Mid week edition for 6-7 January 2009By Arnie Coro, CO2KK
Hi amigos radioaficionados around the world and in space !!! With our traditional salute, I am begining this mid week edition of Dxers Unlimited , that goes on the air when the Sun continues to be at a standstill, with absolutely no sunspots facing the Earth or on the farside of our nearest star.
Solar cycle 24 continues to dissapoint short wave enthusiasts and radio amateurs alike !!!
Item two: When short wave propagation is as bad as it is... you may want to explore the frequency range from 150 kiloHertz to 3 megaHertz. For example at higher latitudes, the transatlantic crossing is an almost nightly happening for several of the still on the air long wave AM broadcast stations. Canadian , American and Caribbean listeners are reporting picking up some really nice signals from Europe, Africa and the Middle East on the long wave band, that at this time of the year is easier on the ears, as the number of thunderstorms that cause static crashes is at a minimum.
Using a big multi-turn shielded loop antenna, you can enjoy excellent copy of some of the more powerful long wave stations, that, for example, here in Cuba start to come in as soon as the Sun sets, and are heard until sunrise at each of the station's locations. One of the very interesting characteristics of long wave reception is that signals are very stable, with slow fading rates, so you can actually listen to complete programs like newscasts without even loosing a single word to the rapid changes in propagation.
During extended periods of very low solar activity, like the one we are going through at this moment, the AM medium wave broadcast band is also in excellent shape, not only for Dxing , but for actually enjoying programs from far away places. I have listened here during the last week of 2008 and the first few days of 2009 to many AM DX stations from Puerto Rico, Mexico, Colombia, Haiti, Venezuela , but have missed the Dominican Republic, probably because the AM broadcast band stations in that Caribbean nation are not running the power output they used to have on the air during the days before the FM broadcast band took over most of the audience.
Using a simple multi-turn small loop, just 30 centimeters in diameter, I am able to tune stations that are operating in the same channel,separating them quite nicely by turning the loop around searching for a minimum signal from one of the stations on the same channel... Long wave and AM broadcast band Dxing are certainly a nice way to enjoy our hobby when the Sun is on vacations and there are no sunspots to boost the ionosphere making possible the propagation of higher frequency short wave signals, especially above fifteen megaHertz !!!
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This is Radio Havana Cuba, the name of the show is Dxers Unlimited, and of course that we doQSL, yes, we verify your reception reports, comments about our programs, and in the very special case of Dxers Unlimited, we also answer your radio hobby related questions, just as I am going to do right now, answering a questions sent by listener Carla from Salt Lake City , Utah.
Carla tells me in her e-mail sent to inforhc at enet dot cu, that she is enjoying AM broadcast band Dxing with what she describes as , and I quote “ an amazing pocket radio ”...Arnie, she says, I bought quite by chance a Sony Walkman AM-FM pocket receiver model SRF-59, and could not believe what I was hearing the last day of 2008 when a Cuban station...
Radio Progreso was its name, came in just as the Sun was setting at my location. The Sony SRF-59 has no loudspeaker, so you must wear earphones to listen to it, and that might help also, but after using it for several days and comparing what is heard on it and what can be picked up in my other Sony portable, an old IC 7600G, I thought immediately about sending a note to your program, and trying to learn more about this amazing small little pocket radio... Now , here is my answer to amiga Carla: Yes my friend, you are absolutely right, and I fully agree with you that the new integrated circuit design used in the SRF-59 pocket radio produces amazing results... The receiver is extremely sensitive and also is quite selective too, that meaning that it separates very well between stations. I also happen to have a Sony SRF-59 which was given to me as a very nice present by a long time friend, and the results achieved so far amiga Carla have proven to be really fantastic.
By coupling the SRF-59 to an AM broadcast band tuned loop, the receiver proved to be capable of picking up extremely weak signals ... It would be interesting to be able to obtain the integrated circuit as a stand alone electronic component and attempt to design an AM radio using better front end selectivity and possible a narrower IF filter... but then, the radio is no longer going to be a pocket receiver !!!
Yes amigos, si my friends, oui mes amis... the most recent Breakthrough of AM medium wave broadcast band Dxing was, without any doubts the launching of the ultra-compact pocket miniature receivers using the new integrated circuit technology... The Sony SRF-59 has just two integrated circuits, one is what we could best describe as the radio itself, the CX1129N propietary chip,and the other is just the audio amplifier module.
By adding an external tuned ferrite bar antenna, or a multi -turn tuned loop, it is possible to further increase the already amazing sensitivity of the SRF-59 Sony Walkman pocket receiver, something that I began to do the very same day that my radio arrived. By playing with the distance between the internal antenna and the external ones, it is possible not only to pick much weaker stations, but, also as I explained earlier, the possibility of picking up new stations by nulling out more powerful ones becomes an extra feature of the combined action of the two antennas, the one inside the radio, and the external one.
The current AM broadcast band DX season will last until the very early days of spring, so, you have enough time to get one of the new ultra light compact pocket receivers and add quite a number of new stations to your log. From Cuba, the easy ones should be Radio Rebelde, Radio Progreso, Radio Reloj, Radio Enciclopedia and several of the provincial networks, like Radio Guama, Radio Veintiseis,Radio W CMHW , Radio Surco and Radio Cadena Agramonte...
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This is Dxers Unlimited mid week edition, coming to you from Havana... and here is our next radio hobby related item amigos.... Poor propagation on the high frequency bands, especially from 10 megaHertz and up, but also hitting hard lower bands like 40 meters or 7 megaHertz, that traditionally were practically immune to the effects of the lower phase of solar cycles. Scientists are practically sure now that the extended periods of extremely low solar activity is the cause of what they are describing as a “ weak ionosphere”, that according to the propagation gurus is the cause to blame for the very poor propagation on the short wave bands... The year 2008 average number of sunspots was an amazingly low 4.3.... with practically three quarters of the days of 2008 without a single sunspot seen on the solar disc... Now , I am sure that you are going to ask two questions.... If and when this is going to change.... and sorry to say, all I can assure you is that YES, solar activity will sometime in the future is going to increase, but, it is practically impossible to forecast when solar cycle 24 is going to really start to enter its active phase !!!
Item five: A very popular section of Dxers Unlimited according to listener's correspondence... you are most welcome to the Technical Topics area of our show... Today, I am going to tell you more about ferrite rods, and Litz wire... the two item that are required to make your own AM broadcast band or Long Wave band ferrite bar antennas... All ferrite rods are not created equal, and as a matter of fact, the selection of the proper ferrite material for your homebrew antenna can make a lot of difference.
You can assemble a makeshift ferrite bar antenna using common enamel magnet wire, and a ferrite rod picked up from a broken down transistor radio, and YES, it would work, and it would certainly enhance reception of your portable receiver... but NO, it won't provide optimum performance...
Homebrewing a top quality, highly sensitive ferrite bar antenna requires the careful selection of the ferrite bar material, and using the expensive, hard to find, and harder to work with 11 slash 46 Litz wire... BUT, all the efforts devoted to finding the right type of ferrite bar, and obtaining the 11 slash 46 Litz wire, will be really worthwhile, as your homebrew antenna will be a top performer.
So good in fact, that it would help you to add a lot of new stations to your AM broadcast band station's log, and also, to be able to enjoy very nice reception of distant stations for the pleasure of listening to programs originating at a far away location.
And now amigos, as always at the end of Dxers Unlimited, when I am here in Havana and can make the whole set of solar and propagation observations required to prepare it, here is Arnie Coro's Dxers Unlimited's HF plus low band VHF propagation update and forecast...
Solar activity continues to be at very low levels... solar flux between 68 and 70 units, and we may see the effects of a high speed solar wind gust impacting on the Earth's magnetosphere by Thursday UTC day. The chances of sporadic E openings are diminishing as the winter solstice E skip season is coming to an end. Expect very good to excellent Dx conditions on long wave, medium wave and the tropical bands until the geomagnetic disturbance arrives. See you all at the weekend edition of the program amigos, Saturday and Sunday UTC days... and don't forget to send your radio hobby related questions, signal reports and comments about the show to inforhc at enet dot cu, or Via Air Mail to Arnie Coro, Radio Havana Cuba, Havana, Cuba
(Arnie Coro, Havana, Cuba via ODXA)