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Re: [HCDX] Dxers Unlimited´s weekend edition for 9-10 August 2008
Dxers Unlimited
Dxers Unlimited's weekend edition for : Saturday 9 and Sunday 10 August 2008
By Arnie Coro
Radio amateur CO2KK
Hi amigos radioaficionados the world over ! Yes my friends !!! Your
receiver is now tuned to the short wave frequency where you are just
starting to listen to the weekend edition of Dxers Unlimited, the radio
hobby program that provides you with the most up to date, accurate, and
reliable short wave propagation updates and forecasts...
Item one,short wave propagation continues to be really very poor and
actually even worse than during the past few days, because a high speed
solar wind coming from a coronal hole is affecting our planet … and of
course we are still having to deal with the effects of the many days
with a zero sunspots count.
Sporadic E layer openings will now, during the second half of August ,
slowly diminish both in frequency and duration , but each and every
time,when the bands above 25 megaHertz open due to the presence of a
Sporadic E layer high density cloud, amateurs operating on the 12, 10
and 6 meter bands will have a wonderful opportunity of working nice DX
and the same holds for TV and FM broadcast band Dxers .
The 12 and 10 Meters bands have provided E skip openings that continued
to occur even very late in the evening local time, and as it often
happens with E skip, signals reflected by the E layer clouds at
altitudes of between 90 and 120 kilometers above the Earth´s surface
suffer from deep fades, and sudden enhancements, and they seem always to
appear and vannish misteriously without scientists having had the clues
yet of what is really causing those openings……Hams that operate on the
50 megaHertz or 6 meters band radio amateurs are also enjoying what may
be the last openings of the summer E skip season…
Now let me repeat, once again this propagation related news item, if you
happen to notice poor reception on frequencies from 10 to 30 megaHertz
during your local daylight hours via F2 propagation , it is certainly a
consequence of the effects of the extremely low solar activity that has
lasted for so many days now ...Again the solar flux average for the
month of July was amazingly low… so low in fact that, I repeat it again,
solar scientists are practically sure that the solar cycle is going now
trough a second minimum…
Stay tuned… I will be back in just a few seconds with more radio hobby
related information after a break for station ID. I am Arnie Coro, radio
amateur CO2KK in Havana
……..
You are listening to Radio Havana Cuba, the name of the show is Dxers
Unlimited and here is now
Item two: The technical topics section of the program. Today I will be
telling you more about the ultra simple ham radio equipment that some
radio hobby enthusiasts are building and operating with quite succesful
results.
One example is the interest generated around the so called PARASET, a
World War II very simple transmitter-receiver built by the British for
providing behind the enemy line clandestine radio operators with a
compact unit.
During World War II the only active electronic devices were vacuum
tubes, so the designers of the PARASET had no other choice but to use
them. The rig consists of a tetrode vacuum tube operating as a crystal
controlled oscillator and capable of putting out no more than 5 Watts of
radio frequency power… so, by definition it is a QRP or low power
transmitter.
The receiver used two pentode tubes, or valves, as the British call
them, one acting as a regenerative detector and the other one as a high
gain audio amplifier. In actual practice, the PARASET operators ran a
very high risk, because their regenerative receiver generated a signal
that was radiated by the antenna… so they , so to speak, were on the air
all the time the PARASET was in operation, something that the very well
trained German Army Radio Direction Finding Units learned and used to
locate the PARASET operating position.
One great disadvantage of the PARASET receiver, only second to the fact
that it radiated a signal into the antenna all the time, was that tuning
was very difficult due to the lack of a properly designed bandspread
mechanism. The variable capacitor that tunes the regenerative receiver
has no vernier reduction drive, and there is no second bandspread dial,
so finding the station that was the other end of the communications link
should had been quite a challenging task for the operators of those war
time sets.
Anyway, more than 65 years after the first PARASET transmitter-receiver
boxes were dropped over continental Europe for the first time, those
radios have won the attention of many hobbysts, splitting them in two
opposite thinking teams…
One team advocates building and operating exact replicas of the PARASET,
organizing contests for them, and participating in QRP or low power
amateur radio contests using the PARASET.
The other team advocates modifying the original PARASET so as to make it
much more user friendly, by , for example adding bandspread for the
receiver, a tone oscillator to act as a keying monitor, and improve the
receiver with a radio frequency amplifier and a second audio vacuum
tube, so , as the classic PARASET operators say, that´s no longer a
PARASET, but a much modified vacuum tube QRP rig.
Well, after all, both groups are enjoying homebrewing equipment, and
also operating the newly built replicas or near replicas, that I can
tell you are in both cases quite amazing radios. Not too long ago, I
assembled an almost exact replica of the PARASET transmitter section,
operated with it on 40 meters and made quite a few CW contacts by
sending CQ DX very near to 7006 kiloHertz, a frequency that is
considered to be usually occupied by really proefficient CW DX operators…
The purpose of the experiment with the 6V6 vacuum tube power oscillator
was to show it to my ham radio training program students, that by the
way, succesfully passed the amateur radio operators test and will soon
be on the air.
Our radio hobby is certainly lot of fun, and even with a very limited
budget you can go on the air by homebrewing simple equipment, like a
replica of a PARASET !!!
Homebrewing and testing ancient radios replicas , are two of the more
than 84 ways that you and I enjoy this wonderful hobby, yours and mine…
RADIO !!!.
………
In a recent edition of Dxers Unlimited I asked the following question…
Are you ready to improve the performance of your short wave radio
receiver ?
And I also added that, it could be done, and at rather low cost, with
amazingly effective results… So here is yet another example, an actual
practical example of how to improve a low cost short wave receiver´s
performance.
You can homebrew an antenna tuner and signal attenuator, all in one box,
and enjoy the dramatic improvement in reception quality that your newly
built accesory will provide.
The results in many cases will prove to be simply amazing.
A low cost portable short wave receiver of the present generation
usually lacks adequate front end selectivity… and that is precisely what
you add ahead of the radio, by connecting your antenna tuner and signal
attenuator between the antenna and the receiver.
Your radio will now have three additional controls… The signal
attenuator at the antenna input, and two tuning capacitors, one at the
input and the other one at the output of the PI network antenna tuner.
You can use a simple carbon track potentiometer for the signal
attenuator, or go ahead and build a more sophisticated step by step
attenuator that may even be calibrated in a combination of 3 dB and 10
dB steps…
Even rather expensive up to date digital receivers have benefitted from
my signal attenuator and PI network antenna tuner box… The reason why it
works so well is that my PI network tuner tunes very sharply, in
contrast with the present day designers cost saving radio frequency
input circuits that provide a bandpass feature…
Let me explain in some detail. A modern solid state receiver or amateur
bands transceiver no longer has an antenna peaking trimmer control,
because the input circuit that connects the antenna to the radio
frequency amplifier stage of the receiver is untuned… actually it is
designed to pass a certain band of frequencies with little attenuation…
For example, when you select the seven megaHertz or 40 meters band on an
amateur radio transceiver, the set switches in, using a pair of relays,
a bandpass filter that has a tuning range from , for example 6 to 8
megaHertz, leaving the front end unprotected from the presence of
megapower international shortwave broadcasters operating above sevent
thousand two hundred kiloHertz… By connecting Arnie Coro´s signal
attenuator and PI network antenna tuner box, between the antenna and the
radio, your receiver will only ¨¨see ´´ a very small bandwidth around
the center frequency that you are operating, and that leads to much
better reception that what can be achieved with the wide band input
filter that the designers included as a cost saving measure !!!
……………….
Now here here it is , once again your favorite, LA NUMERO UNO. Our very
popular YOU have Questions and Arnie tries to answer them, a fast tract
way of solving your radio hobby related problems... Remember to send
your questions to inforhc at enet dot cu, and also via e-mail to Arnie
Coro, Radio Havana Cuba, Havana, Cuba.
Listeners from South Africa, India, Malaysia, Canada and Brazil have
ASKED ARNIE about when it is expected that the Sun will have sunspots
again… As they are all concerned by reading that the daily sunspot count
for the month of July showed that it went practically without a single
really significant sunspot seen on the solar disk. Listen carefully to
the following information:
Provisional International monthly mean Sunspot Number for
July 2008 : 0.5 (zero point five)
Yes you heard it right, the mean Sunspot Number for July 2008 was LESS
THAN ONE, a clear indication, in my opinion of a second solar cycle 23
minimum , with just two days, on the 18^th and 20^th of July when a very
small sunspot was seen by optical observers.
Well amigos, it is quite a challenge to be able to produce a solar
activity forecast at this moment. Some experts are now emphasizing that
the extended period of solar ultra quiet conditions will lead to a slow
start for cycle 24, something that is already proven to be quiet right.
The solar GURUS, also affirm that a prolonged , extended, solar minimum
has previously been associated with smaller solar activity at the peak
of the following sunspot cycle, but that will take some time to be
verified… If we see a solar peak below 100 average montly sunspot count,
then those gurus were right, but a solar peak sunspot count of 120 or
higher will not provide enough statistically significant information so
that it can be affirmed that cycle 24´s smaller peak was associated with
the previous extended solar minimum…
My own estimate is that we won´t see a significant increase in solar
activity, one that will really improve HF propagation conditions above
20 megaHertz, until the second half of 2009, and even later !!!
So, as I have said here many times since 2005, you should install the
best possible antennas for operating on frequencies between 3 and 15
megaHertz, with special emphasis on the frequency range between 3 and 10
megaHertz .
………………………
Amigos, you are listening to Radio Havana Cuba, the name of the show is
Dxers Unlimited, its on the air twice weekly and we are also providing
the scripts for you to read at my blog, dxersunlimited at blogspot dot
com... I would like to invite you to join me also on Saturdays and
Sundays for the weekend program and like today on Tuesdays and
Wednesdays for the mid week edition of the show. You can also cybersurf
to our website at rhc.cu, just that easy, just type rhc dot cu in your
browser window and then go to the English page to pick up our program
schedule. There you will also find the link to the Dxers Unlimited's
WebPages, with the scripts of the most recent shows for you to read...
Now, as always at the end of the program, when I am here in Havana and
can make the required solar optical and radio observations, here is
Arnie Coro´s Dxers Unlimited´s , exclusive and not copyrighted HF plus
Low Band VHF , from 30 to 50 megaHertz, propagation update and forecast.
Zero sunspots, more of the same, not a single one, not even trace of a
sunspot, a totally blank Sun for the past several days.
The geomagnetic field is expected to take a sharp jump to disturbance
levels as a consequence of a high speed solar wind coming from a
geoffective solar coronal hole, but the solar flux will also continue to
be at the bare minimum levels of between 65 and 67 units…
Solar activity at its lowest levels, no flares, no sunspots.
Amigos , I hope to see you all back here at the midweek edition of Dxers
Unlimited next Tuesday and Wednesday UTC days and don't forget to send
me your signal reports and comments about the show, as well as any radio
hobby related questions you may want to know about. send mail to inforhc
at enet dot cu, or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba,
Havana, Cuba
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