Radio Habana Cuba
Dxers Unlimited
Dxers Unlimited's weekend edition for 13-14 August 2005
By Arnie Coro
radio amateur CO2KK

Hi mis amigos radioaficionados around the world! This is the weekend edition
of your favorite radio hobby program, the one and only covering every single
aspect of this wonderful way to enjoy your spare time : RADIO... and when I
say RADIO, I mean every single aspect of our hobby that involves in one way
or the other electromagnetic waves... from monitoring the mysterious extra
long wave natural radio "noise" to detecting planet Jupiter's signals ,
something that can be done with very simple antennas and receiving equipment
so simple in fact, that picking up Jupiter's radio emissions is one of my
favorite demonstrations when someone visits my shack at a time that Jupiter
is above the horizon... Si amigos, there are at least 78 different ways you
can enjoy radio... so let's start with one of them today: Following the
solar cycle... and I warn you all, this may be addictive... and is certainly
a very rewarding experience, as you will learn a lot about the complex
solar-terrestrial relationships that have such a great influence not only on
short wave radio propagation, but also in many yet unknown aspects to
mankind... Solar cycle gurus will tell you that watching the Sun's activity
on a day by day basis is very interesting, and once you master the basics,
then you can start making your own propagation analysis that will lead to
much more fruitful operating time... For example, every time a Cuban group
of radio amateurs organizes a contest station, I usually get a phone call,
or a call on the local Havana metropolitan most active 2 meter band repeater
about two weeks before the contest is going to take place... but don't think
that Cuban hams are the only ones, I have received requests for HF
propagation analysis and forecasts from contest operators in Canada, the UK,
and other countries... The main reasons for such requests are, first of all
antenna related, and in second place they are looking for advice on the
bands that are more likely to produce the best results during different
times of the day... There are several on line courses that will help you to
learn a lot about the solar cycle, and once you master one of them, your
capacity to produce accurate and effective HF propagation updates and
forecasts will increase significantly... Item two: Closely linked to item
one: Solar activity is at very low levels at this moment, and the effective
sunspot number on Friday was at the very low level of 17, while the mid
latitude A index, the geomagnetic disturbance indicator for latitudes below
40 degrees North or so, was at a nice an low 5, so you should expect rather
nice propagation on the three tropical bands, 120, 90 and 60 meters plus the
AM broadcast band... Item three: ASK ARNIE, la numero uno, the number one
most reported section of Dxers Unlimited will follow, after a brief musical
intercut...
Stay tuned, I am Arnie Coro in Havana
.......
Si amigos ! This is Dxers Unlimited's weekend edition and here is ASK ARNIE,
la numero uno, your most favorite section of the show, today's question came
from several listeners in the USA... they all ask my opinion about using a
triode , a pentode, a dual gate mosfet, a single gate fet or a common
bipolar transistor to build a regenerative detector...
Well amigos, here is my personal opinion, which is based on experimenting
with many different circuit configurations... I must admit that my favorite
and very effective regenerative detector is a pentode, using screen grid
control of the regeneration, and a very special Hartley circuit that has
also a second tap at the high impedance end of the grid coil, in other words
I connect the grid circuit not to the top of the coil, capacitor
combination, but to a tap, located about 15 percent down the coil winding,
so your grid tuned circuit has two taps, one for the cathode near the ground
end, and another one about 15 percent down the top of the grid coil... I
also use a rather small and extremely high quality capacitor for the grid
circuit...the value of about 22 to 33 Pico farads seems to work best for my
6AK5 dash 5654 vacuum tubes... The grid resistor that provides the best
results is between 4.7 and 10 mega ohms, and usually I do some tests to find
the optimum value for a particular circuit. The 6AK5 regenerative detector
all by itself, when coupled to a triode-pentode audio amplifier works very
nicely in the range from 400 kiloHertz all the way up to 15 megaHertz or so.
. but this detector provides the best results up to a frequency of around 12
megaHertz .... For the many of you now just learning about the high
performance regenerative receivers using vacuum tubes, there are several
excellent designs available at the GLOWBUGS website, again the name of the
site is GLOWBUGS, and you can find the URL by running a search on any of the
popular INTERNET search engines...
......
arnie@rhc.cu, si amigos, arnie@rhc.cu is my e-mail address where you can
send your radio hobby related questions for the ASK ARNIE section of the
program, your signal reports and QSL card requests, and also your ideas and
suggestions for improving this program... VIA AIR MAIL, send your postcards
to Arnie Coro, Radio Havana Cuba, Havana, Cuba... now here is our next item
of today's show... A new radio amateurs training course will be starting at
my radio club this weekend, the Plaza Radio Club will be hosting the 40
hours program for the third time. The previous two training courses had
excellent results when the participants took the official radio amateur
license test... all but one of the students passed with excellent marks, and
several of them are now on the air, after completing the paperwork required
to obtain the radio amateurs operators license first, and then their own
amateur radio station license... The Cuban radio amateurs rules and
regulations were recently modified so that not passing a Morse Code CW test
will not exclude the applicant from obtaining an operators license if the
the total sum of all the other test's add up to the 60 points passing mark..
The Morse Code CW test is for both receiving and transmitting at a five
words per minute speed, and this decision is in compliance with a recent
World Administrative Radio Conference that left to the decision of each
individual telecommunications administration to include or not to include a
Morse Code CW test for HF operation ... article S25 of the international
regulations is no longer valid, a logical consequence to the total
suppression of the CW Morse Code emergency transmissions around the world,
now replaced with much more sophisticated and highly effective satellite
based systems.. The " Academia del Radioaficionado " the Radio Amateurs
Academy , was one of the agreements of the 2004 Radio Amateurs national
convention that took place in Santa Clara, Cuba, with the participation of
delegates of all of our nation's radio clubs...
.....
Si amigos, you are listening to the weekend edition of Dxers Unlimited, and
YES, we do QSL a hundred percent, send your QSL requests to arnie@rhc.cu, or
VIA AIR MAIL send a postcard or letter to Arnie Coro, Radio Havana Cuba, and
Havana, Cuba. Many more radio amateurs in Cuba now, our hobby is growing
here, and several amateur radio organizations in Latin America and the
Caribbean are asking us, how have we achieved this growth, that is described
by some of them as absolutely amazing... The answer is not too difficult...
our grassroots organizations of the Cuban Federation of Radio Amateurs, the
municipal radio clubs promote the radio hobby, and then those people that
become interested in our hobby, receive a lot of support from other radio
club members, that include as I described a while ago right here, a
comprehensive training program " The Radio Amateurs Academy " that has
provided excellent results during the first two cycles of this activity.
Club members also help newcomers to homebrew their radios and antennas, or
to modify commercial equipment, like mobile FM transceivers, so that they
may be used on the VHF amateur bands...
We have several easy to homebrew antenna designs for the extremely popular 2
meters band, where many of the newcomers take their first steps after
obtaining their ham license...
.....
Now, here is the technical topics section of Dxers Unlimited, now ranking as
the number four most popular according to listener's correspondence, closely
following QSL on the air... Today I will tell you about an electronic device
a passive electronic component that provides added protection to all
electronic equipment... These passive devices have several commercial names,
like TRANSZORBS, Transient Suppresors, NoSpike, etc, and they are
essentially specially made non linear resistors made of semiconductor
materials, that act as peak voltage limiters when connected across a circuit
Their most frequent application is as line voltage spike protectors, and
nowadays a lot of electronic equipment includes them at the power line input
.. One of the most interesting features of these spike or transient
suppressors is that they are designed to fail into a so called heroic
failure mode, shorting out the input so that the protecting fuse will blow
if the spike reaches the device's preset limit for a certain period of time.
. Practically all computer power supplies use these transient suppressors,
but surprisingly home brewers and commercial amateur radio rig designers don
t include the semi-conductor transient suppressors in their designs... and
that's the reason that my advice is for you to take a look at your power
supply, and see if it is already fitted with a transient suppressor, and in
case you don't fine any, go ahead and add not one but two or even three of
them , properly rated according to the power line input voltage..
And now amigos, like always at the end of the show when I am here in Havana,
here is our exclusive and not copyrighted, in the public domain, HF
propagation update and forecast, together with low band VHF information too.
. Solar activity is at very low levels, and a coronal hole that can be seen
very well by solar researchers may be impacting the Earth's magnetosphere
with a high speed solar wind that could be reaching here by late Monday or
Tuesday... if this happens, then HF propagation conditions will deteriorate,
especially a high latitudes... Solar flux was around 75 units on Friday,
quite close to the 70 figure that is considered by researchers to be the
baseline of the Sun...I have received several reports of sporadic E events
during the period from Monday to Friday, and these ones may be the last
openings of the summer season. We are now about a month away from the
upcoming autumn equinox, when propagation conditions will be much better
than now... Hope to have you all listening to the mid week edition of the
program next Tuesday and Wednesday UTC day, and please don't forget to send
me your signal reports, and comments about Dxers Unlimited to arnie@rhc.cu
or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba...