Re: [HCDX] Dxers Unlimited´s weekend edition for 22-23 March 2008

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

Radio Havana Cuba

Dxers Unlimited

Dxers Unlimited´s weekend edition for 22-23 March 2008

By Arnie Coro

Radio amateur CO2KK

Hi amigos radioaficionados around the world, and in space at this 
moment…welcome to the weekend edition of your favorite radio hobby 
program, the one and only covering the more than 83 different ways that 
you and I enjoy playing with our radios… From the Canadian AM broadcast 
band Dxer trying to set a new record of stations heard on a very small 
portable radio, to the Cuban newcomer to amateur radio that yesterday 
visited me to return the 2 meters band MOXON rectangle antenna that I 
lent to him so that he could go on the air the very same day that he 
received his amateur radio license… Si amigos, yes my friends, you can 
be sure that people do enjoy this hobby a lot, and even when the going 
gets difficult , like the day our small fishing vessel that was taking 
us to the CO4 Dx expedition of 1965 ran aground and water started to 
come into the hull, instead of panicking, we simply used our ham radio 
equipment to call for help, as at that time we had no VHF Marine radio 
coverage in that area of the Cuban archipelago. Radio brings in so many 
nice moments, that recalling some of them while spending a nice 
afternoon at our radio club becomes part of our lives… Now let me give 
you a nice example of how radio has help a lot of persons to live a 
better life. For people with poor vision or that are totally blind, 
amateur radio is a great hobby that makes possible for them to meet 
friends, participate in contests and share with others their ham radio 
experience… For highly qualified engineers and telecommunications 
technicians , the radio hobby makes possible to perform some very 
interesting experiments using the amateur band frequencies… some of 
those experiments have become classics, like the ones made by a group of 
retired professional

Radio broadcast engineers that fully documented the dramatic improvement 
in performance for vertical antenna systems provided by elevated radials…

Amateur radio operators have even made some very important discoveries 
in the area of radio wave propagation, and experiments that were done by 
amateurs demonstrated the existence of what we now know as Trans 
Equatorial Scatter Ionospheric Propagation, or just TEP for short, a 
fascinating communications mode that so far has defied theoreticians …

Stay here with me, as the weekend edition of Dxers Unlimited will 
continue in a few seconds… I am Arnie Coro in Havana..

………

You are listening to Radio Havana Cuba, the name of this show is Dxers 
Unlimited and if you happen to be a first time listener, bienvenido, 
bienvenue, welcome amigo !!! Its nice to have you join the ever 
increasing group of radio hobby enthusiasts that listen regularly to my 
program and communicate with me via e-mail, or on the air via amateur radio.

Here is now one of the most popular sections of the program… The antenna 
topics segment, that today will be devoted to part II of low cost 
broadband antenna systems. During the mid week edition of the show, I 
gave a lot of information about the FAN DIPOLE, and of its three most 
popular versions, the one designed for coverage of the 3 to 10 megaHertz 
part of the short wave spectrum, the one for 6 to 18 megaHertz , 
certainly the most popular design according to your e-mail messages and 
letters, and the small compact FAN DIPOLE that works nicely from 
approximately 13 to 39 megaHertz. At the present moment, and as we are 
enjoying beautiful weather here in Havana, I am getting ready to 
re-install a slightly modified version of the 6 to 18 megaHertz FAN 
DIPOLE, this one is a little shorter than the standard model, due to the 
fact that the two supporting towers are a little bit too close to each 
other. Anyway, the antenna should perform well, something I expect to 
verify when it is up… By the way the latest analysis of solar activity 
by experts is telling us that we will again have to deal with an 
extended period of extremely low solar activity and absolutely quiet 
geomagnetic conditions…

Now, let´s move on to the second broadband antenna, that is perhaps 
better known and more popular among short wave listeners and 
professional HF communications systems, the TTFD or Tilted Terminated 
Folded Dipole , so well researched by L.B. Cebik, who is offering at his 
website a treasure chest of antenna related information… the URL is 
www.cebik.com <http://www.cebik.com/>, again slowly and in phonetics… 
Charlie, Echo, Bravo, India, Kilo, symbol for period, Charlie Oscar 
Mike…. Look for the information about the TTFD antenna, and you will 
find some very interesting comparisons between different lengths of 
these unique broadband antennas . The TTFD, as I have said here many 
times, is a compromise antenna system, a good choice if you can only 
install a single antenna and want to cover a wide frequency range.

For example, a 15 meters long TTFD will be a good choice if you want to 
monitor the HF bands from 6 to 30 megaHertz , and it will work quite 
well, with the help of a simple antenna tuner, for transmitting between 
the seven megaHertz or 40 meters amateur band and 29.7 the top end of 
the 10 meters ham band.

Now, one more important thing to take into consideration… a TTFD antenna 
that will be used only for receiving , can be made using 2 Watts non 
inductive resistors , that will have a total value of between 600 and 
1000 ohms. After many experiments it was found that for receive only and 
QRP low power transmission up to 5 Watts , a very good approach is to 
place two large sized two watt carbon resistors of between 300 and 500 
ohms in series to create a new equivalent resistor of between 600 and 
1000 ohms. The two resistors can be placed inside a length of heat 
shrinking plastic tube, and then attached to a good quality insulator 
that will take the strain from the upper wires of the antenna… If you 
want to operate the TTFD with transmitters of more than five Watts, my 
suggestion is to search for high quality high power non inductive 
resistors in the 50 to 100 Watts power dissipation range…A pair of 50 
Watt non inductive 300 ohms resistors connected in series, will provide 
an excellent terminating resistor for transmitter in the 50 to 200 Watts 
input power, and I want you to know that 300 ohms non inductive 
resistors are about the easiest to find of this usually hard to find 
components.

You will also need to homebrew a balanced to unbalanced radio frequency 
broadband transformer, better known among radio engineers as a BALUN… 
balanced to unbalanced abbreviated…

The balun for the TTFD antenna needs to be either a 12 to 1 or a 16 to 1 
, according to experts.But I have achieved good results when using a 9 
to 1 balun.

As antenna ¨¨guru ¨¨ L.B. Cebik justly affirms, some radio hobby 
enthusiasts claim that the TTFD picks up less noise than a standard 
dipole or long wire, something that I fully back, especially in the case 
of the long wire antennas…The TTFD picks up less local noise than a long 
wire and a dipole.

I have written a set of step by step instructions on how to make your 
own TTFD, that can be sent via e-mail as a compact, rather

small attachment, so if you really want to test drive the TTFD antenna 
system for short wave reception, just send me an e-mail to arnie at rhc 
dot cu, and I will send you the computer file as a compact e-mail 
attachment…

………

Si amigos, yes my friends, oui mes amis, this is the weekend edition of 
Dxers Unlimited and here at the request of several listeners is 
information about the Radio Rebelde´s short wave broadcasts… Radio 
Rebelde is now only operating on 5025 kiloHertz with 50 kiloWatts and 
its Tropical Band high take off angle main lobe antenna. The daily 
morning and mid day transmissions are no longer on the air. So, again, 
for your information, Radio Rebelde´s only short wave outlet that is 
operational at this moment is on the 60 meters Tropical band , on 5025 
kiloHertz and this transmitter is on the 24 hours, to provide primary 
sky wave service to all of the Cuban archipelago…

And another Cuban broadcast related news item, Radio Angulo, the Holguin 
provincial network is now with two ten kiloWatt transmitters, one on 740 
kiloHertz and the other one on the long time 1110 kiloHertz. The new 740 
kiloHertz relay of Radio Angulo is also a 24 hours operation and it is 
located in Sagua de Tanamo, a mountains region of the province , where 
the use of a lower frequency on the AM band should improve the coverage.

Now here is our next item here at the weekend edition of your favorite 
radio hobby program. Cuban radio amateurs are now involved in a revival 
of home construction of ham radio equipment, including receivers, 
transmitters, transceivers, antennas and station accessories. A national 
competition will award nice presents to the best entries on each 
category. Among the most popular entries are the ones focusing on the 
homebrewing of rigs for the 160 meters band, that are intended mainly 
for local communications. My own entry into the national event is going 
to be the DX-160, a simple, easy to build, rugged and reliable 160 
meters band CW transmitter that also has a high efficiency screen grid 
controlled carrier modulator so that it can be used for local AM phone 
contacts. The original Arnie Coro´s DX-160 dates back to the 1960´s and 
I made many nice two way CW DX contacts on 160 meters using it… Now 
after many years of storage, the announcement of the home brewing 
competition, made me remember about that rig that is at this moment 
sitting on top of the main workbench undergoing a major overhaul !!!

Homebrewing ham radio equipment is a lot of fun, I can assure you, and 
all two way contacts made with radios that you have built yourself have 
a very special significance… it seems like they sound a lot better than 
expensive commercially built rigs !!!

Try it, and you will certainly agree with me !!!

And now as always at the end of the program here is Arnie Coro´s Dxers 
Unlimited´s HF plus low band VHF propagation update and forecast… Solar 
activity is and will continue to be at very low levels as we pass trough 
the equinox … so, don´t expect much DX , because the ionosphere is in 
totally flat state… We may have short openings on 12 and 10 meters, and 
that´s about all for higher bands DX… while at the same time , local 
noise levels continue to increase as the summer thunderstorm season 
approaches… See you all at the mid week edition of the show, Tuesday and 
Wednesday UTC days , and don´t forget to send your signal reports , 
comments about the program and radio hobby related questions to arnie at 
rhc dot cu, or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba


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