Dxers Unlimited10 – 11 Feb
Mid week edition
by Arnie Coro CO2KK
Hi amigos radioaficionados around the world ! Welcome to the mid week edition of Dxers Unlimited, your favorite radio hobby program...
The one and only attempting to cover all of the 84 ways that you and have the possibility of enjoying this wonderful way of using up your spare time. Sure, there are some of the that are really sophisticated, while others are as simple to implement at almost no cost, like AM broadcast band Dx using standard unmodified domestic consumer type radios ! As a matter of fact, AM band Dxing today has received quite a boost worldwide, thanks to the availability at very low cost of what can best be described as a new generation of lightweight , really portable receivers that use a radically different integrated circuit capable of extraordinary performance.
As a good friend of mine , who is a senior telecommunications engineer told me recently, the new Walkman type receivers, of which the Sony Model SRF-59 is the most well known example, make possible picking up amazingly far and weak AM broadcast stations, something that has created a new generation of AM Dxing fans....
They have set for themselves a strict set of rules,that include not using external antennas, that is, staying away from boosting the radio's performance by any external devices. But, not everyone is abiding by the rules, and just placing a Sony
Walkman SRF-59 near an external loop antenna brings in still more DX, as I was able to verify during a weekend daytime AM Dxing session.
More about AM medium wave broadcast band Dxing later in today's midweek edition of the program.
Item two: Radio amateurs are using free and open source software more and more, and there are several excellent programs for running the digital communications modes that are written specially for the LINUX open source operating systems.... Among those that have captured my attention is FLDIGI, a software that allows the radio amateur user to operate on practically all of the most popular digital communications mode, and that, as a free and open source program,is available at absolutely no cost.
FLDIGI, has a very nice looking graphical user interfase, and the learning curve is quite reasonable for anyone familiar with the use of computers.
Digital communications modes are becoming much more popular among the world's radio amateurs, because they provide excellent two way contacts while running low and very low powers and even during poor propagation conditions.
Si amigos, your radio or your computer is picking up Dxers Unlimited's mid week edition , and here is part two of today's feature dedicated AM broadcast band Dxing. Keeping a daily record of solar and geomagnetic activity is essential if you want to really enjoy Dxing stations that operate from 530 to 1700 kiloHertz...You must also keep in mind that AM broadcast band channels that are used in the Americas, that is ITU Region II, are spaced by 10 kiloHertz, while the other two world's ITU Regions I and III use a 9 kiloHertz channel separation. That difference is not relevant for users of analog AM receivers, but those using digital radios, do have to switch from 10 to 9 kiloHertz channel spacing when attempting to pick up the transatlantic or
transpacific AM stations,depending on your geographical location.
The presence of transatlantic stations when propagation conditions are very good is often detected by listening to the heterodynes or "whistles between channels" caused by the different channel separation in use by European and African stations, the most likely to be heard during periods of very low solar activity in the East Coast of North America and the Caribbean, when AM band Dxing is at its best ...
The extended period of very low solar activity that is considered by scientists as not typical to say the least, has prolonged the tail end of solar cycle 23 well beyond the classical 11.1 years average, and for that reason, low frequency propagation conditions have been very good for a much longer period than during the three last solar cycles.
Now here is item three: What can be done with an obsolete, but still in good working conditions laptop computer ? The very fast development of computer software that demands more and more machine resources like hard disk drive space, random access memory available and the CPU clock speed , has rendered as obsolete both desktop and laptop machines that still work well and may have a useful lifetime extending for several more years . So, radio amateurs that have already learned how to use different flavors of the LINUX operating system, have installed FLDIGI free and open source software and are using the old machines connected to their transceivers. It is interesting to underscore that the obsolete laptop machines are a much better choice for this application than the desktop computers, because the liquid crystal displays do not generate radio frequency noise , in contrast with the cathode ray tube monitors that cause lots of problems to the reception of weak signals because of the type of high voltage technology that they use.
Setting up the laptop computer to transceiver interfase is not a difficult task, but be aware that the best interfase systems make use of a device known as an OPTO-ISOLATOR , that provides extremely good protection of the computer serial or USB ports that are used to connect the transceiver to the laptop machine. You can certainly start to monitor the amateur bands for digital communications modes using a simple connecting cable, but the chances of running into trouble in case radio frequency energy leaks into the computer ports is extremely high... For receive only applications , a very simple connecting cable can be made in a few minutes, but if you want to transmit digital signals, please follow your amigo Arnie Coro's advice and learn about the fully optically isolated interphase systems, and build or buy one, before starting to transmit using the digital modes. Once your fully isolated interphase is installed and you are familiar with the FLDIGI software, you can start monitoring the ham band segments where the popular PSK31 digital mode is in use...
PSK31 is very easy to decode and you will see many ongoing two way contacts by just watching the waterfall display on the computer screen.
Yes amigos... don't keep that obsolete Pentium II or III laptop machine idle... Don't store it in a closet, or keep it inside a drawer... put it back to work for your enjoyment of the amazing amateur radio digital communications modes, that are capable of just unbelievable performance while running very low power from your transmitter...
This is the mid week edition of Dxers Unlimited, and just to give you an idea of the extremely quiet Sun, the last weekly report about solar activity speaks about a totally quiet Sun, with absolutely no sunspots for the whole week, and also no signs of possible active sunspot regions on the farside of the Sun.
Solar flux also at very low and absolutely steady level, so as a direct consequence, we are seeing a very weak ionosphere, with extremely low free electrons concentrations at the altitudes of the D, E and F regions.
Item five: A visit to my workshop... just taking a look at the ongoing projects and repair jobs... I am attempting to repair a Midland FM mobile 25 Watts transceiver that forms part of Anita and Ramon's ham radio station ...
Anita and Ramon are blind and they have found in the amateur radio hobby a very nice way of meeting new friends, and learning about communications modes. But they can not repair the broken down transceiver , so they must rely on the help provided by fellow hams for fixing their broken down equipment. The Midland set fried the audio output integrated circuit, and the original part is not available locally, so what I am doing, and about to finish , was to adapt another type of integrated circuit audio amplifier that can be found here at the TV set repair shops, and also I am adding a protection circuit, a very simple one, that will prevent the IC audio
amplifier from breaking down once again in case the loudspeaker is accidentally disconnected...
So soon CM3 AAR , Charlie Mike three Alpha Alpha Romeo, amiga Anita and CM3 RVG, Charlie Mike Three Romeo Victor Gulf, Ramon, by two very good blind amateur radio friends who live in the small town of Guines some forty miles away from Havana, will have their two meters base station back on the air...
By the way the very easy to implement protection against the accidental disconnection of the loudspeaker, can be easily implemented by anyone that owns radios using high power output audio amplifiers... It simply consists of soldering a fifteen ohms two Watts carbon resistor in parallel with the loudspeaker output terminals. I was able to find an empty area in the Midland FM transceiver, where the extra load resistor could be placed...In case the loudspeaker is disconnected , the fifteen ohms resistor is always there, placing a load at the output of the integrated circuit audio amplifier , thus preventing it from breaking down because of the lack of load.
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And now amigos ,as always at the end of the program, here is our exclusive and not copyrighted HF and low band VHF , 30 to 50 megaHertz, propagation update and forecast... Solar activity is expected to continue at extremely low levels, with the 10.7 centimeters wavelength solar flux staying below 70 units and the solar wind speed diminishing below the typical 350 to 400 kilometers per second and with a very low protons per cubic centimeter count. The propagation conditions on the frequency range above 15 megaHertz will be extremely poor... but the lower frequencies, in contrast will provide very nice DX windows, especially between 400 kiloHertz and three megaHertz...
Keep monitoring the low band TV channels and the segment between 30 and 50 megaHertz for any signs of possible sporadic E openings that are happening even during the usually very inactive for E skip month of February. Hope to have you listening to the weekend edition of Dxers Unlimited that will be on the air Saturday and Sunday UTC days, and don't forget to send your signal reports, comments about the program and radio hobby related questions to inforhc at enet dot cu or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana , Cuba.
