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[HCDX] Dxers Unlimited, 25 y 16 de abril, por Arnaldo Coro
Dxers
Unlimited
Saturday, April 25, 2009
Dxers
Unlimited weekend edition 25-26 April 2009
Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited's weekend edition for 25-26 April 2009
By Arnie Coro
radio amateur CO2KK
Hi
amigos radioaficionados around the world... big hello to all three
million PLUS of you nice people that like me enjoy this wonderful hobby
a lot !
Welcome to the weekend edition of your favorite radio
hobby program, coming to you via short wave and also from 05 to 07 UTC
as part of our streaming audio from www.radiohc.cu.
Here is
now our first news item... one lonely sunspot, , yes, a small lonely
short living sunspot, that according to scientists belonged to solar
cycle 24 broke the 25 days in a row of ZERO sunspots, but it vanished
after just a very short existence.
Some heliophysicists are optimistic after seeing that minute sunspot,
while others are not ...
In the meantime, we continue to watch , and the extended tail end of
cycle 23 continues to dominate solar inactivity.
Item
two: Sporadic E is here, and it came a bit earlier than usual...
reports from many dyed in the wool 10 meters band operators confirm E
skip openings at such odd hours as 10 or 11 pM local time.
I
also realized that a sporadic E layer was overhead of my station while
working on 40 meters and having two way contacts with stations located
just 50 to 200 miles away in the evening, something that can only
happen if there is a sporadic E cloud right overhead.
Item
three: Have you ever heard of Class E radio frequency amplifiers ?. If
not, it is about time to do an Internet search engine exploration and
find out about that type of super high efficiency amplifiers, that will
boost your signal tremendously while using minimum energy from the
power supply.
But NO, those Class E amplifiers are not LINEAR,
so they can only amplify a constant carrier... nevertheless they are an
excellent choice for operating CW under battery power.
Item
four: The StingRay 65 antenna for 2 meter band handie talkies will
boost both your transmission and reception at very low cost, as you can
homebrew it from half of a TV rabbit's ears antenna and the connector
used by your HT , plus a bit of epoxy resin and the usual dose of ham
radio ingenuity !.
Si amigos, there are more than 84 ways of
enjoying this wonderful hobby, and here at Dxers Unlimited you will
always be learning something new...be it how to build and install your
own backyard radio telescope to pick up Jupiter's radio signals ,or
assembling a simple one diode, plus one transistor and one integrated
circuit receiver that will be featured here today in our technical
topics section.
Keep listening to Radio Havana Cuba, as Dxers Unlimited continues in
just a few seconds...
.............
Si
amigos, you are listening to the weekend edition of your favorite radio
hobby program, Dxers Unlimited with yours truly Arnie Coro... and here
is as promised earlier our technical topics section.... The One Plus
One Plus One short wave receiver... a unique very simple project that
can be built during a few hours of your spare time...
I will start by describing this direct conversion receiver .
The
name comes from the fact that it uses one signal diode, one transistor
and one integrated circuit. So that's why I have named it the One Plus
One Plus One short wave radio.
This receiver does need an external antenna .
The
input circuit is formed by a simple resistive attenuator, and a dual
tuned bandpass input circuit , to which a signal diode is connected.
The signal diode acts as an ultra simple product detector, when it is
also fed with radio frequency energy coming from the one transistor
local oscillator.
At the output of the mixer we have audio
from the station that we want to pick up, and it is fed to the
integrated circuit audio frequency amplifier. This is a barebones
receiver by all engineering standards, but it is really amazing how
nicely it works when connected to an external antenna !
My
prototype's signal mixer product detector diode was changed several
times, in order to determine which type provided the best performance,
and I must say that the 1N914 and IN4148 series proved to be excellent,
with other types of diodes also working OK.
I even tested a
super high performance microwave diode, and at the other end, a type
1N34A that was built more than 55 years ago !
The most critical
circuit of this One Plus One Plus One short wave receiver is the local
oscillator, because it must be very stable in order for to receiver to
work properly.
As a matter of fact, one of the tests that worked very well was to use
a quartz crystal to control the oscillator's frequency.
I
happened to have an exactly 6 megaHertz frequency crystal, and using it
the One Plus One Plus One , I am able to receive our own Radio Havana
Cuba's transmitter that operates on that frequency.
The
frequency of the quartz crystal must be set exactly to six dot zero ,
zero, zero, zero, in order to be able to receive in the so called
exalted carrier mode , that requires an ultra exact local oscillator
frequency.
The experiment proved to be very interesting, as our
transmitter's operating frequency is kept within plus or minus two to
three cycles per second, because we use a very sophisticated frequency
synthetizer.
During the local morning hours here in Havana
when we use the 6000 kiloHertz frequency to broadcast the Despertar con
Cuba program in Spanish, I was able to keep the One Plus One Plus One
fully synchronized with the transmitter so the audio coming out of the
loudspeaker was of excellent quality.
Replacing the crystal
controlled oscillator with a field effect transistor variable local
oscillator , it was possible to pick many stations on the 40 meters
amateur band, using CW and single side band voice modes, and I could
also hear the digital modes, easily recognized around 7070 kiloHertz.
When
one of the local radio amateur visited my workshop recently and saw the
breadboard version of the One Plus One Plus One, he asked how it could
be further improved, and that started a long analysis about how direct
conversion receivers can be optimized, that lasted more than two hours.
At the end of the conversation he left with one of my hombrew
double balanced mixers, a pair of field effect transistors a low noise
audio transistor and a type LM380 integrated circuit audio amplifier,
that he soon interconnected producing a very nice performing direct
conversion receiver, that as expected is much more complex than the
ultra simple One Plus One Plus One radio from which he picked up the
design concept.
You can learn more about the One Plus One Plus
One direct conversion short wave receiver, by sending an e-mail to
inforhc@xxxxxxx, with the request for the One Plus One Plus One direct
conversion receiver files ...
..........
Si amigos, yes my
friends, oui mes amis... the spring and summer Sporadic E season seems
to be already in progress, and 10 meter band operators where the first
one to find out about the presence of those elusive patches of very
high ionization that move fast at altitudes of between one hundred and
one hundred and fifty kilometers above the Earth.
One way of
knowing that a sporadic E propagation event is in progress is by
monitoring the segment of the ten meters amateur band that is used by
beacon stations, that transmit automatic Morse Code identification of
their callsigns and locations.
Those of you that own amateur
transceivers with a scanning function, can simply set the low end of
the scan fro 28.1 and the high end to 28. 5, so as to maximize the
probability of finding activity of the band, not only from the beacons,
but also from hams that operate digital and single side band voice
modes from 28.1 to 28.5 .
When the 10 meters band is open by
means of the sporadic E skip , the distance that can be reached is
shorter than when the band opens via the much higher altitude F2 layer
, but anyway, it is certainly nice to hear the band open for DX !
Now
our next item, also related to the already in progress E skip signal,
this time it has to do with TV and FM broadcast band DX... TV DX from
stations located in the United States of America will change totally
when the analog blackout takes over, and only digital TV signals will
be on the air from the USA. TV Dxers that already are learning about
digital TV from far away locations , have told me that the digital
signals are not as enjoyable to watch because of the very nature of the
transmission mode.
The digital TV signals are seen OK maybe for
a while, then the picture freezes up, then it just vanishes, and there
is no intermediate condition... in other words, it is quite different
from analog signals that slowly fade in and out, without those on and
off switching that is present with the digital TV DX.
FM
broadcast band Dxers will continue to enjoy the analog stereo the way
it is, but in the future a new FM band broadcast standard may replace
it, something that like in the case of digital TV will require totally
different new receivers.
.......................
ASK
ARNIE, is now tied up with the HF propagation update and solar activity
report as the number one most popular section of the program...
according to the e-mail messages sent to inforhc at enet dot cu, or VIA
AIR MAIL to Arnie Coro, Radio Havana Cuba .
Here is ASK ARNIE
today, with a question sent by listener Vladia from Russia. Vladia
picks up our 6000 kiloHertz English language program when we are
broadcasting to North America,the signal travels over the North Pole
and reaches Vladia's home QTH from 05 to 07 UTC !!!
Vladia
wants to know why our signals on that band are stronger during certain
part of the year , and are much more difficult to pick up at another
times.
She refers that the periods around the spring and autumn
equinoctial seasons, when signals are much better than during the
summer season. She also explains that during the winter season, signals
of our 6000 kiloHertz frequency can be picked up much earlier in the
evening her local time, but the signals are not as strong as during the
spring and autumn seasons.
The answer to your question amiga
Vladia, is that the ionosphere goes through several seasonal changes
that are especially seen on very long range propagation of radio
signals.
And I must add that running 250 kiloWatts to an almost
20 decibels gain antenna, does help to enhance the reception at very
long distances.
And now amigos, here is our Dxer Unlimited's HF
plus low band VHF propagation update and forecast, that also includes a
solar activity report to help you plan your short wave listening and
amateur radio activities... Solar activity once again back to extremely
low levels, after the very short life of the high latitude sunspot of
cycle's 24 magnetic polarity. The E skip season is now picking up, and
that may lead to some nice short skip contacts on 20 meters, plus
longer range QSO's on the 10 and 6 meter bands. Expect a fast drop in
the maximum useable frequency about two hours after sunset your local
time... with the later arriving signals coming from the West and
Northwest of your location. Send your signal reports and comments about
the program
to inforhc@xxxxxxx or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba,
Havana Cuba
Posted by
Arnaldo Coro
at
9:49 PM
Labels:
Dxers Unlimited 25-26 April
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