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Re: [HCDX] Dxers Unlimited's script for the mid week edition of 13-14 February 2007
Radio Habana Cuba
Dxers Unlimited
Dxers Unlimited's mid week edition for 13-14 February
By Arnie Coro
radio amateur CO2KK
Hi amigos ! Welcome to the mid week edition of your favorite listener
oriented,and technically minded radio hobby program.
This is your friend in Havana, Arnie Coro, radio amateur CO2KK ready to
spend about seventeen minutes of on the air , on the
web and also now on the satellite time... Our satellite broadcast
can be heard in English from 05 to 07 UTC on Hispasat 1 D
transponder 79, where you can also pick up other Cuban
radio stations and several of national TV networks, including
Cubavision Internacional, our international TV channel... Now here is
item two: Among the most rewarding moments in anyone's radio hobby
career , making the first two way amateur radio contact qualifies way
up, it's second to none, but closely followed by that unique sense of
achiement when a radio you have assembled from a kit or built from
scratch starts picking up stations... But don't forget antennas...
because when you finish building and installing a new antenna, and
connect it to your radio, all those signals are really a reward to your
dedication to the radio hobby.
Monday afternoon I was at my across the street neighbor QTH. Francisco
is a retired person , who has become interested in our hobby in a very
peculiar way. He wanted to built his own TV antenna to pick up Havana's
our UHF stations, that operate on channel 15, 27 and 44, and sure
enough, he asked me for a simple design, that he was able to build in a
couple of hours. The antenna that I recommended was a simple two element
cubical quad, cut for the center of the VHF HI TV band, that spans from
174 to 216 megaHertz, because he wanted to receive those channels too,
and the quad cut for that frequency range happens to work also quite
well for receiving the UHF channels that are located around the third
multiple of the channels 7 to 13 TV band. Now Francisco has become a
very popular person in our neighborhood, because his "two squares"
little antenna is picking up the five Havana TV stations pretty well,
and it is at the same simple and easy to build, while requiring easy to
obtain materials... as a matter of fact it can be built from a recycled
TV antenna !!!
More about homebrewing antennas in a few seconds when Dxers Unlimited's
mid week edition continues...
Stay tuned or connected to our streaming audio from www.radiohc.cu...or
if you are picking up this program via Hispasat ID, stay on our audio
feed...
......
Si amigos, this is Radio Havana Cuba, the name of the show is Dxers
Unlimited, yes we are still sending our beautiful 45 th Anniversary of
Radio Havana Cuba conmemorative QSL cards u... Send your signal reports
and comments to arnie@xxxxxx or VIA AIR MAIL, send a postcard or letter
to Arnie Coro, Radio Havana Cuba, Havana, Cuba...
Now more about homebrewing antennas... one of the more than 80 ways of
enjoying our wonderful hobby... As I said a while ago , my across the
street neighbor has started to build several more TV antennas for people
living even several blocks away, and he is now becoming interested in
learning more about amateur radio, as the topic came across when I was
showing him a new antenna I had just finished building for the 2 meters
band. Here in Cuba you can obtain your amateur radio beginners license
that will give you a call sign that starts with CL, by passing a course
at the local radio club, and then taking a Ministry of Informatics and
Communications official amateur radio operator test. Now the CW Morse
Code Test is at only 5 words per minute, and it is not excluding, in
other words it gives you a certain number of points , but if you fail
the Morse Code test and make well on the rest of the test, then you will
pass the exam and be able to apply for your amateur radio station license.
Among newcomers to the hobby here, the 2 meters band is the favorite
one to operate, as with little power and simple antennas you can work
many stations using repeaters, and when propagation conditions are good,
you can work simplex contacts with stations hundreds of miles away.
Two meter band gain antennas are easy to build, and they are about the
same size, actually just slightly larger than TV antennas used for
receiving the TV stations that operate on channels 7 to 13....
......
Homebrew receivers, radios that are built from electronic components
and that you assemble yourself, bring in signals that have a special
sound of sorts, special in the sense that when signals come out trough
headphones or loudspeakers of those homebrew radios that started to
operate after many hours of a unique learning experience, you feel a
sense of accomplishment second to none. And let me add that after many
years of homebrewing radios, from the simplest to the most
sophisticated, by homebrew receivers keep that special sound all the
time!!! For example, my prototype vacuum tube regenerodyne, originally
built fifteen years ago, is still a joy to operate. All along its life,
I have done a lot of experiments with it by changing the tuning coils,
the values of some critical components and even vacuum tube types, so it
has acted as a test bed of sorts... But, it still gets used , especially
during the weekends, when on Sunday mornings I enjoy operating on the 40
meters band using the single side band voice mode to talk to my many
friends all along the Cuban archipelago that are active on the several
nets operated by provincial radio clubs.. My prototype regenerodyne has
one of the plug in coils configured for bandspread coverage, optimized
for covering just the lower 150 kiloHertz of 40 meters, where the nets
operate.
.....
Si amigos, this is Radio Havana Cuba, the name of the show is
Dxers Unlimited and today our number one most popular section ASK ARNIE
, will be providing you with a detailed description of not one , but two
regenerative receivers that are rather easy to homebrew and provide
excellent performance... First you will listen to the data about the
KK-12 REGENERODYNE vacuum tube multi band receiver and then I will be
describing the Desert Rat Three, a 1996 design, that is, according to
all my tests the best solid state simple regenerative circuit design ,
the brainchild of well known American radio amateur and short wave
listener Paul Harden NA5N
Now let's start with the KK-12 Regenerodyne that so many of you have
asked about lately. The final version of this radio receiver uses a dual
tuned bandpass input filter and signal attenuator, that is connected to
the grid of a radio frequency amplifier vacuum tube that provides very
little gain, as its main function is to provide isolation to the mixer
stage that follows it. The other signal for the mixer is provided by a
simple quartz crystal oscillator that is capable of using many different
types of crystals in many different types of holders... So, the front
end of the KK-12, is conventional , but very well designed... The output
of the mixer is fed to the variable frequency regenerative detector
stage,that uses a Hartley type detector with screen grid voltage
regeneration control...The audio output from the detector is fed to a
two stage audio amplifier, that in the original prototype was made using
two individual vacuum tubes that were at hand, a 6C5 and a 6V6. But the
latest version , which is the one in use now uses a triode-pentode
vacuum tube contained inside the same glass envelope. Summarizing, the
vacuum tube line up is as follows, a 6BA6 or similar pentode RF
amplifier stage , a 12AT7 or the equivalent ECC81 in a Pullen Mixer
configuration , a 12AT7 crystal oscillator and cathode follower, a 6BA6
or similar regenerative detector and a ECL82 or similar audio pre-amp
and audio power amplifier stage. The radio uses a homebrew solid state
power supply with some special characteristics... Its maximum B +
voltage is 140 volts DC, it provides plus 75 volts regulated DC for
feeding the regenerative detector stage, and 6 volts DC for the
detector's and the audio amplifier stages filaments, in order to keep
the presence of 120 cycle HUM really low. With today's solid state
diodes and integrated circuit voltage regulators plus the availability
of high values of electrolytic capacitors, this power supply is almost
like powering the receiver from a pair of B batteries and an accumulator
for the filaments, like in the early days of radio, but without having
to worry about changing the B plus batteries or recharging the
accumulator !!
The radio was built without any attempt to make it a compact or
miniature set, plenty space was left between the parts, so as to make
experimenting easier. The regenerative detector in this final version is
capable of tuning to several frequency ranges... With one "bandspread
coil" it tune from 2.0 to 2.15 megaHertz, that is from 2000 kiloHertz to
two thousand one hundred and fifty kiloHertz, that when mixed with a 5
megaHertz crystal provide excellent bandspread coverage of the first one
hundred and fifty kilohertz of the 40 meters amateur band, changing the
crystal to 8 megaHertz, that by the way is a very common computer
surplus quartz crystal, the the radio tunes to the 30 meters band, and
provides you with a nice propagation indicator, as you can pick up the
time and frequency standard stations that operate on 10 megaHertz, that
serve as a reliable calibration source...A third crystal, that
oscillates on 12 megaHertz provides reception on the first half of 20
meters, making reception of CW stations found at the low end of 20 very
easy.
But the KK-12's plug in detector coils feature also gives you the
possibility of tuning to one or two megahertz wide segments of the short
wave spectrum. Changing the detector coil to the general coverage one,
and using the 5 megaHertz crystal, you can tune from seven to eight
megaHertz , or from three to four megahertz according to the setting of
the bandpass input tuning filter... Every crystal offers the possibility
of two tuning ranges, one that comes out when you add the frequency of
the crystal to the frequency of the detector, and the other one, that
appears when you subtract the frequency of the detector from the
frequency of the quartz crystal.
And now amigos, as always at the end of the show, here is our exclusive
and not copyrighted HF plus low band VHF propagation update and
forecast, to help you optimize your listening and ham radio operating
times... Solar flux at very low levels… optical sunspot observations for
the past two days show ZERO SUNSPOTS… and we may be seeing a geomagnetic
disturbance during the next two days due to a high speed
Solar wind coming from a coronal hole. Solar flux expected to be below
75 units, and that combined with ZERO sunspots is bad news for the
maximum useable frequency daily curve’s peak… It’s going to be very low
indeed… Hope to have you listening to the weekend edition of the
program, and don’t forget to send me your signal reports and comments
and any radio hobby related questions to arnie@xxxxxx or VIA AIR MAIL to
Arnie Coro, Radio Havana Cuba, Havana, Cuba…
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