Radio Havana Cuba Dxers Unlimited Dxers Unlimited’s week end edition for 26-27 May 2007 Hi amigos radioaficionados , around the world and in space… I am Arnaldo, Arnie, Coro, radio amateur CO2KK your host at this twice RHC program devoted entirely to the promotion and development of our wonderful and fascinating hobby, the ever changing and always challenging RADIO. Let’s begin this program with a news item about the forecasting of magnetic storm, in my opinion a very significant breakthrough in solar physics and the vitally important relation of our homus sapiens species with the Solar System… A scientist using the Solar and Heliospheric Observatory (SOHO) has found a way to forecast solar radiation storms. The new method offers as much as one hour advance warning, giving astronauts’ time to seek shelter and also ground controllers time to safeguard their satellites when a storm is approaching. As many of Dxers Unlimited listeners have heard here, more than one telecommunications satellite has died when a strong magnetic storm has sent heavy ions into the critical areas of the spacecraft, damaging vital control circuits.
"Solar radiation storms are notoriously difficult to predict—they often take us by surprise," says physicist Arik Posner who developed the technique. "But now we've found a way to anticipate these events.", he added in a Friday press release. Posner is a member of the research staff of the Southwest Research Institute in San Antonio, Texas USA and he also works at NASA Headquarters in Washington, DC. His study, titled “Up to one-Hour Forecasting of Radiation Hazards from Solar Energetic Ion Events” is published in the specialized scientific journal Space Weather. The early warning of magnetic storms will also provide some interesting possibilities for amateur radio operators at high latitudes, as they may get ready to make some nice DX contacts via aurora borealis propagation that is usually associated with the solar magnetic storms. Item two: Also related to solar activity… once again after a brief, really short period of enhanced activity, the Sun is back to the typical levels of solar flux that are experienced during solar cycle minimum… Flux levels of around 70 units, very close to the minimum baseline activity are now in progress. Item three: The very low solar activity combined with the summer thermal expansion of the ionosphere has sent the daytime maximum useable frequency curve as low as it can go… and again, we are watching how once the Sun sets, a very interesting increase in the maximum useable frequency on some circuits takes place, providing a relatively short period of enhanced propagation conditions. Item four: Still another compact antenna is making headlines, the TAK-TENNA a dipole, makes use of two spiral wound loading coils at the ends of the very short elements, providing both inductive and capacitive loading…More about the TAK-TENNA in this weekend edition of Dxers Unlimited that will continue in a few seconds, after a short station ID… I am Arnie Coro in Havana… ……. This is Radio Havana Cuba, the name of the show is Dxers Unlimited and you can pick it up twice in the week, on Tuesdays and Wednesdays , our mid week edition, and on Saturdays and Sundays our weekend edition, the one you are listening to at this moment… Now, as promised earlier, here are some comments about the latest newcomer to the long list of amateur radio compact antennas, the TAK –TENNA, that uses a time proven and effective way of making a very short antenna that is still able to provide a rather reasonable radiation efficiency. The TAK-TENNA consists of a heavy and well built center insulator, two short braces made of aluminum tubing and at the ends of each of them a wire spiral that acts as an inductive and capacitive loading that makes the very short antenna resonate to the amateur band for which it is designed. The 40 meter model is so compact that it can be installed in a very small space, making possible to operate on that band that has become much more popular now that the solar cycle is at its very bottom. In order to better understand how it works, I built from scratch a 10 meter band model of the TAK-Tenna, using PVC pipe cross braces to keep the one quarter wavelength of wire spirals in position. The antenna is amazingly small, and it was possible to adjust it with the standing wave ratio meter for resonance on 28.4 megaHertz, while obtaining a rather nice low SWR from 28.0 to 28.8 megaHertz . Finding the correct setting for the wires that connect the aluminum legs of the antenna to the wire spirals wasn’t easy, but finally I ended up finding the right spot. I used number 14 bare copper wire for the spirals that were made with a total length of two and a half meters wound into a spiral with a diameter of 50 centimeters. Another experiment used a still smaller diameter spiral, but keeping the same quarter wavelength of wire to form the spiral. As with any half wave resonant dipole antenna, the TAK-TENNA proved to have a rather sharp bi-directional horizontal pattern, so it was very easy to find a setting of the antenna that produced the minimum noise from my next door neighbors extremely noisy computer an monitor, something that could not be done with a fixed half wave wire dipole. Now, I must look for the proper materials, and build a pair of these antennas, one for 10 meters and the other one for the number one favorite DX band, 20 meters, Before I forget, I used a simple coaxial cable choke balun right at the feed point and had no problems with parasitic RF currents at power levels of up to 200 Watts. Small antennas are always coming into the attention of radio amateur magazine editors because for HF operation the size of the antenna is a limiting factor for many operators that can not work on HF with standard size antennas. ……….. ASK ARNIE, si, amigos, sure, you can send your radio hobby related questions to ASK ARNIE, la numero uno , the most popular section of Dxers Unlimited… Here is today’s question sent to ASK ARNIE, by listener Gabriel in Delaware , USA, and also answering a very similar question that came from Desmond in the UK… So amigo Gabe and Des, here is the question followed by my answer: Question… Arnie can you recommend a particular antenna design for someone that has a very small space available to install a short wave receiving and transmitting antenna? ANSWER: Amigos Gabe and Des my advice is to review the possibilities of using , for example, a flagpole antenna if it is possible to install a flagpole at your QTHs… A second option would be to explore the use of a compact short antenna that uses efficient loading, and a third one , that is becoming more and popular around the world, would be to use a magnetic loop antenna, that in the case of a receive only installation is very easy to homebrew, will cost practically nothing and also will prove to be highly effective in making better reception possible in high man made noise areas. The problem with a magnetic loop capable of transmitting is the extremely high voltages that even a low power transmitter will generate in the form of single or two turn coil type antennas, which can reach several thousand volts!!! I regularly used with my bedside HF regenerative receiver an untuned short inverted L antenna, that provides very good reception on frequencies between 2 and 18 megaHertz, while at the same time making possible to listen to local and semi-local AM medium wave band broadcast stations. The short inverted L is an option that may also be considered, and with a ground counterpoise it can be used for transmitting on the amateur bands from 10 megaHertz up, although its performance won’t be amazing as you can expect from a length of wire that is less than a quarter wavelength on the 30 meters band…. My inverted L is just five and half meters long, with about three meters moving up into the mast and the rest placed in a horizontal position . The wire that acts as a counterpoise is six meters long, and by using a homebrew multi-tap loading coil, I have used this antenna to transmit on 40 meters for local contacts too!!! Amigos Des and Gabe, as you have just heard, there are many possible options to install HF antennas when you are very short of space, and I must add that it is a lot of fun to install different antennas and compare results, before settling down, as I did with my modest, yet efficient inverted L….that has allowed me to make many nice DX contacts on the 20, 17, 15 and 10 meter bands, despite the very low solar activity at this moment. ……. Visit my workshop, join me for a tour of my workbench, where an old Pentium II motherboard was installed to a well preserved AT machine case, and provided with the LINUX operating system. The computer is now under test using software written for LINUX that allows working the now very popular PSK31 keyboard to keyboard communications mode. So far the rather slow by today standards 333 megaHertz CPU , an INTEL Mendocino , is letting me pick up many PSK31 stations on the 20 meters band , centering my scan on 14.070 kilohertz… I have now to install the permanent interface between both, one of my HF transceivers, a VHF two meters band rig and the just revived Pentium II machine, in order to start working PSK31 on 20 meters on a regular basis, something that I want to be doing in the very near future. So those of you that are amateur radio operators and have already tested your stations using PSK31, be on the lookout for a two way QSO with a guaranteed QSL with CO2KK amigos!!! And now as always at the end of the program, when I am here in Havana, this is Arnie Coro’s Dxers Unlimited HF plus low band VHF propagation update and forecast. Solar activity again at extremely low levels … solar flux at rock bottom 70 flux units …actually the forecast for solar flux values through the end of the month of 70, 70, 65, 65, 65, 70 and 70 for May 25-31. When the sun spotless for extended periods, we often sees solar flux values below 70, so a prediction of a solar flux of 65 implies no sunspots. The three lowest solar flux values I am aware of were between July 19-22, 1996, at the bottom of solar cycle 22, when they were 64.9, 66.1, 65.4 and 65.1. There you have it, the lowest, second lowest and third lowest solar flux values, all during those four days of 1996. This extremely low solar activity has sent the daytime maximum useable frequency curve into a nose dive, with only brief periods of good propagation at frequencies above 20 megaHertz. High probabilities of Sporadic E openings are still very much present, with an increase to happen by the end of the month as we enter into June, the month of the year that shows the highest number of Sporadic E events. Hope to have you all listening to our mid week edition next Tuesday and Wednesday amigos, and don’t forget to send your signal reports and comments to [EMAIL PROTECTED] or VIA AIR MAIL send a post card or letter to Arnie Coro, Radio Havana Cuba, Havana, Cuba ---[Start Commercial]--------------------- Preorder your WRTH 2007: http://www.hard-core-dx.com/redirect2.php?id=wrth2007 ---[End Commercial]----------------------- ________________________________________ Hard-Core-DX mailing list Hard-Core-DX@hard-core-dx.com http://montreal.kotalampi.com/mailman/listinfo/hard-core-dx http://www.hard-core-dx.com/ _______________________________________________ THE INFORMATION IN THIS ARTICLE IS FREE. 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