Dxers Unlimited Saturday, April 25, 2009 Dxers Unlimited weekend edition 25-26 April 2009 Radio Havana Cuba Dxers Unlimited Dxers Unlimited's weekend edition for 25-26 April 2009 By Arnie Coro radio amateur CO2KK Hi amigos radioaficionados around the world... big hello to all three million PLUS of you nice people that like me enjoy this wonderful hobby a lot ! Welcome to the weekend edition of your favorite radio hobby program, coming to you via short wave and also from 05 to 07 UTC as part of our streaming audio from www.radiohc.cu. Here is now our first news item... one lonely sunspot, , yes, a small lonely short living sunspot, that according to scientists belonged to solar cycle 24 broke the 25 days in a row of ZERO sunspots, but it vanished after just a very short existence. Some heliophysicists are optimistic after seeing that minute sunspot, while others are not ... In the meantime, we continue to watch , and the extended tail end of cycle 23 continues to dominate solar inactivity. Item two: Sporadic E is here, and it came a bit earlier than usual... reports from many dyed in the wool 10 meters band operators confirm E skip openings at such odd hours as 10 or 11 pM local time. I also realized that a sporadic E layer was overhead of my station while working on 40 meters and having two way contacts with stations located just 50 to 200 miles away in the evening, something that can only happen if there is a sporadic E cloud right overhead. Item three: Have you ever heard of Class E radio frequency amplifiers ?. If not, it is about time to do an Internet search engine exploration and find out about that type of super high efficiency amplifiers, that will boost your signal tremendously while using minimum energy from the power supply. But NO, those Class E amplifiers are not LINEAR, so they can only amplify a constant carrier... nevertheless they are an excellent choice for operating CW under battery power. Item four: The StingRay 65 antenna for 2 meter band handie talkies will boost both your transmission and reception at very low cost, as you can homebrew it from half of a TV rabbit's ears antenna and the connector used by your HT , plus a bit of epoxy resin and the usual dose of ham radio ingenuity !. Si amigos, there are more than 84 ways of enjoying this wonderful hobby, and here at Dxers Unlimited you will always be learning something new...be it how to build and install your own backyard radio telescope to pick up Jupiter's radio signals ,or assembling a simple one diode, plus one transistor and one integrated circuit receiver that will be featured here today in our technical topics section. Keep listening to Radio Havana Cuba, as Dxers Unlimited continues in just a few seconds... ............. Si amigos, you are listening to the weekend edition of your favorite radio hobby program, Dxers Unlimited with yours truly Arnie Coro... and here is as promised earlier our technical topics section.... The One Plus One Plus One short wave receiver... a unique very simple project that can be built during a few hours of your spare time... I will start by describing this direct conversion receiver . The name comes from the fact that it uses one signal diode, one transistor and one integrated circuit. So that's why I have named it the One Plus One Plus One short wave radio. This receiver does need an external antenna . The input circuit is formed by a simple resistive attenuator, and a dual tuned bandpass input circuit , to which a signal diode is connected. The signal diode acts as an ultra simple product detector, when it is also fed with radio frequency energy coming from the one transistor local oscillator. At the output of the mixer we have audio from the station that we want to pick up, and it is fed to the integrated circuit audio frequency amplifier. This is a barebones receiver by all engineering standards, but it is really amazing how nicely it works when connected to an external antenna ! My prototype's signal mixer product detector diode was changed several times, in order to determine which type provided the best performance, and I must say that the 1N914 and IN4148 series proved to be excellent, with other types of diodes also working OK. I even tested a super high performance microwave diode, and at the other end, a type 1N34A that was built more than 55 years ago ! The most critical circuit of this One Plus One Plus One short wave receiver is the local oscillator, because it must be very stable in order for to receiver to work properly. As a matter of fact, one of the tests that worked very well was to use a quartz crystal to control the oscillator's frequency. I happened to have an exactly 6 megaHertz frequency crystal, and using it the One Plus One Plus One , I am able to receive our own Radio Havana Cuba's transmitter that operates on that frequency. The frequency of the quartz crystal must be set exactly to six dot zero , zero, zero, zero, in order to be able to receive in the so called exalted carrier mode , that requires an ultra exact local oscillator frequency. The experiment proved to be very interesting, as our transmitter's operating frequency is kept within plus or minus two to three cycles per second, because we use a very sophisticated frequency synthetizer. During the local morning hours here in Havana when we use the 6000 kiloHertz frequency to broadcast the Despertar con Cuba program in Spanish, I was able to keep the One Plus One Plus One fully synchronized with the transmitter so the audio coming out of the loudspeaker was of excellent quality. Replacing the crystal controlled oscillator with a field effect transistor variable local oscillator , it was possible to pick many stations on the 40 meters amateur band, using CW and single side band voice modes, and I could also hear the digital modes, easily recognized around 7070 kiloHertz. When one of the local radio amateur visited my workshop recently and saw the breadboard version of the One Plus One Plus One, he asked how it could be further improved, and that started a long analysis about how direct conversion receivers can be optimized, that lasted more than two hours. At the end of the conversation he left with one of my hombrew double balanced mixers, a pair of field effect transistors a low noise audio transistor and a type LM380 integrated circuit audio amplifier, that he soon interconnected producing a very nice performing direct conversion receiver, that as expected is much more complex than the ultra simple One Plus One Plus One radio from which he picked up the design concept. You can learn more about the One Plus One Plus One direct conversion short wave receiver, by sending an e-mail to [email protected], with the request for the One Plus One Plus One direct conversion receiver files ... .......... Si amigos, yes my friends, oui mes amis... the spring and summer Sporadic E season seems to be already in progress, and 10 meter band operators where the first one to find out about the presence of those elusive patches of very high ionization that move fast at altitudes of between one hundred and one hundred and fifty kilometers above the Earth. One way of knowing that a sporadic E propagation event is in progress is by monitoring the segment of the ten meters amateur band that is used by beacon stations, that transmit automatic Morse Code identification of their callsigns and locations. Those of you that own amateur transceivers with a scanning function, can simply set the low end of the scan fro 28.1 and the high end to 28. 5, so as to maximize the probability of finding activity of the band, not only from the beacons, but also from hams that operate digital and single side band voice modes from 28.1 to 28.5 . When the 10 meters band is open by means of the sporadic E skip , the distance that can be reached is shorter than when the band opens via the much higher altitude F2 layer , but anyway, it is certainly nice to hear the band open for DX ! Now our next item, also related to the already in progress E skip signal, this time it has to do with TV and FM broadcast band DX... TV DX from stations located in the United States of America will change totally when the analog blackout takes over, and only digital TV signals will be on the air from the USA. TV Dxers that already are learning about digital TV from far away locations , have told me that the digital signals are not as enjoyable to watch because of the very nature of the transmission mode. The digital TV signals are seen OK maybe for a while, then the picture freezes up, then it just vanishes, and there is no intermediate condition... in other words, it is quite different from analog signals that slowly fade in and out, without those on and off switching that is present with the digital TV DX. FM broadcast band Dxers will continue to enjoy the analog stereo the way it is, but in the future a new FM band broadcast standard may replace it, something that like in the case of digital TV will require totally different new receivers. ....................... ASK ARNIE, is now tied up with the HF propagation update and solar activity report as the number one most popular section of the program... according to the e-mail messages sent to inforhc at enet dot cu, or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba . Here is ASK ARNIE today, with a question sent by listener Vladia from Russia. Vladia picks up our 6000 kiloHertz English language program when we are broadcasting to North America,the signal travels over the North Pole and reaches Vladia's home QTH from 05 to 07 UTC !!! Vladia wants to know why our signals on that band are stronger during certain part of the year , and are much more difficult to pick up at another times. She refers that the periods around the spring and autumn equinoctial seasons, when signals are much better than during the summer season. She also explains that during the winter season, signals of our 6000 kiloHertz frequency can be picked up much earlier in the evening her local time, but the signals are not as strong as during the spring and autumn seasons. The answer to your question amiga Vladia, is that the ionosphere goes through several seasonal changes that are especially seen on very long range propagation of radio signals. And I must add that running 250 kiloWatts to an almost 20 decibels gain antenna, does help to enhance the reception at very long distances. And now amigos, here is our Dxer Unlimited's HF plus low band VHF propagation update and forecast, that also includes a solar activity report to help you plan your short wave listening and amateur radio activities... Solar activity once again back to extremely low levels, after the very short life of the high latitude sunspot of cycle's 24 magnetic polarity. The E skip season is now picking up, and that may lead to some nice short skip contacts on 20 meters, plus longer range QSO's on the 10 and 6 meter bands. Expect a fast drop in the maximum useable frequency about two hours after sunset your local time... with the later arriving signals coming from the West and Northwest of your location. Send your signal reports and comments about the program to [email protected] or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana Cuba Posted by Arnaldo Coro at 9:49 PM Labels: Dxers Unlimited 25-26 April ---[Start Commercial]--------------------- Order your WRTH 2009: http://www.hard-core-dx.com/redirect2.php?id=wrth2009 ---[End Commercial]----------------------- ________________________________________ Hard-Core-DX mailing list [email protected] http://montreal.kotalampi.com/mailman/listinfo/hard-core-dx http://www.hard-core-dx.com/ _______________________________________________ THE INFORMATION IN THIS ARTICLE IS FREE. It may be copied, distributed and/or modified under the conditions set down in the Design Science License published by Michael Stutz at http://www.gnu.org/licenses/dsl.html
