Dxers Unlimited weekend editions
by Prof. Arnaldo Coro Antich
radio amateur CO2KK
Radio Habana Cuba
Radio Havana Cuba
Hi amigos radioaficionados around the world and in space ! You are now listening to the mid week edition of Dxers Unlimited, your favorite radio hobby program. I am Arnie Coro, radio amateur CO2KK, your host here in Havana, and here is item one:
Solar cycle 24 is now well into its long delayed
startup phase, with daily solar flux figures that are providing much
better HF bands propagation conditions all around the world.
Just to give you an example... the 21 megaHertz or 15 meters amateur band is now opening from very early in the morning local time until late in the afternoon, making possible excellent DX contacts while running a 100 Watts power transceiver and a wire antenna.
In other words, a radio amateur that owns and operates the typical short wave station will be able to make contacts with similar stations half way around the world at some specific moments of the day when propagation conditions peak.
The example I have just mentioned follows... it was about ten minutes to six o'clock in the afternoon local time here in Havana on Monday ... I was tuning around the 15 meters or 21 megaHertz band when a very nice signal was heard . it was very near 21 300 kilo Hertz and he was running what is known among radio amateurs as a pile up, that meaning that a lot of stations were calling him.
His station's prefix, KH7, told me that he was located in Hawaii... I tuned my ham radio transceiver just 10 kilo Hertz down from his frequency , and then went back to his frequency, waiting for him to call again QRZ, asking for more calls.
Well, my recently installed G5RV multi-band dipole did a good job, and KH7HI, kilo hotel seven hotel india, Peter, came back to my call with a very nice signal report.
We had a short contact, but nevertheless had the opportunity to share our points of view regarding the much improved propagation conditions.
The QSO, or two way ham radio contact happened when
here in Havana the Sun was still way above the horizon, indicating a
very active F2 layer of the ionosphere....
Item two... also amateur radio related, and that qualifies as yet another amazing achievement regarding the use of extremely low power stations .
AA1TJ, my good friend Michael, carefully measured the power output of his 20 meters band transceiver down to the just 10 milliWatts, that is 10 thousandths of a Watt... connected the rig to his antenna and started to look for possible CW or Morse Code radiotelegraphy contacts...
Amazing as it may sound, and related of course to the much improved short wave bands propagation conditions, AA1TJ was able to make a two way contact with France, and another one with a station located in the Caribbean island of Martinique.
Now, you can plot the distance on your map between Mike's station located in Roxbury, Vermont, a New England USA state ,and his contacts in France and Martinique.
Here is now how Mike, AA1TJ describes his Monday March 15th two DX contacts running an extremely low power or QRP sub p transmitter ...
Now I quote , as Mike tells in his e-mail to the QRP-L Internet list: “I called 20m CW stations for most of the afternoon with my Bell Ringer transceiver. It normally puts out 1.5w of RF output power but today I dropped it down to 10mW.
The first couple of hours were slim pickins; I had a
"SRI OM TOO WK from one NA station and then
I had strong European stations fixed in my cross hairs
at least a half-dozen times; the perfect
"CONGRATULATION FOR 10 mw !!
Mike ends his e-mail opening up the possibility of running just ONE MILLIWATT or one thousandths of a WATT and attempting to make two way ham radio contacts with that extremely low power transmitter...
Yes amigos, si my friends, oui mes amis... as the short wave bands propagation conditions continue to improve due to the increase in solar activity, I am sure that many excellent QRP or low power amateur radio two way contacts are going to be made by those who accept the challenge of running their stations at really minimal power settings...
Stay right here on this frequency or keep that world wide web connection with us, as Dxers Unlimited's mid week edition will continue in just a few seconds ,after a short break for station ID... I am your host Arnie Coro, radio amateur CO2KK in sunny Havana...
You are listening to Radio Havana Cuba, the name of the show is Dxers Unlimited, and here is now our next item of today's program... YOU have questions and Arnie tries to answer them, la NUMERO UNO, the number one most popular section of the show.
Today I will be answering a question sent by several newcomers to the amateur radio hobby... They all want to know more about how to build and install a simple antenna for working DX on the ham bands from 20 to 10 meters.
This is a quite logical question, because at this moment, as it happens always at the start up phase of a new solar cycle, those of you who have never before heard DX stations on the 20, 17, 15, 12 and 10 meter bands, are astonished when those rare prefixes from halfway around the world start to come in , while you are using a low frequency antenna.
Also, as usual, all attempts to make two way contacts with those stations , almost always end in disappointing failures, because the low frequency antennas, although they may be operated using an antenna tuner, don't have the adequate vertical radiation pattern to make possible the long distance contacts.
Amigo Gabriel from Mexico, together with amigo Frank from Canada and amigo Bruce from Australia are all newcomers to the short wave amateur bands, that are going now through that unique experience of hearing stations on the five higher HF ham bands, while , as they tell me in their e-mail messages,here is what Bruce had to say:
“ Arnie, it is next to impossible to work those DX stations using the 40 meters band half way dipole antenna “ , and something quite similar was sent by amigo Frank. who also added in his e-mail that he had heard that the 40 meters band antenna could be used on 15 meters too...
Well, here is my answer amigos... if you want to really start working DX stations , my advice is to build a half square antenna for the 17 meters band, that has proven to work quite well also on 15 and 20 meters, when operated with an antenna tuner..
The half square is a low angle radiator, so the signals launched from it will hit the F2 layer of the ionosphere during the local daylight hours at the best possible angle to make possible DX contacts.
If your transceiver doesn't have the capability of working on the 17 meters band, as most of the older radios , then make the half square for 15 meters , that at this moment is the best band to work DX while running power outputs of 100 watts or less.
Yes you heard it right amigos, according to geosciences experts that follow the evolution of the Earth's ionosphere during this phase of the solar cycle, the best band for Dxing at this moment is 15 meters, closely followed by 17 meters.
All I can say is that a very simple, low cost and easy to build half square antenna for the 15 meters band will make possible excellent DX contacts, and it you have enough space to install two of these antennas at a 90 degrees angle from each other, and provide the possibility of switching between them , then you are going to be the proud owner of the lowest cost DX antenna system for the 15 and 17 meter bands.
Again, where at this particular moment of the solar cycle , your chances for working DX stations are the highest...
The half square antenna is just a pair of quarter wave vertical fed in phase by means of a unique single wire transmission line phasing section.
It won't use a lot of physical space, and the matching of the antenna system to the 50 ohms coaxial cable downlead is excellent.
According to my own measurements on the many half square antennas that I have built here for the amateur bands between 2 meters and 20 meters, if you follow closely the calculated design parameters, the half square antenna's feedpoint impedance will show up to be very near 50 ohms... actually, and depending on the surrounding objects, the resistive component of the antenna's impedance will be around 43 to 45 ohms, and the antenna's reactance will show a very low value, so low in fact, that there will be no need at all to use an antenna tuner, once the half square antenna is trimmed for maximum efficiency at the center of the 15 meters band
Just to give you an idea of what I am talking about, the 15 meters band half square antenna will need no more than 10 meters horizontal space for its installation, and this is considering that you are going to leave about one and a half meters to separate the antenna vertical wire elements from the supporting masts towers or trees.
The antenna doesn't need to be to high above the ground or rooftop to be very effective... As a matter of fact you will need the supporting structure to be no more than 9 meters high to install a 15 and 17 meters band half square antenna...
My 15 meters half square design shows a standing wave ratio of just 1.15 to 1 on 21250 kiloHertz, and when used on 17 meters, a very simple L type antenna tuner makes possible to achieve also an almost perfect SWR. On 17 meters the antenna gain will be slightly less than on 15 meters, but it will be hard to notice when the band is really open.
I have yet to test the antenna on the 12 meters band, something I am planning to do as soon as possible.... If you want to know more about the HALF SQUARE dual band DX antenna for the 15 and 17 meters amateur bands, just send an e-mail to inforhc at enet dot cu, again inforhc at enet dot cu.... or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba.
And now as always at the end of the show here is Arnie Coro's Dxers Unlimited's HF plus low band VHF propagation forecast....
Transequatorial propagation season is just beginning here in the Northern Hemisphere.
I have already heard several Argentinean 6 meter band stations , at the time that TEP propagation peaks here in Cuba, that is just after my local sunset and for the next three hours.
Solar activity is expected to stay at low to very low levels, with just one now decaying solar active region on sight.
Solar flux is around 85 units, the sunspot number is at around 28 but it should increase when a new sunspot group rotates into view. Expect good Dx conditions on 15 meters between 10 AM and 6 PM your local time... while 20 meters will stay open much later into the evening now that we are approaching the spring equinox. See you all at the weekend edition of the program amigos... on the air next Saturday and Sunday UTC days on this same short wave frequencies and from our www.radiohc.cu website streaming audio...