Tuesday -Wednesday, January 15- 16, 2008
Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited's mid week edition for 16-17 January 2008
By Arnie Coro
radio amateur CO2KK

Hi amigos radioaficionados , welcome to the mid week edition of your
favorite radio hobby program... I am Arnie Coro, radio amateur CO2KK and
as always it is my pleasure to share with you around 17 minutes of on
the air and on the web time. You can also read the scripts of the show
by subscribing to one of the several short wave listeners and radio
amateur's mailing lists to which the scripts are uploaded sometimes even
slightly ahead of our first on the air delivery. Among the lists that
carry Dxers Unlimited's scripts are the ODXA , Ontario DX Association
Yahoo groups list, the ANTENNEX antennas topics web magazine e-mail
distribution list . Now here is item one of today's program: Although
practically all solar scientists coincide about the fact that solar
cycle 24 has already started, we have yet to wait for a while longer to
see more high latitude , reverse magnetic polarity sunspots that belong
to cycle 24... so far optical observations have picked up just one small
sunspot group that everyone is practically sure that it belongs to the
new cycle... In the meantime, the latest solar data shows a blank Sun,
zero sunspots and a very low solar flux. More information about HF
propagation conditions , as always at the end of the program. Item two:
I have received many requests to post the whole set of data files for
the Regenerodyne receivers family and the Super Islander hybrid amateur
radio transceiver. At this moment I am working on the circuit diagrams ,
so that when the files are made available, those of you interested in
duplicating the circuits will then have available very detailed circuit
diagrams, photos and the complete step by step building instructions,
following the patterns of the well written radio kit manuals, with the
exception that you must look for the parts all by yourself . Item
three: Monitoring the 19 meters international broadcast band during the
local early morning hours is an excellent demonstration of how the
maximum useable frequency curve rises very slowly under conditions of
very low solar activity. Even on short paths , single hop propagation,
the 15 megaHertz band is not able to provide a high quality service
until the Sun is way up above the horizon. Our own Radio Havana Cuba
morning show, Despertar con Cuba, waking up with Cuba is not on the air
on 19 meters until 13 hours UTC, that is 8 AM local time here, and the
reason for operating on 6180 kiloHertz from 11 hours UTC to 13 hours UTC
and then switching to frequencies on the 22 meters band and the 19
meters band is precisely to make the best possible use of the
propagation windows that don't open up until the ionosphere has received
a good boost of solar ultraviolet radiation. By the way if you want to
practice your Spanish , our Waking up with Cuba show, Despertar con Cuba
is an excellent opportunity to get a daily practice session of Spanish
language. You can pick our morning show in North America from 13 to 15
hours UTC on 15370, 13680 , 12000 and, 11760kiloHertz, as all
frequencies that can be well heard in North America during that two hour
period . Stay tuned for more radio hobby related information , coming to
you from Havana, when our mid week edition of Dxers Unlimited continues
after a short break for station ID...

.......

You are listening to Radio Havana Cuba, the name of the show is Dxers
Unlimited, and here is now our next item of today's program: Our popular
Antenna Topics section, that today will feature information about
underground antennas, an option that is a good choice when you do have a
garden or backyard area available, but for some particular reason or
reasons you can't install antenna masts or towers. Amazing as this may
sound, undeground antennas for the short wave bands do work, and when
properly designed and installed the results achieved with them are
really amazing. One of the interesting features of underground antennas
is that they can provide a very good signal to noise ratio , as they are
actually shielded from noise sources that make reception difficult. I
have tried two different types of underground antennas for short wave
reception and transmission. One of them is made from a length of coaxial
cable that you don't even have to bury underground, but that it is
always a good idea to put it below ground preferable inside a length of
buried PVC or polyethylene pipe. This antenna type is often refered as a
" SNAKE ANTENNA" because of the way the black coaxial cable looks when
lying on the ground. I have also installed SNAKE antennas on my
reinforced concrete rooftop, with very good results, comparing the
signals received from the SNAKE ANTENNA with signals picked up with a
FAN DIPOLE located about 10 meters above the SNAKE made with a 15 meters
long length of RG213 coaxial cable , terminated with a 50 ohms resistor.
This version of the SNAKE ANTENNA is used for both receiving and
transmitting. Using a 100 Watts 50 ohm dummy load at the end of the
SNAKE ANTENNA, this 15 meters long length of coax provides, as expected,
an almost perfect match for the transmitter's output stage. Radiation
efficiency is pretty low, but it does radiate, and makes two way
contacts possible especially on 80 and 40 meters using the Near Vertical
Incidence Skywave propagation mode that is so useful for handling
emergency communications traffic.
The SNAKE ANTENNA can also be installed below ground, with a depth of
between 10 and 30 centimeters been typical. For those of you that don't
think in Metric, that's between 4 and 12 inches below the ground. The
SNAKE ANTENNA made of RG213 coaxial cable goes inside a 25 millimeters
or 1 inch diameter PVC pipe, and you will need a well sealed box to
house the terminating resistor. If you are going to use the SNAKE
ANTENNA only for receiving , then my advice is to use a two parallel
connected 100 ohms at 2 Watts carbon non inductive resistors, but if you
plan to use the antenna with the typical 100 Watt power class amateur
radio transceiver, then you will need to install a 100 Watt non
inductive resistor at the end of the 15 meters length of coaxial cable.
Now for those you that are still puzzled about the SNAKE ANTENNA, let me
explain that the 15 meters length of RG213 cable is connected to your 50
ohms coaxial transmission line from your receiver or transceiver in the
following way: now pay special attention: The inner conductor of your
coax transmission line is connected to the outer shield , that is the
braid of the SNAKE ANTENNA coax, and the shield of your coaxial
transmission line is connected to the inner conductor of the SNAKE
ANTENNA...
When you run the first test of the SNAKE ANTENNA for receiving, having
the antenna just lying on the ground, you will notice that the noise
level if very low, as compared with the noise level picked up by a
standard elevated type of antenna system. As many users of the SNAKE
ANTENNA have found out, at some particular locations, they can actually
pick up more stations and with a better signal to noise ratio using this
unique antenna system, even when it is buried at a typical depth of
about 30 centimeters or 12 inches below ground.
Another type of underground antenna that has seen use by professional
communications systems, consists of a center fed dipole contained inside
a 15 centimeters or 6 inches diameter PVC pipe, that is equipped with an
automatic antenna tuner located inside a box that is also buried next to
the antenna's feed point. Such a system has less losses than the SNAKE
ANTENNA, but is much more expensive to build and install, a
consideration that is not very important for some professional users of
such stealth antenna systems.
As you may realize, even with extremely tight restrictions by landlords
and owners associations, those dreadful CCR's that are becoming more and
more frequent, it is possible to bypass them by digging a trench in your
garden, installing an underground antenna and maybe combine it with a
nice looking flagpole stealth vertical or a beautiful elevated bird
feeder, so you can cover the VHF and HF bands without any "actual
antenna in sight "...
......
QSL on the air, QSL on the air to amigo Paul Brown VE3SU, who sent me a
very nice report from Lake Erie shores... Paul told me in his e-mail
that our 6000 Kilohertz signal was loud and clear at his location, where
he is , like many other radio amateurs, using his ham radio transceiver
feature of having a general coverage receiver included , to enjoy short
wave listening too... Thank you amigo Paul, and keep listening to my
show !!! Item six: As I said at the begining of today's program, the
maximum useable frequency curve was showing a very slow raise Tuesday
morning local time... At fifteen minutes before 10 AM local time, that
is 14 hours 45 minuts UTC, a bandscan of 19 meters from 15.000 the
frequency of WWV, standard time and frequency station up to 15 500
kilohertz , brought just two signals with a 55555 SINPO report, with
the rest of the seventeen carriers detected not providing really
readable broadcast quality signals. It is accepted standard practice
that for broadcast quality reception of amplitude modulated signals you
need at least 26 decibels of signal to noise ratio, something that was
only achieved Tuesday morning in Havana on the 19 meters or 15 megaHertz
international broadcast band by two stations, our own local signal of
Radio Havana Cuba on 15370 kiloHertz until signoff at 15 hours UTC and
China Radio International on 15230 kiloHertz. By the way the antenna I
was using for this test is a fan dipole with 10 meters long legs , fed
with balanced line and connected to the receiver by means of a Kenwood
AT-200 antenna tuner. The receiver used was the Kenwood TS-820
transceiver, that has a position on its bandswitch that allows reception
of a band from 15000 to 15.515 kiloHertz. And now amigos, just before
going QRT, here is our exclusive , but not copyrighted, in the public
domain HF propagation forecast... Solar activity at very low levels,
with the sunspot optical sunspot count at ZERO... Slight propagation
disturbances at latitudes above 40 degrees North, and don't expect
sporadic E events, as the winter E skip season is just over now. I
expect nice AM broadcast band DX conditions for Tuesday and Wednesday
evenings local time...So, relax, and just wait a bit more for sunspots
from cycle 24 to begin populating the solar disk and improving short
wave propagation amigos !!!! Don't forget to send your signal reports
and comments of today's program to arnie@rhc.cu, of VIA AIR MAIL, send
me a postcard to Arnie Coro, Radio Havana Cuba, Havana, Cuba