Sunday, January 06, 2008

Dxers Unlimited's weekend edition 5-6 January 2008

Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited’s weekend edition 5-6 January 2008
By Arnie CoroRadio
amateur CO2KK

Hi amigos radioaficionados around the world and in space… welcome to the weekend edition of Dxers Unlimited coming to you from Havana . I am Arnie Coro, radio amateur CO2KK , and it is my pleasure to begin another year during which Dxers Unlimited will be on the air, as always at the service of radio hobby enthusiasts , people like you and I who enjoy this wonderful way of spending our spare time.Now here is our first item of today’s program, it’s certainly very important news, that I am sure is going to make everyone really happy…
It’s news we were all waiting for ansiously… finally, it has happened, 93 million miles away from Earth, the long awaited first reverse magnetic polarity high latitude sunspot group has appeared, signaling the start of solar cycle 24 !!!Yes amigos, the Sun made headlines asSOLAR CYCLE 24 BEGINS: Solar physicists have been waiting for the appearance of a reversed-polarity sunspot to signal the start of the next solar cycle. The wait is over. January the third a magnetically reversed sunspot emerged at solar latitude 30 N,, and that amigos is what we were all waiting for …this is an almost one hundred percent assurance that the new cycle has now started, but let me add that the solar maximum for this new cycle is still several years away…The magnetic configuration of bipolar sunspots with leading positive/negative polarity in the northern/southern hemisphere, is associated with solar cycle 23. According to what is known as the butterfly rule, the new high latitude sunspot region belongs to cycle 24. It was named active region 10981 or just 981 for all practical purposes.New solar cycles always begin with a high-latitude, reversed polarity sunspot, according to solar scientists."Reversed magnetic polarity " means a sunspot with opposite magnetic polarity compared to sunspots from the previous solar cycle. "High-latitude" refers to the sun's grid of latitude and longitude. Old cycle spots congregate near the sun's equator. New cycle spots appear higher, around 25 or 30 degrees latitude.The region that appeared on Dec. 11th fitted both these criteria. It was high latitude (24 degrees N) and magnetically reversed. Just one problem: There wass no sunspot. That region was just a bright knot of magnetic fields. If, however, these fields coalesced into a dark sunspot, scientists were ready to announce that Solar Cycle 24 had officially begun, something they could not do, as no sunspot appeared there, but things changed radically early during 2008, when a real true active sunspot region was spotted by optical observations around the world. The new sunspot active region 981, at approximately 30 degrees latitude is a perfect match for all the criteria about the start up of a new solar cycle, so amigos, solar cycle 24 is now here with us. Now let me add that during the next several months sunspots from both cycles will be seen, those at high solar latitudes will be from cycle 24 and the ones near the solar equator will be the last ones from now coming to an end cycle 23…As more sunspots from cycle 24 appear, we may see an upward swing in the daily solar flux, and that should improve shortwave propagation all along 2008.Si amigos, yes my friends, oui mes amis… Cycle 24 is here and we are certainly happy that it finnally started !!! I’ll be back in just a few seconds after a short break for station ID. I am Arnie Coro in Havana……………….

You are listening to Radio Havana Cuba, the name of the show is Dxers Unlimited and here is item two of today’s program…Our antenna topics section will be devoted today to a special type of short wave antenna systems that are especially designed to provide short range ionospheric communications, using the so-called Near Vertical Incidence Skywave or NVIS propagation mode. NVIS antennas are very important for emergency communications systems, that use it when other systems suffer damages that reduce their traffic handling capacity or simply take them off the air. NVIS communications stations can be deployed anywhere and even one single individual is capable of setting up such a station in less than an hour, using low height wire antennas. Today, here at Dxers Unlimited’s antenna topics section we will be describing to you some of the most efficient NVIS antennas that have been used here in Cuba during tropical storms and hurricanes related emergencies, achieving a very high degree of reliability. The amateur bands used for NVIS systems here are 40 meters during the local daytime hours and 80 meters at night. The typical NVIS antenna is a half wave dipole installed at a very low height above the ground, so that the signal sent out by the antenna goes almost straight up at angles between 45 and 90 degrees. The signals come back to Earth with high intensity at distances from practically zero to around 700 kilometers around the transmitting station when the degree of ionization is at an adequate level. One interesting fact about NVIS communications is that they work quite well at rather low power levels, making possible for field stations to communicate using power outputs in the 10 to 100 Watt range. Base stations usually run higher power levels, but need to use the same type of low height antennas in order to assure that they are using the Near Vertical Incidence Skywave propagation mode. Another type of antenna recommended for these EMCOMMS or emergency communications stations is a full wave loop that is also installed at very low heights above the ground. One of the big mistakes that is often seen during communications emergencies is that field stations try to establish the NVIS mode links using vertical whip antennas, something that will prove to be a fruitless effort. Vertical antennas radiate at very low take off or departure angles, so very little radio frequency energy goes straight up as required for the NVIS mode to work. A few days ago a group of radio amateurs started to work on a new compact antenna system , that is smaller in size than a half wave dipole, while at the same time still been very efficient on the NVIS mode. The wire antenna , in its 40 meters band version requires just 11 meters of horizontal space between the masts or support structures, and is off center fed with coaxial cable and a coaxial cable choke to suppress the common mode radiation from the outside of the coax shield. The new antenna was designed using up to date sophisticated antenna modelling software and I am going to start testing the prototype next week. As soon as the preliminary test results are available, as always, I will be very happy to share them with Dxers Unlimited’s listeners and readers around the world.……

And now here LA NUMERO UNO, the number one most popular section of Dxers Unlimited, here at the first 2008 edition of the program, YOU have questions and Arnie tries to answer them…
Today’s question was sent by listener Mark in Ontario, Canada, and he wants to know more about low cost amateur radio equipment, because he tells me that he is on a shoestring budget, but nevertheless wants to start his own ham radio station. Well amigo Mark, not too long ago I made an attempt to create a low budget HF or short wave ham radio station, and after a few days , I was pretty happy with the results… Instead of trying to homebrew a sophisticated transceiver, my option uses a portable solid state short wave receiver that has a built in BFO or beat frequency oscillator. In my case the radio used for the project is a Sony ICF-7600-G portable, that is powered from four 1.5 volts penlight cells. The low cost ham station project includes a bandpass input filter and attenuator , with the transmit- receive switching incorporated into it, the 10 to 25 Watts power output solid state transmitter, and the AC power supply . No attempt was made to make anything miniature, in order to simplify the homebrewing. The Sony ICF7600-G is used with communications type earphones, and let me add that this is a CW , that is radiotelegraphy mode station, but a further development may turn it into a double side band voice station in the near future. The switching between receive and transmit is done while providing full protection to the front end of the portable receiver, and you can monitor the output of the transmitter by listening to the signal on the earphones. The whole station can be used for fully portable operation with a gell cell accumulator , that provides twelve volts DC to the transmitter, and 6 volts for the radio trough a simple one integrated circuit voltage regulator circuit. By using the SONY ICF-7600-G portable with its BFO, or any similar receiver, the low cost CW amateur station’s construction is simplified in a very significant way , because homebrewing a high quality digital readout receiver is quite a challenge, even for experienced radio amateurs. Assembling the bandpass input filter and RF attenuator and the transmit receive switching, the CW transmitter and the AC power supply while not a simple task is much more within the possibilities of homebrewers that are familiar with electronics and that can always obtain help from more experienced radio amateurs of your radio club. So amigo Mark, I have already e-mailed to you the block diagrams of this unique low cost amateur radio station project, as well as the circuit diagrams and some notes about the CW transmitter, the bandpass input filter and the transmit-receive switching system. This station is now on the air at CO2KK, operating on two bands, 40 and 20 meters with good results, despite the prevailing HF propagation conditions due to the extremely low solar activity. It like amigo Mark you are interested in learning more about this low cost approach ham radio station, just drop me an e-mail to arnie at, and I will send you the dot zip file with all the information required to duplicate this project.……

And now amigos, as always at the end of the show, here is Arnie Coro’s Dxers Unlimited HF propagation update and forecast … Solar flux is at a rather low 80 units, and the K index, the three hourly geomagnetic disturbance indicator was at a rather high figure of 5 early morning Saturday my local time here in Havana, at 12 hours UTC. This is due to the effects of a high speed solar wind that will disrupt HF propagation at high latitudes during the next two days. The winter Sporadic E season is now coming to an end, and we will have to wait until late April for the spring summer E skip season to start. The effective sunspot number is 20, and the daily sunspot number is now 20…

See you all at the midweek edition of the program amigos…
Send your signal reports,
QSL requests and radio hobby related questions to arnie at
Arnie Coro
Radio Havana Cuba, Havana, Cuba

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