Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited's mid week edition for 2 -3 March 2010
By Arnie Coro
radio amateur CO2KK

Hi amigos radioaficionados , welcome to the mid week edition of your favorite radio hobby program, coming to you from sunny Havana, where cold air coming from the Arctic has sent the night time minimum temperatures to less than 10 degrees Celsius.... but that's only during the late evening hours, because as soon as the Sun rises above the horizon, our local temperature increases very fast indeed.

The high atmospheric pressure and dry air acts as a nice booster to enhance tropospheric ducting, so one can pick up amateur 2 meter band repeaters from very far away when this beyond the horizon signals appear locally.

Cuban radio amateurs have installed a large number of home brew 2 meter band repeaters, that have played a very important role during communications emergencies, providing very reliable back up to the professional commercial systems when hurricanes have struck our archipelago.

As I have said it here many times, one of the main reasons why the amateur radio service keeps its exclusive access to valuable areas of the HF , VHF and UHF radio frequency spectrum is precisely its outstanding capacity to provide instant, reliable and high quality communications links to and from disaster stricken areas.

The recent huge magnitude 8.8 earthquake that has caused so much loss of life and destruction of property in Chile is yet another example of how amateur radio operators always come forward and provide much needed communications, including the very socially important family relief services, helping to locate relatives in the affected areas...

Item two: The Sun continues to surprise heliophysicists, sunspots are growing out of nowhere suddenly and now we are seeing four active sunspot regions on the side of the solar sphere that we see from Earth.

They are not really very powerful or active, but, watching four solar active regions transiting the solar disc at the same time is something we had not seen in a long time amigos !!!

And that's not all, because on the side of the Sun that we don't see from Earth, but that now can be monitored by the Stereo pair of satellites, scientists are also watching other sunspot active regions that are developing.
Item three: A new digital communications mode for amateur radio communications created by a non-ham telecommunications engineer has created a lot of controversy among digital radio enthusiasts...

The discussions are centered around the fact that ROS, that is R O S, the name given to the new digital mode , seems to use spread spectrum technologies that are banned by many telecommunications administrations around the world that specify in their rules and regulations that spread spectrum can only be used, if at all, on frequencies in the UHF bands assigned to the amateur radio service.

In the meantime the now “old, but very reliable, easy to use and extremely popular PSK31 digital communications mode ”, continues to be the favorite one among the world radio amateur operators, that have learned how to use PSK31 even without a wired interface between the computer and the ham radio transceiver...

More about PSK31 , the easy mode, the easy way... later into the mid week edition of Dxers Unlimited, the radio hobby program that is always open to listeners around the world... Send your signal reports, comments about the show and radio hobby related questions to inforhc at enet dot cu.... again inforhc at enet dot cu, or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba.

In a few seconds, after a short break for station ID the program will continue... stay tuned !

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This is Radio Havana Cuba, the name of the show is Dxers Unlimited , and here is more about PSK31, the most popular digital communications mode , that has made possible amazing low power contacts around the world. As my good friend Jose Angel Amador, CO2JA , likes to say, PSK31 is not the best weak signal digital mode, but it has the virtue of simplicity on its side.

As a matter of fact, I have made it a point to demonstrate how PSK31 works to every visitor to CO2KK my amateur radio station...

The demo consists of finding a PSK31 transmission in progress, typically on 40 or 20 meters and just placing the computer's microphone close to the transceiver's loudspeaker, while using the excellent FlDIGI digital modes software.

To the amazement of my visitors , in a few seconds perfect text begins to show on the screen of the laptop or notebook computer... Then, I switch on the transceiver into the transmit mode and place the transceiver's microphone right next to one of the computer's loudspeakers and start calling CQ...

Yes amigos, you have heard it exactly as it is... PSK31 works extremely well without the need to use a physical hard wired connection between the computer and the transceiver. Using the acoustic coupling method, PSK31 works perfectly well...making it ideal for setting up emergency communications systems on the fly, when need comes.

Again, if you have a laptop or notebook computer to which the FLDIGI digital modes communications program is installed, then it will be very easy to learn first how to receive PSK31 signals on the HF bands, especially on the extremely popular 14.070 frequency on the 20 meters band that is very active all the time that 20 is open.

Item four: As the spring equinox approaches here in the Northern Hemisphere, the autumn equinox is also going to happen in the Southern Hemisphere... for a period of around 5 to 6 weeks, we all will be enjoying a nice HF bands propagation enhancement that happens twice yearly... centered around the third week of March, and the third week of September, when Planet Earth receives equal illumination from the Sun.

This equinoctial DX season is going to be the last one that will provide really good AM medium wave broadcast band propagation conditions, because as solar cycle 24 continues its upward swing, ionospheric absorption will increase to levels that will severely limit the AM band DX possibilities.

So, if you want to add a few new ones to the AM broadcast band stations logged, this is your last chance in around five to six years to enjoy low ionospheric absorption , something that only happens during periods of very low solar activity.

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Si amigos, you are listening to the mid week edition of Dxers Unlimited, coming to you from Havana, I am Arnie Coro, radio amateur CO2KK, and here is item five of today's program...Things found during the big move of my shack to the big garage...

Roxana my wife is also a radio amateur, her callsign is CL2ROX, and soon she will be taking the test to upgrade to a second class license, that will allow her to operate on the short wave bands … with her third class license, the one she holds now, it is possible for her to operate on a segment of 160 meters , with just 10 watts, and also on a segment of 2 meters, again limited to 10 Watts... but if she passes the test, the second class Cuban amateur radio license will make possible for her to operate with up to 500 Watts input power and on almost all the HF bands.

This is a great incentive to upgrade, and that's why when we decided to move my shack and workshop from one of the bedrooms of our apartment to the big garage, Roxana asked me to install the our HF station in a nice oak table that is now in our bedroom. That requires that the new station be installed properly, no wires hanging, no experimental setups … you understand … right ?

So all the experiments have to be done, from now on, at the garage shack ….

After the move is completed, Claudia our 5 years old girl will have her own bedroom in what was until now my shack and workshop...

And now, here is ,the rest of the story... while starting the BIG MOVE, I have found a lot of things that I even didn't remember that they were in storage … so, many new projects will be possible in the near future, not only for my own ham radio station, but also for the benefit of many of my radio club members, that are now , like Roxana, passing the second class amateur radio license test.

Among the projects that will be possible to implement is a Polyakov direct conversion receiver that requires high quality computer high speed switching diodes... that fortunately were found deep inside the bedroom's closet where I kept the electronic components in long time storage...

A plastic bag with stamped 50 IN4148 diodes, will make possible to build at least 20 new 40 meters band direct conversion receivers, and keep 10 spare ones , for other projects.

Si amigos, yes my friends, oui mes amis, when you have spent your whole life enjoying the radio hobby, it is quite common to forget where you stored electronic components thinking about future projects... The plastic bag full of 1N4148 computer switching diodes is a good example of what I am talking about... and by the way, another plastic zip lock bag full of BC177 PNP silicon small signal transistors was also found behing one of the drawers when the move to the garage began.

That new finding led to a search for the specifications of the BC177's, and yes, they can be also be used for the Polyakov harmonic mixer direct conversion receiver project... Add to the IN4148 diodes and the BC177 transistors a carton full of circuit boards from broken down electronic fluorescent light bulbs, and as you can guess, we can prepare a nice receiver parts kit .

Home brewing simple receivers is a lot of fun, and the performance that you can expect from a well built Polyakov direct conversion receiver equipped with a set of well designed audio filters is really amazing amigos.

I build them using a sharply tuned filter for CW reception and a bandpass or lowpass filter for receiving single sideband voice or digital mode signals .

The most difficult part of this receiver is the variable frequency oscillator or VFO , but don't worry, I will be talking about how to make a nice VFO in a future edition of Dxers Unlimited amigos !!!

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 flux is near 80 and is expected to increase all along the week, the number of sunspots has increase to 39 , according to the Catania solar observatory's optical observations.

Expect nice openings on the 20 meters band from local sunrise to about two hours before noon and from about four PM local time until about an hour or two after local sunset.

There are good chances also of 17 and 15 meters band openings, and the 16 meters or 18 megaHertz international short wave broadcast band is going to be the best during the local daylight hours .At night your local time the best bands will be 19 and 22 meters just after sunset, shifting later to the 25 and 31 meters band during the late evening. The 6 and 7 megaHertz bands will be good also after about 9 pm your local time and until very early in the morning..

I don't expect high probabilities of sporadic E openings...so we must wait until the end of April for the spring -summer sporadic E season to begin. Dont' forget to send me your signal reports and comments about the program as well as any radio hobby related questions you may want to ask...send e-mail to inforhc at enet dot cu or VIA AIR MAIL , send a postcard or letter to Arnie Coro, Radio Havana Cuba, Havana, Cuba.