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Re: [HCDX] Dxers Unlimited's mid week edition for 21-22 August 2007
Radio Habana Cuba
Dxers Unlimited
Dxers Unlimited's mid week for 21 -22 August 2007
By Arnie Coro
radio amateur CO2KK
Hi amigos radioaficionados !!! This is the mid week edition of your
favorite radio hobby program, still not too good short wave propagation
conditions due to the effects of the prevailing very low solar activity
More about HF and low band VHF propagation conditions at the end of the
program...
Item two: A nicely built radio, powered by radio waves, was recently
shown to me by a Cuban radio amateur... The set uses high efficiency
tuned circuits connected to an external antenna... This receiver has two
tuning dials... one for selecting the frequency of the station that you
want to listen to, and the other selects the frequency of the station
that provides power to the radio.... Amazing isn't it!!! And let me tell
you that the radio powered radio works nicely; especially if you are
located not too far away from a powerful AM broadcast station. Now my
friend is experimenting with a somewhat different circuit, as he is
exploring the use of the local low VHF band TV channels to supply power
to his receiver. His battery less radio works as long as the station
supplying the power is on the air, and was designed and built to show
his teenager son that a radio amplify signals by obtaining power from
the air!!!
For those of you that are technically minded, Carlos my friend used a
pair of high gain germanium transistors for the audio amplifier of the
crystal set, and he optimized the tuned circuits of both tuners so as to
obtain maximum efficiency, so this radio is not a miniature set at all!!!
Item three, as expected the past several weeks of the summer season we
have had to deal with much lower maximum useable frequencies than those
prevailing during 2006... Among the highlights of my monitoring of the
HF bands was the fact that the 10 meters band was open for several
hours, but in a much different way than during the peak of this solar
cycle...
10 meters was open to very specific areas for a certain time, almost
always by means of Sporadic E layer events, and on very few occasions F2
layer opening happened briefly.
More radio hobby related information coming to you in just a few
seconds, as Dxers Unlimited's mid week edition continues...
I am Arnie Coro in Havana...
.....
This is Radio Havana Cuba, the name of the show is Dxers Unlimited, and
if you are a first time listener, let me tell you that our station has
just issued a new very nice
looking QSL card to verify reception reports... you can send your signal
reports and comments about this and other RHC programs via e-mail
directly to me; send mail to arnie@xxxxxx, again arnie@xxxxxx and if you
don't have an e-mail account, then send me an AIR MAIL postcard to:
Arnie Coro, Radio Havana Cuba, Havana, Cuba, but don't forget both in
the e-mail or postcards to include your return address...
Now here is item four of our midweek edition, its la NUMERO UNO, and the
most
popular section of Dxers Unlimited... YOU HAVE QUESTIONS, and yours
truly Arnie Coro tries to answer them... Here is today's question, sent
in by listeners in the USA, Canada, Germany and New Zealand... They, all
eleven of them wanted to know more about equinoctial propagation...as in
just about two weeks from now we will be enjoying the autumn equinox
propagation season...Why experienced short wave listeners, tropical
band enthusiasts, AM broadcast band Dxers and radio amateurs set aside
as much operating time as possible during the year's two equinoctial
periods..?
Answer: Well amigos, the fact is that starting around the first week of
Septemberh and lasting until the second and sometimes the third week of
October, radio propagation conditions get better at a worldwide scale...
As a matter of fact they become so good, that many radio amateur
contests are organized so that they take place precisely during the so
called autumn equinox... Likewise, starting around the second week of
March and lasting until mid April, the spring equinox boosts propagation
conditions in a somewhat similar but not exactly the same way, because
during September and October the height of the ionosphere's F2 layer
during the daytime and the F layer during the evenings is lower, and its
free electron concentration is higher, so for all practical purposes the
autumn equinox DX season is always much better for Dxing than the spring
season....
So in order to answer listener's Ted from New Zealand question, yes
amigo, it's true, the autumn equinox of the northern hemisphere, that
happens during the period from more or less mid September to mid
October, brings radio hobbyists above the Equator better propagation
conditions than the spring equinox !!! Also, I must add that the March
equinox is usually associated with recurrent solar disturbances that
provide some very interesting effects too...
Question number two: It came from listener Rubin, in the UK... he wants
to know if he can connect a power amplifier to a small 5 Watt amateur
radio transceiver that he bought recently...He says in his letter, Arnie
I just bought a YAESU FT817 ND, the new version of that radio that has a
much better designed RF power amplifier module... and I want to know
what kind of RF amplifier I can connect to this equipment. Well amigo
Rubin, the FT 817 ND provides typically a 5 Watts output level, so in
order to be effective the amplifier should be capable of 10 dB gain to
provide a 50 Watts output level, 13 DB gain if you want to boost your
power to 100 Watts, and 20 dB gain if you want to increase your station
power output to 500 Watts... a 23dB gain level will boost your power to
one kilowatt...
Be aware that in actual practice your amplifier must provide a little
more gain, so as to compensate for losses ...and don't forget that the
RF power amplifier will need a heavy duty power supply to handle the
high current required by a solid state final
stage.
Connecting the FT817ND transceiver to the RF power amplifier requires
the use of a short length of double shielded coaxial cable, and my
advise is to add a copper strap ribbon as a common ground connection
between the FT817ND and
the power amplifier's cabinet and chassis....Amigo Rubin, I do want to
emphasize
the importance of making this connections properly, and I must
highlighted also the need to connect the transceiver, the linear
amplifier, their respective power supplies and the antenna tuner all
together to a proper ground system. Many of the problems associated with
the use of high power linear amplifiers are derived from poor
installations that lead to instability, overheating and the generation
of interference to other radio services. As a matter of fact, my opinion
is that one should keep the use of amateur radio stations to the least
power possible to achieve good results, which for all practical purposes
very rarely requires using more than one hundred Watts...
QRP, or low power operation is a wonderful way to test your operating
skills and the new digital keyboard to keyboard communications modes
like PSK31, MFSK16 , MT63 and Olivia are ideal for operating a ham radio
station with minimum power and still achieving very nice two way contacts!!!
......
How many people around the world listen to short wave broadcasts ?
That's a question that needs to be addressed constantly, because, this
topic is leading to many different answers... While it is quite certain
that listening to short wave radio broadcast programs has seen a steady
decline in developed nations, there are several hundred million people
around the planet that listen regularly from their less developed
countries , and there are very good evidences that in highly developed
areas of the world, short wave listening is crisis related, with peak
audiences happening at the start of any international critical
situation. Let me add that accurate, really reliable audience research
is very hard to achieve with short wave listening, so estimates vary
wildly and some of those estimates have, in my opinion ,have misled some
station managers into taking unwise decisions, like the complete
shutdown of transmissions. The availability of relatively low cost short
wave radios using present day digital technology has simplified tuning
of the wanted frequencies, so today's listeners are in a much better
situation than those 20 or 30 years ago that had to rely upon poorly
calibrated analog dials... Another issue that I believe must be dealt
with is what could best be described as "listeners training", because
short wave radio does require certain skills in order to achieve
reliable results... My perception is that as better receivers become
available and people learn how to install better antennas, the
improvement in reception will keep those already listening regularly
highly motivated... Last but not least... international short wave
broadcast stations that are really interested in providing their
audience with high quality programming and information about their
nation, should keep in mind that creating and maintaining both an
audience research unit and a fully staffed attention to the listeners
department are essential to learn about what the audience wants, when
and where the station is heard and summarizing how effective the work of
the station really is.
Yet another interesting aspect that has now become part of practically
all international broadcast stations is the availability of an INTERNET
website where listeners that have computers and connectivity can go and
obtain both daily news and in most cases also audio, either by direct
streaming feeds or by means of audio on demand that can be downloaded at
will. But, again, I want to underscore that INTERNET services , although
available now to almost one billion people around the world, are still
limited to the existence of electrical power, computers and connectivity
to link into the INTERNET, something that everyone knows is not
universally available ... May I request your opinion about this topic by
means of answering a question... Here is the question: DO you think that
international short wave broadcasting is important for today's world?
Please send your replies to the question... to arnie@xxxxxx, or VIA AIR
MAIL to Arnie Coro, Radio Havana Cuba, and Havana, Cuba...
....
And now, as always at the end of the program, here is our exclusive and
not copyrighted HF plus low band VHF propagation forecast amigos...
Solar activity is very low, and will continue at very low to low levels
during the next several days. For six consecutive days the daily sunspot
count has been ZERO, but that may change as at least one and possibly
two active sunspot regions are about to enter the visible solar disk.
Solar flux has also been correspondingly low at between 68 and 70 units,
the baseline level for that solar parameter. The effective sunspot
number for feeding into your computer propagation forecasting software
is around 8, and don't expect daytime maximum useable frequencies higher
than about 20 megaHertz at peak time. See you all at the weekend edition
of the program, that will be on the air on Saturday and Sunday UTC days.
Don't forget to send me your signal reports and comments about the
program to arnie@xxxxxx or VIA AIR MAIL to Arnie Coro, Radio Havana
Cuba, and Havana, Cuba...
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