Hi amigos radioaficionados !
Welcome to the weekend edition of Dxers Unlimited, coming to you from Havana.... propagation
conditions are going to take a turn for the worst once again,according to scientists a solar
filament is going to produce yet another geomagnetic disturbance starting on Monday UTC ... As we
continue to move well into the autoumn equinoctial DX season , this weekend will perhaps be one of
the the bests so far after the terrible summer season of 2003 , one of the worst that I can remember
since cycle 19, the first solar cycle that I had the opportunity to enjoy, when my first

Amateur radio station went on the air way back in 1957 ¡ Item two: high speed digital radio
communications are possible now using faster modes like the PSK63, a ham radio operator's dream for
keyboard to keyboard contacts... The interface for the PSK63 mode is very easy to implement, as a
matter of fact, it is exactly the same as the one used for the extremely popular PSK31 mode that is
now the favorite digital mode among the world's amateur radio enthusiasts... Item three: Planet
Jupiter's powerful radio transmitters will be heard much better soon, when the conditions for
reception of the 18 to 44 megaHertz signals from the solar system's largest planet will be optimum ,
and that's going to happen in October, just a few weeks from now... Item four: Answering a group of
questions from Dxers Unlimited's fan Bruce Atchinson ..He wanted to know more about cordless phones
to write an article about them... and I am sure that amigo Bruce was very happy with all the
information I sent him via e-mail so that he could provide his readers with an up to date account
about cordless phones and how far they can be heard ¡!! Item five: More questions answered during
the week, to listeners sending them to arnie@rhc.cu, included details about the short version of the
multi band fan antenna, a still more compact version capable of operating from 14 to 30 megahertz
that has proven to provide excellent DX performance, and also a question that came in from a
listener here in Cuba, yes, English is Cuba's most popular second language and lots of Cubans enjoy
listening to Radio Havana Cuba's English language programing , including Dxers Unlimited. The
question sent in by a listener in Cienfuegos dealt with the design of a DC power supply and it was
quickly answered via e-mail too... So amigo Lazaro in Cienfuegos has now his regulated 9 volts DC
supply providing power to his short wave radio ¡!!

Item six: the antenna topics section.... and as always at the end of the show

Arnie Coro's Dxers Unlimited's HF plus low band VHF propagation update and forecast. Margarita
Delgado is my sound engineer , now please stay tune for more radio hobby related information coming
to you from Havana ¡

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Si amigos, yes my friends, this is Dxers Unlimited's weekend edition and here is item seven of today
's program, the antenna topics sections... Today a bit more about magnetic loops, and how they can
provide extremely effective performance even on the lower frequencies , if you follow my advice...
Magnetic loops designed to operate from about 14 to 30 megaHertz can be made rather small, with a
diameter of around 1 meter or 3 feet you can really enjoy operating on the 20, 17, 15, 12 and 10
meter bands.... YES, a very small compact antenna, just one meter in diameter will give you 5
amateur band coverage , and you can also pick up stations all in between... BUT, attempting to use
compact magnetic loops on frequencies below 14 megaHertz usually ends up in total failure... Want to
know why ¿ ¿ Well very simple... they are usually made too small, and they are made using small
diameter copper or aluminum tubing for the antenna element itself, add to that the use of low Q and
high loss capacitors and you will end up with a poorly performing magnetic loop... Now listen to
your amigo Arnie Coro's advice: Make your low frequency bands magnetic loop the right way and the
performance will improve dramatically... For example a three meters or 10 feet diameter magnetic
loop made using two inch or 50 millimeter copper pipe for the antenna element, and tuned with a
homebrew low loss butterfly type variable capacitor will match the performance of a full size 40
meter dipole to such an extent as to leave everyone involved in the comparison test totally
amazed... Sure, a three meter magnetic loop made with 50 millimeter tubing is an impressive antenna,
but you will agree with me that it can fit where a full size half wave dipole for the 40 meter band
won't. As a matter of fact the 3 meter diameter loop will also provide super performance on the 30,
20 and 17 meter bands too... and somewhat reduced performance on both the 80 meters and the new 60
meters bands ¡!! Building such a large sized magnetic loop is something that must be done with
extreme care because of the mechanical problems involved, but as I told recently to a Dxers
Unlimited listeners that wrote to arnie@rhc.cu, the 3 meters diameter loop was in my opinion the
only option he had at his particular location... About a month later I received a nice e-mail
message, in which Augusto my Italian listener was telling me about the succesful construction and
excellent results obtained with the large loop, that is now permanently installed at his ham radio
station and listening post. Augusto used a very well built remote control system to move the
butterfly variable capacitor from his operating position.... and he also told me that he could tune
the antenna from 3 megaHertz all the way up to 15 megaHertz, giving the antenna an excellent five to
one tuning range. Augusto also explains that on the 40 meter band he could compare the 3 meter
diameter loop made with 2 inch or 50 millimeter copper pipe with a standard half wave dipole, and
that he was amazed by the outstanding results that the magnetic loop provided at some specific
distances.... Another of his comments dealt with the loop's ability to reduce the local noise ,
something he achieved by turning the loop to minimize the noise picked up from his neighbor's
computer, that according to Augusto is a real trouble maker for his short wave radios ¡!!..

If you want to learn more about magnetic loop antennas, just drop me an e-mail to arnie@rhc.cu and I
will be more than happy to send you several computer files with plenty of things to read about these
very interesting antennas ¡!!

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This is Radio Havana Cuba, the name of the show is Dxers Unlimited, and yes amigos, our show
attempts to cover the more than 70 ways you and I enjoy this wonderful hobby ... RADIO... Here is an
unsual aspect of our hobby that is seldom heard about... are you aware that there are radio amateurs
that just refuse to operate with modern up to date equipment, and spend all the time on the air
using vintage communications gear... I have a good friend in Iowa , USA, that will never be on the
air with equipment built after the Second World War, and amigo Ken has built the most beautiful
working reproductions of radio equipment that he has copied from Handbooks between 1925 and 1940
.... He even has asked a friend of his that is a ceramics expert to make for him the special ceramic
ribbed insulators so popular among radio fans during those early years of radio... Building or
reviving antique radio equipment is one of the many ways to enjoy the hobby, and more and more
people are becoming interested in this aspect of our wonderful way of enjoying our spare time ¡!!
Item nine: Another not so frequently heard way of enjoying the radio hobby: model airplane radio
control flying... Yes, it combines two hobbies, and believe me that it's thrilling... I happen to
have a very good friend that lives not too far away from my home, who is a full time radio control
airplane fan... Manolo has built the most elaborate digital radio control systems, and he uses them
on the 52 to 53 megaHertz segment of the 6 meter band to avoid possible interference that may
disrupt the flight of his beautiful model aircraft... For operating the radio control equipment
within an amateur radio band you will certainly need an amateur radio license amigos, but with the
most recent changes regarding the requirements to obtain a ham radio license, it's now becoming
easier than ever to be on the air with your own amateur radio station. So if you enjoy model
airplane flying, or maybe like to race model sailboats, think about how much added fun can be had by
using modern digital fail-safe radio control systems ........




Not much time left today... but before we go QRT here , there are few more bits of information to
make available... one is related to questions about the substitution of early days vacuum tubes and
transistors required to repair equipment... I will certainly continue to handle those requests on a
case by case basis, until those who ask are able to bring the equipment back to full operating
parameters... The most recent case was a short wave listener that was re-building a very nice
COLLINS 75 A 1 receiver, and he couldn't find a replacement for the 6SJ7 audio pre-amplifier
stage... in order to make the nice radio come back to life, I advised him to use an adapter built
from a 7 pin miniauture tube socket and a discarded 8 pin tube, so that a 6AU6 miniature 7 pin tube
could be used to replace the 6SJ7... The practical solution worked very well, and nothing had to be
changed on the radio, so that when an original 6SJ7 is found , amigo Andy can just plug it in... As
you may realice Andy is very happy , as he is listening on his 75 A 1 1948 vintage receiver right
now, while he still searches for the elusive 6SJ7 metal tube ¡!! And now amigos as always at the end
of the show here is Arnie Coro's HF plus low band VHF propagation update and forecast... Good
weekend for Dxing on HF, but things may take a turn for the worst on Monday and Tuesday as yet
another geomagnetic disturbance is expected... Solar flux and solar sunspot counts are at a low ebb,
and the daily MUF, the maximum useable frequency curve is now much lower than a year ago at this
time... Expect nice DX on the 30 and 20 meter amateur bands, and easy listening on the 25, 22 and 19
meters international short wave bands ¡!! See you all at the mid week edition of the program and don
't forget to send your signal reports and comments about the program to arnie@rhc.cu