Dxers Unlimited's weekend edition for for 28-29 November 2009
By Arnie Coro
Radio Amateur CO2KK

Hi amigos radioaficionados... welcome once again to the weekend edition of your favorite radio hobby program, I am Arnaldo, Arnie, Coro, radio amateur CO2KK, your host here in Havana and as always it is really nice to be able to share with you about seventeen minutes of on the air and on the world wide web time... Here is now item one... four days in a row without sunspots...once again the Sun comes to a standstill, and so far no one can explain the strange behavior or our nearest star... Solar cycle 24 now almost two years after it began is registering extremely low levels of activity, with the expected negative impact on short wave propagation conditions.... Item two... QSL on the air, QSL on the air to amigo Sean Catney from Canada... he sent me a very nice report that I will be sharing with you right now... Amigo Sean says in his e-mail, and I quote

My name is Sean Catney. I am an avid shortwave listener living in
Brampton, Ontario, Canada.
(Just outside of Toronto). I had the pleasure of monitoring your station today while you were conducting your daily broadcasts. My reception was made around 0130 Hours UTC on the date of Wednesday, November 25, 2009 on 6000khz. The signal was around
S8 with a slight fade. Shortly after 0130 UTC the world news began. Some of the headlines included: 1. The British inquiry into the Iraq conflict has officially begun. 2. Brazilian President affirms his belief
that Iran should be allowed to develop a peaceful, civilian nuclear
program. 3. U.S. President Barack Obama quietly supports controversial provisions of the Patriot Act allowing the FBI broad
surveillance powers, despite the objections of the ACLU and other civil rights groups. At 0135 UTC a weekly sports report began. At 0140 UTC my favourite show, Dxer's Unlimited began with Arnie Coro.
He discussed several items, including how to build a 2 element yagi
antenna, and reported that little solar activity should be expected over the next few days.
I am a regular listener, and I especially enjoy Arnie Coro's Dx'ers
Unlimited show and the beautiful Cuban and Latin music that your station plays. I have been very pleased with the extended hours you are offering for your English service, staying on the air long after 0500 UTC. This gives me many more opportunities to enjoy Radio
Habana Cuba, as I often can't listen in until late at night.
If you have any QSL or verification cards, I would sure appreciate one memento of this occasion. If there are any other station collectibles you have available for your listeners,
I would appreciate anything you can send me! :)
I have an ICOM Communications receiver and an indoor mounted longwire antenna.
Hope to hear from you!Yours,

Sean Catney
Brampton, Ontario

Well amigo Sean, muchas gracias, thank you very much for the nice report and your comments about our new schedule, that has certainly helped many listeners to pick up the station at other times of the day... I hope that you keep listening to our programs and don't forget to send your valuable and much appreciated comments whenever you find something of interest.

Item three: Lots of feedback from the antenna topics section of the
weekend program that was dedicated to the very close spaced two element Yagi wire beam . Several listeners wrote asking for more
information , among other things, because as one of them commented, he could put up that type of antenna at his location pretty easily, and actually raise and lower it using pulleys without the need of any help from other persons, something that can't be done with a standard two element Yagi built using aluminum ube elements... So, after reading the e-mails, I decided to include in today's program some more information about the two element close spaced wire Yagi antenna...

Ready to copy .... here we go..

As regards to the 2 elements very close spaced YAGI antenna...
It is one of those "findings" that one makes while working with
sophisticated antenna modeling software, that, then happily you are able
to confirm in actual practice !!!

The "prototype" uses 0.1 spacing between a parasitic director element
and a half wave dipole element that is cut to the center of the
bandwidth you want to use. In my particular case the antenna was
designed for 20 meters band operation in the narrow segment
between 14050 and 14100 kiloHertz, with a center frequency of 14075...

It is a very sharp tuning antenna system, but provides the maximum
possible gain that can be achieved with a two elements Yagi.

The elements are made of 4 millimeters copper wire, and they are kept separated by three heavy duty thick wall PVC pipe spreaders ...

Just imagine a hammock without the canvas !!! and that's the way it looks

The input impedance at the center of the dipole element is very
low... between 8 and 10 ohms, depending on the height that the antenna is located above the ground ...

SO... I make the driven element a folded dipole, to multiple the
impedance by 4 times... Then the
antenna's impedance will be anywhere between 32 and 40 ohms...making it
possible to use it with
a balun transformer designed for 1 to 1 transformation...

The folded dipole element is balanced, and the coaxial 50 ohms feedline is unbalanced... You will end up with a voltage standing wave ratio of around 1.5 to 1 or a bit higher, quite usable with almost any amateur transceiver of even the most up to date design, and of course , perfectly accepted by the older vacuum tube transmitters !

I calculate the length of the half wave dipole by the formula 142.5/ f
mHz, and obtain the results in meters length of wire... and the director element is made 4 percent shorter than the length of the half wave dipole... Separation between the two wire elements is 0.1 wavelength at the operating frequency.

I have not actually measured the antenna gain as compared with a half wave dipole... but the sophisticated computer model "keeps insisting" that the gain of this parasitic director + half wave dipole system with 0.1 wavelength separation between elements provides a peak gain of 5 dB over the dipole at the same height above ground, and in actual practice, it seems to be true !!!

This " high gain two elements narrow band, low cost wire Yagi antenna " has been tested on 20 , 15 and 10 meters with excellent results, but I must tell you that IT IS NOT a broadband antenna. The one I built for 10 meters during the peak of solar cycle 23 was optimized for 28.495 kiloHertz the DX station's favorite spot, and I could move + and - about 50 kiloHertz without having to worry about the SWR going higher than 1.7 to one. The transceiver I was using had 2 X 6146's tubes in the final amplifier, so there was no problem at all with the SWR, as long as it kept below the 2 to 1 VSWR value.

My perception is that it is the ideal low cost antenna for PSK31 and
other digital modes that are concentrated around specific frequencies on the bands, like for example 14070
7070 etc...

Last but not least... I have never had any problems with this type of
low cost wire YAGI, except when the first one was built using bamboo poles as spreaders... the bamboo lasted about two years in our humid tropical climate... The white PVC schedule 40 heavy duty plumbers pipe , reinforced with a hard wood dowel and sealed at the
ends with epoxy will last a long time before ultraviolet light breaks the bonds of the polymer's chain of molecules.

AH... before I forget... I also made one for 6 meters and it worked very well too !!!
The 20 meters version, when used with an antenna tuner, can be operated up to the high end of the band, on 14325 kiloHertz , where the Hurricane Watch Net is active whenever a storm is in progress around our area.

Standby for more radio hobby related information, coming to you from Havana... I will be back in a few seconds after a short break for
station ID.

This is Radio Havana Cuba, the name of the show is Dxers Unlimited, and here is now our next item of this weekend edition...

Radio amateurs around the world invest a lot of time and efforts in
getting their stations ready for providing emergency communications
whenever they are required... A few weeks ago amateurs in Central
America and the Caribbean participated in a training exercise designed to demonstrate the capacity of stations operated by amateurs to pass emergency messages to a designated control station that in this case was located in San Salvador , the capital city of El Salvador . Several Cuban radio amateurs operated on the 40 meters band and were able not only to originate the test messages, but also to relay messages from stations located in other countries. The use of battery power and short antennas was also encouraged, in order to reproduce, as much as possible what would happen during an actual emergency. The International Amateur Radio Union organized the Global SET, or Global Simulated Emergency Test, and the results showed that many Region II Area C stations were
well prepared to provide their alternative communications services in
case of natural or man made disasters.

And now amigos, as always at the end of the show , here is your amigo Arnie Coro's HF plus low VHF band propagation update and
forecast... Four days without sunspots, the solar flux once again going back to the near 70 units mark... But, in contrast, the lower height of the F2 layer dring the local daytime hours has had a positive effect on the availability of the frequency spectrum from 15 to 22 megaHertz... bringing back to life both the 15 meters amateur band and the 13 meters international shortwave broadcast band. Expect an increase in the possibilities of sporadic E openings to
begin by the end of the first week of December... Don't forget to send your signal reports and comments about the program , plus your QSL requests...send mail to inforhc at enet dot cu... again inforhc at enet dot cu, and VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba