Radio Havana Cuba

Dxers Unlimited

Dxers Unlimited's weekend edition

By Arnie Coro

radio amateur CO2KK

Hi amigos radioaficionados around the world now listening to the weekend
edition of your favorite radio hobby program, the one and only that
brings you information and comments about all aspects of our wonderful
way of enjoying our spare time... I am Arnaldo, Arnie, Coro, radio
amateur CO2KK , and as always its my pleasure to share with you about
seventeen minutes of on the air, and on the world wide web time too...
You can also read the scripts of this show by subscribing to the Ontario
DX Association mailing list.. Now here is item one: Very nice HF
propagation conditions will be prevailing during the rest of this
weekend and they will be extending from Monday to perhaps Thursday of
next week, when we may see some changes. November in the northern
hemisphere brings the lowest height of the F2 layer , and that has a
beneficial effect on short wave propagation... The Sun has not been
quiet at all... and several rather large sized sunspots can be seen on
the solar disk... Item two: Radio hobby related experiments are one of
the nice ways of enjoying our spare time, and sharing it with other
radio amateurs , short wave listeners, TV Dxers etc... Some radio
experiments generate quite surprising results, as once when I was
testing a 10 meters band transceiver using a light bulb as a dummy
load... I was saying hello, hello into the microphone, and when I
released the push to talk switch , suddenly I hear someone calling me...

It was a radio amateur located about 10 miles away that was hearing my
test... and amazing as this may sound, the coaxial cable to the light
bulb dummy load was radiating enough signal to be heard at such a distance..

Another funny anecdote happened during last year's summer sporadic E
season, when I was tuning around 49.9 megaHertz looking for FM point to
point systems that usually tell you that the band is open, and I picked
up a cordless phone conversation that was taking place in Mobile,
Alabama !!! Amazing, but perfectly possible when a very intense sporadic
E layer is located at the right place and at the right time.

Stay tuned for more radio hobby related items coming up as Dxers
Unlimited's weekend edition continues in a few seconds... I am Arnie
Coro in Havana, and my e-mail address is arnie@rhc.cu

.......

You are listening to Radio Havana Cuba, the name of the show is Dxers
Unlimited, it's on the air twice weekly with the most up to date short
wave propagation update and forecast , always coming up at the end of
the program. Now here is item three: CM2IRG my good friend and neighbor
Reynaldo, will be taking his amateur radio test to upgrade his license
to the first category...so soon he will be CO2IRG... and for those of
you that have asked about the 3 letters in the suffix of Cuban amateur
radio calls that are now so common, the reason they are in use is that
the combinations of two letters for the callsigns in many of our call
areas were exhausted, so the licensing authority had to move to the
three letters suffix in the City of Havana number 2 call area and also
in other of the 8 call areas in use. Here in Cuba the number 9 call is
reserved for radio club stations,and the number zero is only used for
special event stations...

Amateur radio exams take place twice yearly, and radio clubs all along
the Cuban archipelago provide newcomers with a basic course that lasts
40 class hours.

Upgrades to second and first class licenses tests are also carried on
twice yearly... The Cuban Federation of Radio Amateurs, the umbrella
organization that provides the legal framework as a non government
organization to the nations radio clubs has now a membership or slightly
more than 5000 ... an outstanding increase that shows the great interest
that amateur radio has among the Cuban people...

Item five: You always ask for this one when writing, as it seems to
provide many Dxers Unlimited's listeners around the world with answers
to questions they were thinking about !!! Here is ASK ARNIE, la numero
uno, the number one most popular section of this twice weekly Radio
Havana Cuba show... ASK ARNIE today will be answering a question sent by
listeners from seven nations... Mexico, the USA, Canada, the United
Kingdom, South Africa, New Zealand and Australia... They all want to
know more about compact antennas for the lower frequency bands... and
this question came as a follow up to a recent explantion I gave here
about how the solar cycle's expected behavior during the next year and a
half or so... So , here we go amigos...

For low frequencies reception , in the range between 2 and 10 megaHertz
one of the best approaches is to homebrew a magnetic loop antenna, that
can be made using the outer shield or braid of a medium size coaxial
cable , like RG 8 or RG213... Placing the coaxial cable to form a square
around a wooden or PVC plastic frame will provide you with an excellent
receive only antenna if the diameter of the support is no less than one
and a half meters... In other words you want a rather large sized loop
that can be easily tuned using an air spaced variable capacitor to which
you can connect other high quality silver mica capacitors in paralell to
lower the resonant frequency of the antenna. This magnetic loop antenna
can be placed indoors or outdoors... but if you locate it far from the
receiver, then one of its benefits will not be easy to use, because you
will have to go to where the antenna is located and then move it to
obtain either a signal maximum or to null out a noise source, a most
valuable feature of the magnetic loops for people living in heavily
populated areas where computers, tv sets , furnace controls and other
electronic equipment generated a lot of radio frequency noise.

Be aware that I am talking about a receiver only magnetic loop, that
does not require the use of a high voltage rated variable capacitor...,
transmitting magnetic loops do require using extremely high voltage
rated capacitors, even when your amateur station is running at low power
levels !!

A lot of information about magnetic loop antennas can be found by
surfing the world wide web, and one of the big advantages of this type
of antennas is that they can be made at low cost and with readily
available materials...

Transmitting loops are typically made of rather large diameter copper
tubing that has to be welded to assure a very low ohmic resistance, as
the current circulating on the loop can be extremely high, again even
with rather low power transmittters...

Si amigos, yes my friends... prepare for the really low ebb of the solar
cycle, due to last until the end of 2007 by homebrewing a nice tuneable
magnetic loop antenna so that your radios can pick up the signals on the
frequency range between 2 and 10 megaHertz that are going to be the ones
available most of the time during this tail end of solar cycle 23 !!!

.......

Dxers Unlimited's weekend edition continues now with another popular
section of the program...visiting the workshop.... It may be one of
those rare opportunities when my workshop is really well organized, but
today, the workbench has only two projects in progress...

One is yet another REGENERODYNE receiver, that is now almost finished...
I have already tested the power supply, and the audio amplifier
module... and the regenerative detector that operates from 1.7 to 3.7
megaHertz still needs some finishing touches,but it is basically working
OK,providing very smooth regeneration , because this is my favorite
Hartley pentode circuit that controls regeneration by variying the
screen grid voltage... What I want to complete by Monday is the front
end of the regenerodyne, that is quite a departure from previous
designs... This one uses a group of computer clock TTL oscillator
modules for the local oscillator , and a solid state four diode double
balanced mixer...This is a radically different approach from the now
standard pentode RF amplifier and dual triode mixer that I have used for
years in these receivers.

So, in about two or three weeks, after this version of the regenerodyne
receiver is working,I will be sharing with you Dxers Unlimited's amigos
my impressions about the performance of this new radio. For your
information, the computer clock modules came from defunct computer
motherboards... and I have already soldered in place five of them...
With the 8.0 megaHertz module, the one I will be using for the initial
tests, the receivers tuning range

will be from 9.7 to 11.7 megaHertz by adding the 8 megaHertz to the
regenerative detector's tuning range, and from 4.3 to 6.3 megaHertz but
the tuning will be in REVERSE mode, with the 4.3 megaHertz received at
the 3.7 megaHertz setting of the regenerative detector... This tuning
range was selected because most of my workshop time is after 10 pm in
the evening, and at that time short wave propagation on frequencies
above 10 megaHertz is not very good... I am sure that the new receiver
will be capable of picking up stations on the 60 meters Tropical
Broadcast Band, and of course, the high power stations on the 6
megaHertz or 49 meters band.

This new version of the REGENERODYNE receiver is totally modular, so
that it can be used for both experimenting and demonstrations to would
be builders that are frequent visitors to my CO2KK amateur radio station...

And now amigos,as always at the end of the program here is our exclusive
HF propagation update and forecast... Solar activity will continue to be
at very low to low levels, and no signs of higher activity are seen at
this moment. The solar flux is rather stable at around 90 units with a
very low A index, something that, as I said at the start of the program
will certainly have a positive influence on HF propagation conditions,
but be aware that the after local sunset decline in the maximum useable
frequency is going to be rather steep... Best bands for amateur radio
Dxing this weekend and during next week are going to be 17 meters and 20
meters during the daytime, and 80, 40 and possible 30 meters during your
local evening hours... Amigos, I do appreciate very much your comments
about the program, and it is always nice to offer a helping hand to
fellow radio enthusiasts if you have any questions concerning your
equipment, antennas, or about homebrewing radios... send mail to
arnie@rhc.cu or VIA AIR MAIL, send a post card or letter to Arnie Coro,
Radio Havana Cuba, Havana , Cuba