amateur operators
that I have recently met on the air while operating on the PSK31 digital
mode. to them the bad news is that the sound card of the 486 machine I was
using for PSK31broke down, and so far all efforts made to repair have
failed.Finding an old 16 bit ISA slot Sound Blaster sound card has proven to
be impossible so far, so as soon as I find one, CO2KK will be back on the
air on PSK31 and standard
Radio Teletype. In the meantime my ham radio station will continue to be on
the
Air on the HF bands on CW and Single Side Band modes.

Item six: Try listening this weekend to contest activity on 160 meters. use
your radio with the BFO on, and tune slowly for amateur radio stations that
will be participating in the contest.But be aware that without a really big
external antenna , reception on 160 meters is confined to local and very
powerful DX stations.I'll be monitoring 160 meters from about zero hours UTC
about 6 hours UTC Sunday, and will make an attempt to load my inverted L
antenna on that band.The antenna is really too short to be efficient, but
under the excellent propagation conditions expected, maybe I could work a
few nearby
Stations !!!
...
Item seven: Here is Dxers Unlimited's techinical topics section. Today I
will tell you about yet another easy to homebrew low take off angle antenna,
especially suited for working DX on the bands from 20 meters to 10 meters.
My experiments with a model BOBTAIL built for the 2 meters band proved
to be really succesful, and I am now gathering all the materials to homebrew
a much more well built one, as the experimental model left a lot to be
desired from a mechanical point of view.The BOBTAIL is a vertical antenna
system
with a low take off angle , using three radiating elements .It is voltage
fed at the bottom of the center element, and according to both antenna
modelling software and actual practical field measurements, this simple,
easy to build antenna has a 9 db gain over a half wave dipole reference
antenna .This antenna produces a bidirectional pattern, that can be used to
good advantage when you want to work DX into certain areas.





My two meters band test antenna allows me to access two repeaters that are
located at exactly opposite directions. Prior to the installation of the
BOBTAIL, I had to run the handie talkie at full power to reach the repeaters
but now I can run the rig at the low power setting, a quite useful feature
during emergencies when the radios are running on emergency power.
...
ASK ARNIE, the number one most popular section of Dxers Unlimited will be
answering today a question sent by listener Ivan from Ukraine. Ivan wants to
know more about my HURRICANE ONE single band transceiver, that was
designed two years ago, in order to provide Cuban radio amateurs with an
easy to homebrew transceiver that could be built with easily available
electronic components that come mostly from recycling.
Amigo Ivan, the HURRICANE ONE, or HURACAN UNO in Spanish, uses a direct
conversion receiver, that has an input signal attenuator, a bandpass dual
tuned input filter a cascode radio frequency amplifier , a dual diode
product detector, followed by an audio amplifier chain that features two
audio filters, one for CW and the other one for PHONE signals.. I have
already e-mailed you the circuit diagrams of this simple project , with some
notes about the use of
Eastern European solid state devices that you could probably find locally
In your country.

And now amigos at the end of the program, as always when I am here in Havana
ready to copy Arnie Coro's Dxers Unlimited's HF plus low band VHF
propagation update and forecast. Solar activity will continue to be very low
as cycle 23 continues its downward trend. A solar coronal mass ejection
high speed wind stream may hit the Earth's magnetosphere Tuesday UTC day,
and that will increase the background noise levels on frequencies from 100
kiloHertz to 5 megaHertz. Due to the very low solar activity, expect also
very low maximum useable frequencies, so concentrate your listening time or
your amateur radio operating time on frequencies between 500 kiloHertz and
8 megaHertz. Hope to have you all listening to the mid week edition of Dxers
Unlimited next Tuesday and Wednesday UTC days amigos. And don't forget to
set aside a little of your spare time to send an e-mail with your signal
reports and comments about the program. send mail to arnie@rhc.cu...
Again arnie@rhc.cu, and VIA AIR MAIL send a postcard to Arnie Coro, Radio
Havana Cuba, Havana,Cuba