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Re: [HCDX] Dxers Unlimited's weekend edition for 1-2 September 2007
Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited’s weekend edition 1-2 September 2007
By Arnie Coro
Radio amateur CO2KK
Hi amigos radioaficionados… I am Arnie Coro , radio amateur CO2KK in
Havana, inviting you to stay here on this frequency or world wide web
connection listening to Dxers Unlimited’s weekend edition… Well, here we
are, now right at the start of the autumn equinoctial DX propagation
season, as I like to properly call it… Because there is no doubt that no
matter how the solar cycle is behaving as the autumn equinox approaches
short wave propagation conditions around the world improve dramatically
for a period that usually lasts from four to six weeks… starting just
now, when during the first week of September one starts to notice how
the HF bands begin to improve…
For example 20 meters, the queen of radio amateur DX bands will be open
to one part of the world or another for many more hours every day…
Wednesday afternoon I heard a very loud signal on 20 meters single side
band coming from the United Kingdom into the Caribbean… The UK station
was benefitting from the typical local sunset propagation enhancement,
and he was an S 9 plus 10 dB on peaks perfect copy on my 20 meters band
half wave dipole “slopper” antenna, that is tilted at a 45 degrees angle
with the lower end aiming at Europe, to make one of the lowest cost
“beam antennas” that you can imagine…
So amigos, follow your friend’s Arnie Coro advice and devote more time,
from now on to operating your radios, because propagation conditions
will continue to get better and better for the next three to five weeks…
Stay tuned because after a short break for station ID, Dxers Unlimited’s
weekend edition will continue in afew seconds… I am Arnie Coro in Havana…
…….
The name of the station is Radio Havana Cuba, we have been on the air
since 1961, and we are proud of providing our listeners with one of the
world’s best QSL services… Yes , we do verify reception reports with a
nice , beautiful QSL CARD… a collectors item by all standards amigos…
Send your signal reports, comments about our programs and radio hobby
related questions to arnie@xxxxxx or VIA AIR MAIL to Arnie Coro, Radio
Havana Cuba, Havana, Cuba…
And now here is item two, also HF propagation related… Tropical Bands
propagation also benefits from the autumn equinox season, and this is
your opportunity of logging some nice catches on the 60 meters Tropical
Broadcast Band, the one that still has a relatively large number of
stations on the air… Let’s start with our own Radio Rebelde, from Havana
operating 24 hours a day on 5025 kiloHertz for our domestic near
vertical incidence skywave coverage of the Cuban archipelago, something
that the Tropical band is able to do with just one transmitter and a
special NVIS antenna system… But, the NVIS antennas also have minor
lower take off angle lobes that send the signals at much longer
distances, and that’s why you can pick up Tropical Band domestic
services from across the globe… Here are a few stations from Africa that
may be logged in North America and Europe during the present autumn
equinoctal DX season… Starting with ANGOLA.on 4950 , from Mulenvos, but
beware that this transmitter is usually with very low modulation index..
From the Republic of Benin, on almost exactly the same frequency as
Radio Rebelde on 5025 kiloHerts is Radio Parakou, that you may catch
when late in the evening daylight saving time, around 0500 UTC Radio
Rebelde’s 50 kiloWatt transmitter on 5025 kiloHertz is off the air for
routine maintenance…something that happens about once a month… at other
times picking up Benin of 5025 kiloHertz is a matter of luck, when
propagation changes in favor of the African station over the Cuban on
the same channel.
Moving just 5 kiloHertz up the 60 meters Tropical Band from 5025 to 5030
kiloHertz you may sometimes pick up BURKINA FASO,’s Radio Burkina from
the capital of that African nation Ougadougou, again when a the station
from Costa Rica on the same frequency is not on the air, or propagation
at your location favors the African continent..
These are just four examples of Tropical Band stations that you add to
your logbook during the present equinoctial DX season amigos, but there
are many, many others that make very interesting listening ,especially
for the nice music they play that you will very rarely if ever hear at
your local FM one hundred thousand watts stereo powerhouse !!!
….
Now amigos, here is our technical topics section, that will be devoted
today about the growing interest among radio amateurs to use AM
modulation, and by that I mean standard double side band plus full
carrier AM, the first way of superimposing voice and music on a radio
carrier wave… A few days ago during a 40 meters bandscan that I was
doing late at night with my REGENERODYNE homebrew receiver set for
picking up CW and Single Side Band station, a loud signal produced a
really loud heterodyne… backing off the regeneration control, the AM
signal came in with excellent audio quality. It was a radio amateur from
Ohio, USA, operating a vintage transmitter that he described as more
than 50 years old. The four dash four hundred tetrode final , modulated
by a pair of eight thirteen tetrodes was certainly providing excellent
reception. The proud owner of the AM rig was using a simple half wave
dipole , so his actual antenna gain was zero db or decibels over a dipole.
He told the stations he was talking to that he was using a 1950’s
vintage Viking One transmitter at a very low power setting to drive the
big tetrode that was fed with three thousand volts on the anode… The
classic class B modulator with the eight thirteen tetrodes provided all
the audio needed for one hundred percent modulation and more, something
that as he properly explained is very important if you want your AM
signal to provide the highest possible quality sound with very low
distortion… But this Ohio ham operator was not the only one I have heard
recently, because as I just said more and more radio amateurs are coming
back to AM to enjoy the beautiful audio quality that is possible using
that form of modulation, while at the same time keeping on the air some
nice antique equipment…. I have heard recently AM amateur stations also
on 20, 15 and 10 meters, and the hams operating those stations seem to
enjoy it a lot, as they are not chasing DX or working one station after
the other in contest… they are just relaxing , talking to each other and
discussing some very interesting technical topics, like the design and
construction of amateur radio transmitters that use amplitude modulation
techniques, not only the classical ones everybody knows about, but some
of the more advanced pulse width modulation technology that has become
almost a defacto standard for AM broadcast stations but that has seen so
far very little if any use among the world’s radio amateurs.
……
You are listening to the weekend edition of Dxers Unlimited coming to
you from Havana, and here is now LA NUMERO UNO, the number one most
popular section of the show…
YOU have questions and your amigo Arnie tries to answer them… Here is
today’s question sent by listener Gabriel from Atlanta, Georgia , USA…
Gabe, as he signs his e-mail, wants to know more about regenerative
receivers and why they seem to have such a devoted group of people
around the world always experimenting with those circuits that , he very
well describes them, do require a lot of attention to construction
details in order to achieve good performance… Well amigo Gabe, it may be
a matter of accepting a challenge, or the pride to be listening to a
relatively simple radio that you have built yourself, and that picks up
distant stations better than your store bought radio… Maybe those are
the main reasons that make radio hobby enthusiasts enjoy so much
discussing the circuits with friends at the e-mail lists devoted to
regenerative receivers, changing parts values to see how the performance
of the radios change, or experiment with rarely known circuits used in
the very early days of radio and long forgotten, like the so called
“space charge tetrodes ”, that became popular because it made possible
to build a radio receiver that used only one single 6 , 9 or 12 volts
battery…. And this of course was happening when radios were battery
operated and required expensive so called B PLUS B+ batteries for
providing the high voltage to the vacuum tubes anodes… Just for your
information amigo Gabe, I have sent to you already , via e-mail the
circuit diagram and my notes of a regenerative receiver that uses low
voltage for feeding the anodes or plates of the vacuum tubes, in other
words, it doesn’t require the use of a high voltage power suppy, because
both the tubes filaments and anodes are fed from the same 12 volts DC
power supply… Maybe you can homebrew this receiver diagram that has
given many radio enthusiasts many hours of nice AM broadcast band and
shortwave listening…
Please note amigo Gabe that the vacuum tubes types used are not critical
at all, so you won’t need to spend a lot of money buying specific tube
types that are much sought by HI FI audio hobbysts who are erroneously
led to believe that certain tube types have some magical qualities that
make their audio sound better than others… My prototype of this cascode
regenerative 12 volts operated set was built and is still operating
using vacuum tubes recycled from TV sets that were retired from service…
I never even tested those tubes , just plugged them in, and the radio
started to provide excellent reception , so I just left them there amigo !!!
Now for those of you wanting to learn more about regenerative receiver
circuits, both vacuum tubes and solid state, just send me an e-mail to
arnie@xxxxxx, and I will send you a few circuit diagrams plus the
address of one of the most popular regenerative receivers discussion
forums on the Internet, that I strongly recommend you to join, as it is
a treasure chest of knowledge that its members share with each other in
a most civilized and educated way, with a spirit to share what each one
knows that is an excellent example of how the Internet can be used for
the promotion and development of the radio hobby …
And now as always at the end of the show, here is Arnie Coro’s Dxers
Unlimited, HF plus low band VHF propagation update and forecast.. Solar
flux still at very low levels and a new sunspot group is growing, but it
would not produce big solar flares according to what can be seen. The
equinoctial propagation conditions are now very much in progress , so if
the flux increases above 80 units we are going to see much better
propagation by mid September… See you all at the mid week edition of
Dxers Unlimited, next Tuesday and Wednesday UTC days amigos !!!
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