Re: [HCDX] Dxers Unlimited's weekend edition 22-23 December 2007

["Prof.Arnaldo Coro Antich" <coro@xxxxxxx>]

Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited weekend edition for 22-23 December 2007
By Arnie Coro
Radio amateur CO2KK


Hi amigos radioaficionados ! Seasons greetings and a Happy New Year 2008 
from Havana…
Welcome to the weekend edition of your favorite radio hobby program, 
coming to you from sunny Havana, where our mild winter weather, as usual 
  is providing us with beautiful days for going to the beach !!! I am 
Arnie Coro, radio amateur CO2KK, your friend here in Cuba, now ready to 
read today’s menu: ITEM ONE
The  expected  TV DX winter  season openings have happened, recently, 
with sporadic E skip events around the Caribbean becoming more and more 
frequent. At least two of the most recent sporadic E opening sent the 
maximum useable frequency up to the FM band, making reception of FM 
stations from more than one thousand miles away possible even with 
handheld radios and their telescopic whip antennas… More about the 
sporadic E season later. This is the winter sporadic E season that is 
much shorter and with less number of openings than the spring summer 
season,that is still several months away, due to start at the end of 
April as usual .. ITEM TWO: An amateur radio satellite designed to orbit 
the Earth using a very special elliptical orbit that would make it 
available for many hours at a time, just short of a geosynchronous 
orbit, the so called MOLNYA orbit, is an excellent choice for any 
upcoming new ham radio satellite. But it will cost a lot of money to 
build it. Such a MOLNYA orbit type of satelllite  will hopefully 
sometime in the distant future replace the doomed OSCAR 40, that had big 
problems from its very few hours in Earth Orbit.
ITEM THREE: Listeners questions continue to come in via e-mail, 
postcards, letters and fax messages, and I have quite a backlog of them 
here waiting to be answered… a recent one from Brazil, really surprised 
me, as normally the show is not heard so far South of Havana… But the 
use of 11760 kiloHertz with our high gain omnidirectional antenna 
explains why English speaking listeners from Brazil, Argentina, Chile, 
Uruguay and Paraguay and also Bolivia, among others, are picking up 
Dxers Unlimited.. ITEM FIVE: More about low cost , easy to build ham 
radio equipment, and at the end of the show, our exclusive and not 
copyrighted HF plus low band VHF from 30 to 120 megaHertz propagation 
update and forecast.Stay tuned for more radio hobby related information, 
coming to you from Havana. I am Arnie Coro ready to be back with you in 
just a few seconds after a short musical interval…
….
Si amigos, yes my friends, you are listening to Radio Havana Cuba, the 
name of the show is Dxers Unlimited, and YES, we do QSL here one hundred 
percent, we do verify reception reports and we do it absolutely free of 
charge, as all short wave radio stations should do… Send your signal 
reports and comments about the program to arnie@xxxxxx, or VIA AIR MAIL 
to Arnie Coro, Radio Havana Cuba,
Havana, Cuba, And NOW , here is ASK ARNIE, THE most popular section of 
Dxers Unlimited, according to your e-mails, postcards and letters amigos 
… QUESTION number one for today: From listener Desmond QTH Glasgow, 
Scotland, the UK…, Des wants to know why old radio magazines often 
mentioned the use of so called converters ahead of short wave receivers 
to pick up the higher frequency bands. Well amigo Des,as I explained 
recently here to a listener in Maryland , USA, a converter is nothing 
else but a complete front end of a radio receiver,that is built as a 
separate unit, in a separate box ,so that it can be connected between 
the antenna and the receiver and it usually includes a radio frequency 
amplifier stage, a mixer and a local oscillator. The RF stage in the 
case of converters designed to be used for the VHF bands used at that 
time,the best available low noise vacuum tubes that provided good gain 
and low noise, and the really good converters used a crystal controlled 
local injection oscillator. Even today, adding a homebrew converter 
ahead of a low cost receiver can provide outstanding results,it can 
prove to be a quite succesful effort especially with radios that lack 
front end selectivity or use a single intermediate frequency, the so 
called single conversion receivers. Not too long  amigo Desmond, I 
removed a lot of dust from a three transistors 10 meters band converter 
that was in storage for many years… it required just 12 volts DC to 
operate. Powering it up from one of my workbench power supplies , I 
connected the more than 30 years old germanium transistors converter to 
a modern digital portable receiver,the SONY ICF7600 and was pleasently 
surprised when I could pick up several 27 megaHertz 11 meters band 
Citizens radio stations as the band was open at the time of the test. 
Modern HF receivers are including extended tuning range  even up to the 
two meters amateur band, so these converters are not required with new 
receivers, but older radios that had a limited coverage to around 30 
megaHertz would certainly benefit with the use of a well designed 
converter. Anyway, for those of you like amigo Desmond that are 
interested in VHF converters, I may add that they are not too difficult 
to homebrew, especially if you use solid state devices . A typical more 
modern converter will use a high gain low noise MOSFET RF amplifier 
stage, a double balanced passive mixer and a bipolar transistor 
oscillator. It will be powered from 12 volts DC and when connected to 
even a low cost modern digital receiver, will turn the resultant 
combination into a rather nice VHF receiver , useful for monitoring 6 
meters during the summer sporadic E season. Remember to tune set the 
receiver to scan from 50.0 to 50.3 megaHertz where most of the activity 
on 6 meters is concentrated around the world.  QUESTION TWO, Came from 
the beautiful city of Bahia in Brazil, listener Marco Aurelio , who 
listens to our 9550 kiloHertz Caribbean edition, tells me in his e-mail 
that he wants to know more about the fan dipole antennas and why are 
they so useful when you can only install a single outdoor antenna at 
your location.. Well amigo Marco Aurelio, broadband fan dipoles are easy 
to build, they are easy feed with open wire line, and above all, receive 
only fan dipoles  can be built very easily and at low cost by anyone . 
Amigo Marco Aurelio, I am sending direct to you via e-mail the complete 
, step by step building instructions for my WIDE BAND FAN DIPOLE HF 
ANTENNA SYSTEM, so that you can start building yours and then tell me 
also via e-mail how it performs at your location.
The WIDE BAND FAN DIPOLE HF ANTENNA is possibly one of the lowest cost 
high performnce OUTDOOR antennas that exists, but it can also be used 
INDOORS too, in which case you will want to install a remote tuning 
ANTENNA TUNER system. Peaking the antenna tuner for maximum signal is 
quite easy to do, and at the same time it provides ultra-sharp 
selectivity right at the antenna, that helps a lot to reduce unwanted 
noise and cross modulation problems caused by high powered stations that 
affect low priced receivers so badly. As a matter of fact, using my WIDE 
BAND FAN DIPOLE ANTENNA with a low cost digital receiver proved to be a 
very interesting experience, as the radio’s performance was enhanced 
signficantly due to the extra selectivity at the front end provided by 
the antenna tuner system very sharp tuning.
QUESTION THREE, yes,  sent by listener Adalberto in Mexico |City, 
Mexico, he wants me to describe the design parameters for the low cost 
two element cubical quad antenna for the 2 meters amateur band. Well 
amigo Adalberto, using standard wire quad antenna elements , the small 
CUBICAL QUAD is fed with 50 ohm coaxial cable. The boom is made from PVC 
pipe of the type used for water distribution .The two elements are close 
spaced at only 25 centimeters separation from each other. This version 
of the CUBICAL QUAD  antenna has around 5 dB gain, a broad radiation 
horizontal pattern, is rugged and easy to build and will help you to 
access distant repeaters that can’t be reached using the typical 
handie-talkie helically loaded antenna, popularly known as rubber ducky 
because they look like the tail of a duck wagging !!!
The boom of the antenna is made from PVC pipe of the type used for high 
pressure water distribution, and is one meter long, so that you can hold 
the antenna to any support from the rear of the reflector element and 
keep it well separated from the supporting mast or tower.
Again the separation between the driven and the reflector loops is 25 
centimeters. And the wire loops are made using number 12 bare copper wire..
I feed this antenna with 50 ohm coaxial cable, and right after the 
feedpoint, I wind 8 turns of the coaxial cable to the boom of the 
antenna to make an RF choke.. the cable is then fed trough a hole in the 
boom to the rear of the antenna where it exits . I have made many of 
these antennas, and found out that they provide excellent performance, 
and when built using the above mentioned dimensions they are usually 
below 1.5 to 1 standing wave ratio even before any adjustments are made. 
They can be adjusted for almost perfect standing wave ratio by just 
sliding the reflector element back and forth across the boom, and then 
leaving it permanently  fixed at the spot that provides the lowest SWR.
Try to tune the antenna for minimum SWR using a VHF standing wave ratio 
meter, but again, you can use the antenna directly without any 
adjustments without fear of high SWR, by just carefully measuring the 
elements .
And now amigos, as always, at the end of the program, here is Arnie 
Coro’s Dxers Unlimited’s HF propagation update and forecast… Solar flux 
is hovering around 70 units and the A index was still a  around 8 units, 
and it may even go down later in the week.Solar flares are not expected 
during the rest of the week .But propagation conditions will take a turn 
for the worst  because of what scientists are forecasting as yet another 
long period of a blank Sun,.
Sporadic E openings are going to be more frequent as we approach the 
peak of the winter E skip season, so do monitor the low band TV channels 
for them. See you all at the mid week edition of the program and don’t 
forget to send me your radio hobby related questions, signal reports and 
comments .. send mail to : arnie@xxxxxx, or via air mail to Arnie Coro, 
Radio Havana Cuba, Havana, Cuba

---[Start Commercial]---------------------

Order your WRTH 2008:
http://www.hard-core-dx.com/redirect2.php?id=wrth2008
---[End Commercial]-----------------------
________________________________________
Hard-Core-DX mailing list
Hard-Core-DX@xxxxxxxxxxxxxxxx
http://montreal.kotalampi.com/mailman/listinfo/hard-core-dx
http://www.hard-core-dx.com/
_______________________________________________

THE INFORMATION IN THIS ARTICLE IS FREE. It may be copied, distributed
and/or modified under the conditions set down in the Design Science License
published by Michael Stutz at 
http://www.gnu.org/licenses/dsl.html