Dxers Unlimited
Dxers Unlimited's weekend edition for 31 May - 1 June 2003

By Arnie Coro

radio amateur CO2KK




Hi amigos radio and TV aficionados !!! Welcome to the weekend edition of Dxers Unlimited reaching
you when the Earth is still under the impact of one of the worst geomagnetic storms in months !!! A
solar active sunspot region, a single one, but a really big one has kept solar scientists as busy as
you can think, at a time many of them thought that solar cycle 23 was now fully into the low and
very low areas of activity... The A index, the Planetary Geomagnetic Disturbance Indicar, A sub P
went up well past the 40 units mark, and as expected, aurora borealis displays could be seen at
higher latitudes, and both VHF radio amateurs and Medium Wave AM broadcast band Dxers have enjoyed
another extended period of very interesting for them propagation conditions... As a matter of fact,
6 and 2 meter band amateur operators have made lots of contacts, and reports reaching me via the
Internet describe the reception of many AM broadcast stations from South America and the Caribbean
in Canada ... More about the super sunspot group and what to expect during the rest of the week
regarding HF and low band VHF ionospheric propagation at the end of the program, ITEM TWO:
homebrewing of radios is absolutely fascinating, be it the ultra simple yet very effective
AUSTRALIAN FUN RADIO, or a more sophisticated but still simple by commercial standards regenerodyne
receiver. Homebrewing radios using recycled parts adds extra fun to your projects, and helps to keep
them in use for more time . Today I will tell you about several other simple, easy to build at home
radios... ITEM THREE: Its about time for you to install one of my broadband low VHF frequencies
dipoles to be able to enjoy this year's sporadic E skip season... Friday morning, using the
prototype antenna , I enjoyed about two full hours of Managua , Nicaragua CANAL DOS, channel 2 TV,
that was coming in just like a local station via a very intense patch of sporadic E layer
ionization. ITEM FOUR : ASK ARNIE, yes I have decided to change the name of this section of Dxers
Unlimited, as per your request amigos ... Instead of the lengthy YOU HAVE QUESTIONS and Arnie tries
to answer them, it's now a lot easier to remember... send your radio hobby related questions to
arnie@rhc.cu , again arnie@rhc.cu, and don't forget to include in the subject line ASK ARNIE, so
that I will reply back immediately with the answer to your questions... ITEM FIVE will bring Dxers
Unlimited's weekend edition to an end with the most up to date HF plus low band VHF propagation
update and forecast... Margarita Delgado is my sound engineer and producer , I am Arnie Coro in
Havana, back with you in a few seconds...

.....

This is Radio Havana Cuba, the name of the show is Dxers Unlimited and our menu includes not only
Dxing but also items from the more than 70 ways you and I enjoy this wonderful radio hobby... Item
TWO: homebrew radios, yes homebrew radios are a lot of fun, and th thrill the bring to the builder
is second to none... Even the simplest crystal radio, only able to pick up a very powerful local AM
broadcast station a few miles away, involves the absolute magic of radio... and that magic is ever
present whenever you build a new receiver, transceiver, antenna tuner, multimode decoder, or even
that simple interface that allows your computer to now become an essential part of your ham radio
station or short wave listening post !!! Among the most recent designs I have seen, two of them have
attracted my attention, as they make good use of the modular construction concept, so you can start
with a simple circuit and later develop it into a more sophisticated project. For those of you
having the possibility of receiving reasonably sized e-mail attachments, I can send now a very nice
circuit diagram of a universal audio amplifier for homebrew receivers that uses one low noise
transistor and an integrated circuit audio amplifier... The values of the components were specially
tailored for optimum audio frequency response within the range required by voice communications, so
this amplifier, when connected to a standard receiver via the earphone jack, actually improves your
chances of picking up those weak one that make the difference between a log with common entries, and
one with at least one or two real DX stations. You can send for the UNIVERSAL AUDIO AMPLIFIER
circuit diagram , via e-mail, send mail to arnie@rhc.cu, again, arnie@rhc.cu, and specify that you
want the universal audio amplifier circuit diagram. This modular circuit can be placed inside a
medium sized computer speaker box, so that you can also use it as another test instrument in your
radio and electronics workshop... Parts for the UAA, the UNIVERSAL AUDIO AMPLIFIER are very common
and easy to find, so in case something fails , a replacement components is not that difficult to
locate... This amplifier provides room filling volume when used with a loudspeaker of about 6 inches
or 15 centimeters diameter installed inside an acoustic cabinet... If you really want this project
to be complete, place the audio amplifier and speaker inside a wooden cabinet, in order to obtain
the best possible audio quality... Si amigos, yes my friends , oui mes amis... homebrewing radio
gear is a lot of fun, and the UAA universal audio amplifier is one of those projects that can be
completed within one or maybe two weekend, and let me warn you that after you have one up and
running, you will surely want to build the second one, and yet another warning, have the circuit
diagram printed and ready for your radio hobby friends , because once they listen to this one, they
will certainly ask you for Arnie Coro's UAA universal audio amplifier circuit diagram !!!

......

>From Havana, this is Dxers Unlimited's weekend edition, reaching you via short wave , where
propagation conditions are not that good today due to the upswing in solar activity, and also coming
to you via our INTERNET AUDIO stream from www.radiohc.cu, and now amigos, here is our very popular
antenna topics section of the program... The summer sporadic E season is now in full swing, reports
are coming from all over the Caribbean, Central America, North America and Europe that this year's
events are providing much more DX than what was a very dissapointing 2002 summer season... So far,
lot's of nice DX from 25 megaHertz all the way up to 150 megaHertz via sporadic E clouds amigos !!
BUT, if you don't have an external antenna installed, your chances of picking up those nice DX
signals are reduced significantly... So here is my advice: install one of my easy to build broadband
dipoles for the low band VHF frequencies... With the prototype antenna I have worked lots of 6 meter
band ham stations this past week, and also picked up low VHF band TV channels from six different
countries, Nicaragua, Mexico, Guatemala, Panama, the United States, and Puerto Rico, using a
standard TV receiver , without any kind of pre-amplifiers or boosters.. Arnie Coro's broadband
dipole is very easy to build... You will only need a good supply of no 14 or no 15 copper wire ( you
can use standard PVC insulated wire of the type used for wiring home electrical circuits ) three
homebrew insulators and a length of dacron or nylon rope... The antenna is a symmetrical dipole,
both sides are identical... each leg of the dipole is made of six wires that form a cone... The
wires are used to form the skeleton of a cone... that has an overall length of

1.25 meters or just a bit more than 4 feet... As you will figure out immediately, the antenna's
overall length is 2.5 meters , so it is actually resonant at the frequency of 60 megaHertz... but
because of the characteristics of the design, the antenna offers a rather significant bandwidth...
in other words, and speaking now in an easier to understand language for newcomers to the radio
hobby, this antenna will be able to pick up stations that operate between about 40 and 80 megaHertz,
with the center frequency of 60 megaHertz located just in between the upper end of TV channel 2 and
the lower end of TV channel 3 in the Americas... The broadband dipole cone's are made in such away
that at the far end of the six wires, they are attached to a copper tubing circle that has a
diameter of

30 centimeters... So the cone has an aspect ratio of about 4 to 1... that means that this structure
is a little heavy to support, so proper care should be taken when you are installing it... The
antenna is fed via a broadband one to one balun , and then connected to your TV set or radio using
75 ohm coaxial cable...

You can certainly add an antenna tuner and standing wave ratio meter to provide a perfect one to one
SWR to your 6 meter band transceiver, in case you want to use it,as I do here, as a standby or
monitoring antenna for 50 megaHertz DX. This is a typical weekend project, and once installed, the
broadband low VHF antenna will provide many years of service with only a little maintenance... Also,
you will be the proud owner of a beautifully looking antenna system... as it sure looks nice amigos
!!! If you want to know more about this easy to build antenna for TV Dxing and 6 meter amateur band
operation send a postcard to Arnie Coro, Radio Havana Cuba, Havana, Cuba, or send an e-mail to
arnie@rhc.cu...

I will be glad to help you to build and install this nice looking antenna that will add many new
stations to your low band TV Dxing logbook !!!

......

Ask Arnie, Ask Arnie, if you have any radio hobby related questions, just don't keep them to
yourself, Ask Arnie and you will receive a fast answer right at your computer, or a somewhat slower
one to your mailbox !!! The question sent in to our Ask Arnie section of Dxers Unlimited came from
Australia, from the city of Melbourne, where Roger wants to know how is it possible for very weak
low power amateur radio signals from the Caribbean to be heard on an almost daily basis at his
QTH... Well amigo, that's because signals from the Caribbean travel all the way to Australia not via
the regular multiple hop skip propagation mode, but via what is known as ionospheric tilting... In
other words the low power QRP signals don't bounce back and forth five or six times between the
ionosphere and the Earth, but they actually travel within the ionosphere, entering here and coming
down at your QTH, following what is known as the TERMINATOR LINE OR GRAY LINE propagation !!! And I
hope this answers your question, and of course that I will be looking for you on 40 meters at dawn
here in Havana when you will be seeing your local sunset in Australia amigo !!!

.....

And now as always at the end of the show , here is our exclusive and not copyrighted HF plus low
band VHF propagation update and forecast... Expect a very significant number of Sporadic E events
during the next five days... Ionospheric absorption on frequencies between 5 and 20 megaHertz should
be HIGH, and short wave propagation conditions should be severely affected by the impact of the high
speed solar wind that are causing geomagnetic disturbances,that has sent the A index to figures as
high as 50 !!!!.

The big sunspot group that has produced several X class solar flares during the past few days is
expected to continue active, so we must be ready for more solar fireworks !!! As I like to say,
there is no such thing as poor radio propagation, because what is bad for short wave listeners, may
prove to be excellent DX conditions for AM broadcast band lovers!!! Enjoy radio amigos, it's a great
hobby 24 hours a day 365 days of the year !!!