Re: [HCDX] Dxers Unlimited's weekend edition for 30-31 December 2006

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

Radio Havana Cuba

Radio Havana Cuba Dxers Unlimited's weekend edition

December 30-31 2006

By Arnie Coro

radio amateur CO2KK

Hi amigos radioaficionados around the world and in space Season's 
Greeetings and a Very Happy and Prosperous New Year 2007 for you all... 
I am Arnie Coro , radio amateur CO2KK, your host here in Havana, now 
ready to bring you short wave radio's most comprehensive radio hobby 
program.. The one and only that tries really hard to cover all aspects 
of this wonderful and fascinating hobby that you and I love... Now, 
talking about 2007, just around the corner... it's going to be solar 
minimum year, described by scientists as the Year of the Quiet Sun, 
something that we are already watching, as the daily sunspot count 
during the past seven days has gone down to ZERO in three of them...So, 
be prepared to deal with very low daytime maximum useable frequencies, 
and the bands above 20 megaHertz sounding just like another VHF band 
amigos !!!

Item two: Very low solar activity is good news for low frequency bands 
users that benefit from much less ionospheric absorption , something 
typical of extended periods of very low solar flux... Amateur radio 
operators that have enough space to install antennas for the 160 and 80 
meters band will be able to work some very nice DX all along this winter 
season, and as a matter of fact , some

of them are already having a good time working far away stations on 160 
and 80 meters... Likewise Tropical Broadcast bands Dxers are now able to 
pick up very weak stations half way around the world, like , for example 
listening in North America to Tropical Band stations in the Asia Pacific 
region.

More radio hobby related information coming up in few seconds when Dxers 
Unlimited's weekend edition, our last program of 2006 continues... I am 
Arnie Coro in Havana.

.......

Si amigos, yes my friends, even with a little portable radio receiver, 
powered from a set of batteries you can enjoy AM broadcast band Dxing 
from sunset to sunrise... As ionospheric absorption from the lower layer 
of the ionosphere just vanishes when the Sun sets at your location, AM 
broadcast stations located within the typical skip distance of up to two 
thousand kilometers will be heard even on a very low cost radio... As a 
matter of fact, some AM broadcast band Dxers accept the challenge of 
picking up the greatest number of DX stations using the simplest 
possible receivers. Going to the very extreme of this concept, some of 
them homebrew sophisticated crystal radio sets , using highly efficient 
high Q coils that provide amazing performance.

One of the most unusual crystal set circuits is the voltage quadrupler 
four germanium diodes detector, that provides a high sensitivity not 
possible when using the typical single diode detector used in classic 
crystal sets.

Item four: Our Technical Topics section will deal today with yet another 
HOW TO, that in my opinion is going to be rather useful for the many 
Dxers Unlimited listeners around the world that enjoy homebrewing 
antennas...

This HOW TO deals with how to wind antenna matching transformers that 
are able to step up or step down the impedance ratios .

A little mathematics is involved here, but it's quite logical and easy 
to remember.

A one to one matching transformer has the same number of turns in both 
the primary and the secondary. Now if you want to match an antenna 
system that has, for example 150 ohms impedance to a 50 ohms coaxial 
cable, the turns ratio of the transformer is 1.73 turns to 1... For 
those of you familiar with mathematics, YES, its the square root of 3...

Now the extremely popular four to one matching transformer that is used 
with standard 300 ohms loads to match the cheaper and more easily 
available 75 ohms coaxial cable, again, it's the square root of 4, or in 
other words two turns of the primary winding for every one turn on the 
secondary.

Likewise you can make your own nine to one and sixteen to one matching 
transformers, the nine to one transformer requires three turns on the 
primary for every turn on the secondary winding. While the very useful 
sixteen to one transformer that I use for matching the new version of 
the extremely popular Arnie Coro's Tilted Terminated Folded Dipole ... 
requires four turns in one of the windings for every turn of the other 
winding.

As you have already realized, you need to keep the ratio of primary to 
secondary turns to provide the required

step up or step down ratio...

Now here are two examples of typical broadband antenna matching 
transformers wound on ferrite rods.
For a transformer that is designed to match a 450 ohms line to a 50 ohms 
line, the ratio is nine to one... So I experimented winding 21 turns on 
the side of the transformer that is connected to the 450 ohms line, and 
seven turns on the side going to the 50 ohms line.

Using a small length of a ferrite rod from a broken down

portable radio, this transformer was tested very carefully and found to 
have very little loss, while providing an

excellent match from 5 megaHertz all the way up

to 25 megaHertz, and still be useable up to 30 megaHertz.

Learning more about broadband matching transformers will give you a very 
useful tool for working with antennas and transmission lines, one of the 
more than 80 ways, that you and I enjoy this wonderful hobby .... RADIO !!!

.......

You are listening to Radio Havana Cuba, the name of the show is Dxers 
Unlimited, and YES, you can start the New Year with a nice QSL card from 
us, verifying reception of this program amigos... Send your signal 
reports and comments directly to me arnie@xxxxxx, and don't forget to 
include your radio hobby related questions, that will be answered via 
e-mail as soon as possible and will also be part of the program in the 
most popular section of this show "ASK ARNIE"... and here it is , in our 
last program of 2006, ASK ARNIE, answering a question asked by listeners 
in 23 countries... and I think this is a record

for a single question... Our friends in those 23 countries

all want to know if Solar Cycle 24 is really going to be a very active 
one, and five listeners are hoping for a match with record breaking 
cycle 19 that had a peak average sunspot for a single month of 207... 
the highest ever recorded by solar astronomers... ANSWER: According to a 
very well documented scientific paper, solar cycle 24, due to start by 
the end of 2007 or a little later, is expected to peak with an average 
monthly sunspot count of no less

than 40 more than cycle 23...and some scientists say

that by the years 2009 and 2010 we may already be witnessing a very 
active Sun... Forecasts for the actual peak of cycle 24 are still not 
very precise, as researchers need to watch how the cycle starts up in 
order to make a more accurate forecast...

If you want to draw your own conclusions, get set for two more years of 
very low solar activity, so you will have more than enough time to 
experiment with low frequency bands antennas amigos !!!

.....

Antenna topics, the number three most popular section of Dxers Unlimited 
according to the e-mail messages and letters that I receive here at my 
e-mail account :

arnie@xxxxxx  and VIA AIR MAIL  to Arnie Coro, Radio Havana Cuba , 
Havana, Cuba... Yes, all who write regularly to my program agree that 
after ASK ARNIE, and the HF propagation and low band VHF update and 
forecast, the third most popular section of this show is the one devoted 
to antennas... And today , the antenna topics section will be devoted to 
a very compact and easy to

homebrew antenna for the frequency range from 110

to 150 megaHertz, that will give you nice reception of the VHF aircraft 
band and the 2 meters amateur band.

It is a vertically polarized FAN DIPOLE, made using

a center insulator from which three half inch diameter

elements are connected to each side of the insulator.

So, you certainly need a heavy piece of TEFLON or Polyethilene in the 
form of a block that must be

at least three quarters of an inch thick, that is 19 millimeters, in 
order to support the heavy weight of the six elements that form the antenna.

The elements are cut to a length of 60 centimeters

of about two feet, and they are all of the same

length. They are held to the center insulator using

stainless steel hardware, so as to reduce to a minimum

corrosion problems.

The center insulating plastic block has a hole in the

middle for the support boom. This is required because

the vertical broadband fan dipole has to be side

mounted on the supporting mast or tower, and

separated from it by at least 60 centimeters or two

feet, or better yet by three feet or about one meter

away from the mast or tower.

The antenna is fed with standard 50 ohms half

inch diameter coaxial cable RG213, and will provide

excellent reception of the VHF AIR BAND that

extends from 110 to 136 megaHertz, and also

will allow picking up point to point and mobile

services in the 136 to 144 megaHertz range, and

provide you with a nice almost omnidirectional

antenna for the two meters amateur band that will

provide a nice match to any amateur radio transceiver that you may want 
to use with this antenna.

By the way, a listener recently asked about VHF AIR Band monitoring, as 
he happens to own a SONY ICF 2010 that

has that band included, and he wanted to know if he

can hear planes even if he lives quite far away from

an airport... So, let me now use a little time here for

a second round of ASK ARNIE, and tell amigo Justin

from Montana, USA, that high flying commercial

jet aircraft can be heard at distances of up to 100

or even sometimes 150 miles away or more while

they check their flight path with Air Traffic Control

and if you happen to live within about 50 miles

from an airport, monitoring both the terminal , that's

the Air Traffic Control that takes care of the inbound

and outbound flights when they are flying below

a certain altitude , is a really fascinating experience...

Yes amigos, monitoring the VHF air band is one

of the three different ways that you can listen to

planes flying not only near your home, but also those that are crossing 
the oceans at high altitudes, and use HF single side band to communicate 
with the LDOC, or Long Distance Operating Centers...

And now, just before going QRT, here is our HF plus low band VHF 
propagation update and forecast amigos... Solar activity is very low, 
but moving up slowly, expect very quiet magnetic conditions for the next 
two days, but that may change by mid week. Nice AM broadcast band DX 
conditions during New Years Eve... Now I wish you all

a Very Happy and Prosperous 2007, and invite you to

keep listening to Dxers Unlimited, a labor of love for

the worldwide community of radio hobby enthusiasts...

Send you comments about the program to arnie@xxxxxx, and help me make it 
better during 2007 !!!


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