[BARC-List] DXers Unlimited via KA1RDZ

Dxers Unlimited 
Dxers Unlimited’s week end edition for 18-19 February 2006 
By Arnie Coro 
Radio amateur CO2KK 


Hi amigos radioaficionados ! Welcome to the weekend edition of your favorite
radio hobby program, I am Arnie Coro in Havana, and here is item one: Solar
activity went up by just a little bit, but it’s no more ZERO sunspot count
my friends
 Plus, there is a possibility of a high speed solar wind gust
from a coronal hole hitting the Earth’s magnetosphere soon. As many of you
long time Dxers Unlimited’s fans have learned by listening faithfully to our
HF propagation updates and forecasts, a high speed solar wind full of
protons may generate a magnetic storm, so be ready to monitor the higher
frequencies of the HF spectrum for any signs of propagation disturbances

Item two: Amateur radio operators from all around the world are very happy
with the 3YOX Peter Island DX expedition
 According to Cuban DX Group member
Raul Verdecie CO8ZZ, the DX station located near Antartica is delivering
very nice signals on all bands where propagation is possible. Also Juan
Carlos CO2JD, one of our top notch CW radiotelegraphy operators has kept
Cuban amateurs informed trough the Marianao Radio Club Digital Bulletin. But
so far, due to a very tight work schedule here at Radio Havana Cuba and at
the University where I teach, CO2KK, my ham radio station has yet to add
3Y0X to the logbook. And there is not too much time left for me, as the DX
expedition will be soon departing the isolated , ultra-remote island, that
has been visited so far by less number of persons that the Earth’s outer
space !!! 
Item three: Another one about TV DX
 North America TV Dxers have seen now
several high barometric pressure areas that produce wonderful tropospheric
enhancement of TV signals on the VHF and UHF bands. Here in Havana, our Jose
Marti International Airport ATIS, that is the Air Terminal Automatic
Information Service was reporting to pilots a 1024 millibars altimeter
setting on Wednesday, and sure enough, VHF tropo signals were present on the
two meters amateur band
 
More radio hobby related items will follow after a short break. This is
Radio Havana Cuba, and you are invited to stay right on this frequency , or
stay connected to our www.radiohc.cu website streaming audio
 

. 
Si amigos, this is Dxers Unlimited’s weekend edition, and now , item four of
today’s program: A big THANK YOU to the many listeners that have sent e-mail
messages, postcards, letters, and FAX letters reporting the show, and giving
me so many good ideas about topics to talk about here. I am sorry to say
that again there is a bit of a backlog in answering the correspondence, but,
don’t worry, I will catch up during the week end
 after running the HF
propagation software many times to try to catch the 3Y0X DX expedition to
Peter Island at least on one band. Item five: For about five years now, the
topic of homebrewing radio receivers has being the number one at the top of
the list here
 and I believe there is a good reason for this happening, as
more and more radio hobby people are learning that receivers can be built
with readily available parts, and that even very simple circuits will bring
a lot of enjoyment when you connect them to an antenna
 THE, with capital
letters,the two most popular project for homebrew receivers that I have
promoted here are the AUSTRALIAN FUN, or Moorabin solid state regenerative
receiver in its two variations, and the many designs of REGENERODYNE
receivers that had been built and used by Dxers Unlimited’s fans around the
world. Looking at Dxers Unlimited’s archives, I found this letter from a
Canadian listener, that is a very good example of why I still promote this
rather unconventional receiver design, the REGENERODYNE, here is, copy and
paste from a Dxers Unlimited edition way back in April of 2001, almost FIVE
years ago
 Here is what the Canadian radio hobby enthusiast said: 
Arnie, I had built regenerative radios in the past, both vacuum tube and
solid state, but you know, although they worked, and some worked rather well
they are nothing compared with even my first very crude regenerodyne...
keep up the good work, and why don't you try to write a little book about
the regenerodyne receivers....   signed, DXers Unlimited's fan from Ontario.
This led to my answer to him, that reads as follows: 

Well amigo, I agree with you that even the simplest and quite
straightforward regenerodyne receiver out-performs the best of regeneratives
many times over.... My latest experimental regenerodyne has one very
interesting feature: I can either plug in a coil that will let me listen to
a full 2 megaHertz segment of HF, or plug in another one that is a
bandspread coil, fashioned after the famous National Company HRO bandspread
coils, that lets me tune just the first 100 kiloHertz of any given segment.
See, for general short wave listening one uses the full coverage coil, and
for tuning to the CW portion of the amateur bands, then one uses the
bandspread coil. By the way, this particular regenerodyne receiver is using
some nice computer quartz crystal oscillators to generate the local
oscillator frequencies.... so this is the first hybrid regenerodyne, using
both vacuum tubes and solid state devices. I am using a 4.000 megaHertz
oscillator now, but plan to include a simple switching arrangement to use
several similar oscillator modules, extending the range of the frequencies
that the regenerodyne can pick up. 

For those of you still not familiar with the regenerodyne receivers, they
are nothing more than a conventional front end, that is an RF amplifier,
mixer and local oscillator, feeding not standard Intermediate Frequency
amplifiers strips and detectors, but instead connected directly to a very
carefully built regenerative detector stage that tunes anywhere from a 100
kiloHertz segment of its tuning range to a maximum of about 2 megaHertz...
SO, as you may realize, the regenerodynes are a very special kind of radio,
combining the best of the superheterodynes with that very wonderful circuit
invented by Edwin H Armstrong, known as the regenerative detector!!! 
Almost five years have gone, and REGENERODYNE receivers have become
extremely popular among homebrewers of radio equipment. The most recent
circuit I had the opportunity of seeing and operating was a unique 
VHF receiver, consisting on a solid state front end for the two meters band,
connected to a regenerative detector operating between 4 and 6 megaHertz.
The  detector is very well shielded, and shows very little leaktrough from
the 2 meters antenna. The front end uses a MOSFET dual gate device, with a
signal attenuator, a four diode double balanced mixer and an injection
oscillator formed by a computer clock module and a bipolar transistor
multiplier. 
The computer clock frequency came from a dead 486 motherboard, and runs at
50 megaHertz, and is followed as already explained by a multiplier to 150
megaHertz. The 144 to 146 megaHertz segment of two meters is picked up by a
REVERSE tuning regenerative detector, that meaning that 144 megaHertz is
picked up at the minimum capacity of the variable capacitor, on 4 megaHertz,
and the 146 megaHertz is heard on 6 megaHertz because the local oscillator
frequency is injected above the frequency you want to listen to. This two
meters band REGENERODYNE picks up CW, AM, and the much more popular on two
meters narrow band FM signals from ham radio operators. It is used by a
Cuban radio amateur to monitor a distant repeater where he has many friends
and relatives that are also radio amateurs. In his two way recent QSO, with
me on two meters FM, he said that his radio is amazingly stable and provides
room filling audio from the triode-pentode ECL82 audio section. The whole
lineup of this receiver is as follows:  Dual gate MOSFET radio frequency
amplifier stage with a dual tuned bandpass input filter and attenuator,
feeding a broadband four diode balanced mixer. The injection oscillator is a
computer clock module operating at 50 megaHertz, connected to a bipolar
transistor tripler, that in turn feeds a 150 megaHertz amplifier that
injects that signal to the mixer at a PLUS seven DBM level. The output of
the mixer goes directly , via a variable link to the regenerative detector
stage that tunes from 4 to 6 megaHertz. This stage uses a Hartley type of
regenerative detector that delivers the audio to the triode-pentode ECL82.
The receiver was built from mostly recycled parts, and no attempt was made
to miniaturize the set. The power supply presently in use was built on a
separate chassis, so that it could be used with other projects too
For those
of you interested in this project , plans are in the works to write a small
PDF document with the circuit description, electronic diagrams of the three
modules, that is the converter from two meters to the 4 to 6 megaHertz
segment, the 4 to 6 megaHertz regenerative detector and audio amplifier
module and the power supply. Our project is to include also photos , and
even the printed circuit lay out of the most critical part of this radio,
that is no doubt, the front end
 As soon as this is done, I will announce it
here during a Dxers Unlimited program, but if you are really motivated by
this description, then you can certainly send me an e-mail and I will put
you on a mailing list , so that as soon as the PDF document is ready, it
will be e-mailed to you. 
By the way, according to a long time friend, and top notch telecommunications engineer, this receiver design is also ideal for monitoring the SIX meters band for DX, by keeping it tuned to a center frequency of 50.125 megaHertz the calling frequency most used here in the Americas by SIX meters operators