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Re: [HCDX] Dxers Unlimited's weekend edition for 11-12 August 2007
Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited's weekend edition for 11-12 August 2007
By Arnie Coro
radio amateur CO2KK
Hi amigos short wave listeners around the world, hi amigos radio
amateurs worldwide and in space, hi amigos TV and FM Dxers, YES, this is
the weekend edition of your favorite listener oriented and technically
minded radio hobby program, covering each and every one of the more than
81 ways you and I enjoy this wonderful hobby... I am Arnie Coro, radio
amateur CO2KK, your friend here in sunny Havana now ready to share with
each of you about 17 minutes of on the air and on the web time assigned
to this program. Here is item one: Our technical topics section will
tell you today more about modular construction, a unique way of home
brewing equipment that adds lots of fun to our hobby. Two nice modules
that are the power source of my HURRICANE ONE low power amateur
transceiver will be reviewed... Item two: From radios to antennas, as
each radio needs at least one to work... Our antenna topics section will
be devoted today to answer the questions sent in by several listeners
about the BOBTAIL and the HALF SQUARE antennas that I talked recently
about here at a previous edition of the program... Item three: More
answers to other radio hobby related questions during our numero UNO,
the super-popular YOU HAVE QUESTIONS and ARNIE TRIES TO ANSWER THEM
section of Dxers Unlimited, that today will answer questions sent in by
listeners in North America... Item four: Some notes about equinoctial DX
propagation, to refresh your memory about what we may expect in about a
month from now, as we approach the autumn equinoctial DX season, and as
always , at the end of the show, our exclusive and not copyrighted, HF
plus low band VHF propagation update and forecast...
Stanby now for a few seconds, if you happen to be listeninig with a
vintage receiver, then use the antenna trimmer to peak the signal , as
Dxers Unlimited's weekend edition continues after this short musical break
....
Si amigos, YES my friends... this is Radio Havana Cuba, the name of the
show is Dxers Unlimited, and this is a program especially designed for
those of us that enjoy the radio hobby, from newcomers that are spending
their first fascinating day with a new short wave radio, to old timers
that keep listening to short wave despite the fact that they have
enjoyed the hobby for decades..
Here is now item one: MODULAR CONSTRUCTION, and why it helps a lot to
add enjoyment to our hobby... Just a few days ago, the President of one
of the city of Havana's 14 radio clubs called me on the phone to request
help with several new radio amateurs that had just passed their ham
radio license test but had no equipment to go on the air... Coro, he
said, please help my club, we want to build several HURRICANE ONE rigs,
and would
appreciate your advice, as we know that you actually
are the person who designed it ... OK Jorge, I told him, but be prepared
to work with a different way of
building homebrew radios... We are going to GO MODULAR... !!! Then he
asked about the way the new HURACAN UNO transceiver was to be built, and
I told him that each of the modules could be assembled and tested
individually, something that helps a lot when you are involved in a
complex project like building a transceiver, even if it is a very simple
one...
Jorge, I emphasized to the Marianao Radio Club President, we will be
starting with the power supply module, well, actually with the TWO power
supply modules as the HURRICANE ONE, or HURACAN UNO in Spanish, main
purpose is to provide emergency communications capability during the
hurricane season that here in Cuba lasts for a very lengthy period
spanning from the first day of June to the last day of November !!! OK,
Coro, I agree, so let's start to work.. and so we proceeded to talk
about part one of the project, the two power supply modules, one to be
used when the AC power line could provide service, and the other one to
be used when , as they do here in Cuba routinely when the hurricane
approaches, the power company disconnects all the services in order to
reduce the wind and heavy rains caused damages, a practice that has
proven to be very effective. Our utility has developed certain
operational criteria, so that when the wind speed exceeds a certain
miles per hour figure, the power lines are simply switched off at the
sub-stations. Then amateur radio communicators must use battery power to
keep those vital links working, and the HURACAN UNO has a DC power
interface precisely to make that possible in the safest and most
reliable way.
The AC power supply provides regulated direct current
at 13.8 volts at a maximum current of 3 amperes, more than enough to
power the HURACAN rig to maximum output both on double sideband or CW,
and there is plenty of current to spare. Connecting the HURACAN UNO to a
battery is not done with just two wires coming out from the
transceiver... that has proven to be very unreliable, because in the
middle of an emergency, there are good chances for the wires to be
connected with the wrong polarity, or even to voltage source that may
exceed the 15 volts DC maximum design criteria for this transceiver.
Instead, the HURACAN is connected to a DC power source using an
interface, a little box that provides the vitally important reverse
polarity protection, and also disconnects the rig automatically if the
DC voltage source provides more than 15 volts, something that may happen
if you connect the rig to an automobile or truck electrical system and
keep the engine running... Jorge, has now all the circuit diagrams and
technical information, and he is proceeding to gather all the components
for the first group of power supply modules. Once they are finished and
fully tested, we will then continue with the MODULAR PROJECT, by
building the receiver's audio module, that includes the audio preamp,
two active filters and the output power amplifier. MODULAR CONSTRUCTION
then makes possible testing the AUDIO MODULE, powering it up from the AC
supply...As this project is targeted at beginners absolutely no attempt
is made to produce a miniature radio... enough space is left for the
newcomer to be able to learn how to solder without damaging nearby
components !!! The HURRICANE ONE PROJECT continues with the assembly of
several more modules that are then wired up together inside a rather
large sized box....Once completed, the proud owners will be able to
operate on the 40 meters amateur band , from 7000 to 7150 kiloHertz ,
running 10 Watts of
Double Side Band or 15 Watts of CW ... More than enough power to even
work some DX !!! I will keep you all up to date on how this project
continues, and yes, as many of you already could guess, we are using
mostly, about 90 percent recycled electronic components from retired
TV sets !!!
.....
From radios to antennas !!! Because, even the best
radio in the world is quite useless without a good antenna... As a good
friend of mine likes to say... For every monetary unit spent on your
radio, spend at least three to ten monetary units in your antennas and
you will certainly enjoy the hobby a lot more... Several listeners from
North America wanted to learn more about both the BOBTAIL and the HALF
SQUARE vertically polarized antennas, so I am going to try to answer at
least to the three most frequently asked questions...
Question one: Sent by Gabe in Atlanta... Gabe wants to know if he can
design a HALF SQUARE for the 70 centimeter band, because he wants to
reach to repeaters located in opposite directions.. SURE AMIGO GABRIEL,
you can certainly design and build a HALF SQUARE for the seventy
centimeters amateur band FM segment, and it won't take you much time...
My favorite building material for the HALF SQUARES above 30 megaHertz is
number 8 copper wire... as it is easy to work with and you won't loose a
lot of money in case you cut it at the wrong poing when tuning up the
system...For my 2 meters and 70 centimeters bands HALF SQUARES I use
white PVC plumbing pipe as a support, and it works very well indeed...
Do keep in mind that the HALF SQUARE produces a horizontal radiation
pattern that looks like a peanut... it is not exactly like the dipole...
and by the way, you would see a gain of no less than 4 decibels above a
dipole using a HALF SQUARE that will cost you next to nothing to
homebrew amigo Gabe...QUESTION NUMBER TWO:Arnie , can I place a
reflector curtain behind my already built HALF SQUARE ? I do want to
reach two distant repeaters , but both are in the same general
direction... thanks for providing us with Dxers Unlimited twice weekly,
signed Jerry in Chicago... Well amigo Jerry, thank you for the kind
words, and let me tell you that SURE, you can add a passive reflector at
a quarter wavelength behind your already built 70 centimeter band half
square, and that will turn the antenna into a unidirectional system...
and will add quite some gain to it too... Build a panel roughly 80 by 80
centimeters , and place wires every
2 centimeters ... so you will need quite some wire to make your passive
reflector... I have used enamelled copper wire from burned out
transformers to make those reflector screens at almost no cost...Then
place the already built half square at a distance of about one quarter
wavelength at the center operating frequency you are planning to use ...
for the 440 to 450 megaHertz repeater sub-band this is about 17
centimeters from the radiating vertical elements to the screen... You
can optimize the standing wave ratio seen on the feedline by just moving
the antenna back and forth from the screen and watching how the SWR
meter's needle moves up and down !!!
......
Now amigos , here is our numero uno, the MOST POPULAR section of the
program, YOU HAVE QUESTIONS and ARNIE TRIES TO ANSWER THEM ... here at
Dxers Unlimited's weekend edition. You can send your questions to
arnie@xxxxxx, again, arnie@xxxxxx, and also VIA AIR MAIL to Arnie Coro,
Radio Havana Cuba, Havana, Cuba.
Today's question sent in by a newcomer to the hobby. Maggie in
Southhampton , England, wants to know how it was possible for her to
pick up Radio Havana Cuba's Caribbean English language broadcast at her
location.. Well amiga Maggie, that's part of the magic of radio... our
11760 kiloHertz transmitter is using an antenna that is omnidirectional
so that’s why you were able to pick it up there last week... Normally
international short wave broadcast stations beam signals to a certain
target area using highly directional antenna systems, but even those
antennas have sidelobes that disperse minute amounts of energy that can
travel great distances when propagation conditions are good !!! So amiga
Maggie, now you know why were you able to pick up us on 11760 khz during
your local evening there in England !!!
....
And now amigos, here is as always at the end of the show, our exclusive
and not copyrighted HF propagation plus low band VHF propagation update
and forecast … Solar activity continues at very low levels, with the
daily solar flux barely reaching 70 units…The effective sunspot number
Saturday at 13 hours UTC was at the rock bottom figure of 6, indicating
very low solar activity and experts believe that we have already reached
the bottom of the solar cycle by now, as the most recent forecasts call
for a smoothed sunspot number of about 20 by December of 2007, something
that is very good news to all users of the short wave spectrum. Send
your signal reports and comments about the program via e-mail to
arnie@xxxxxx <mailto:arnie@xxxxxx> and VIA AIR MAIL to Arnie Coro, Radio
Havana Cuba, Havana, Cuba
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