RADIO HABANA CUBA
DXERS UNLIMITED
MID-WEEK EDITION
TUESDAY, APRIL 10, 2001
By Arnie Coro CO2KKSend your comments, questions and ideas to: arnie@radiohc.org
Hi amigos, welcome to the mid-week edition of your favorite radio hobby show on short wave and on the web, and now also available via our fast majordomo list server when you subscribe to Dxers Unlimited's mailing list. I am Arnie Coro, radio amateur CO2KK, your friend here in Havana, and here are the headlines:
Solar activity HIGH, fireworks continue, and we may see more X class flares during the next few hours... Latest X class flare was an X2 at 0525 UTC Tuesday, April 10th and two hours later a C8 flare followed. According to my optical solar observations, sunspot region 9415 has the potential for more flare activity, and it is now very near the center of the solar disk, in what scientists describe as a geoeffective position -- that, translated into common words, means that if there are more new coronal mass ejections from region 9415, it is very likely that the Earth will receive the full blast of the stream of high-velocity solar particles.... By the way, Wednesday and Thursday may see nice aurora borealis at latitudes above 40 degrees North, when particles from a previous coronal mass ejection interact with the Earth's magnetosphere.... Again, another translation into everyday language, be prepared for yet another possible geomagnetic storm that may reach major or even severe levels.
Headline number two: Spring tropospheric VHF, UHF and Microwave DX season now in full swing... radio hobbyists in North America, the Caribbean and Southern Europe are already having a lot of fun picking up DX via tropospheric ducting... Here in Cuba, two meter ham band operators have caught at least three major openings during the past several days, and worked some very interesting stations using the FM mode, as single side band VHF and UHF radio equipment is almost nonexistent here...So, hams do what they know how to do to best: use whatever equipment they have to work DX... and although the FM mode is a wideband communications system, high gain antennas and low noise pre-amplifiers push 2 meter FM band DX to amazing distances, even though the mode is at a great disadvantage when compared to the much narrower band SSB and CW....
Headline number three: Yet another simple radio receiver..... it is a vintage set, one single vacuum tube, but it's both easy to build, and works very well; it even has bandspread coils for the hambands... it came to my attention via long-time Dxers Unlimited's listener Tim in the USA.... So, I have added it to the list of simple radios circuit diagrams that you can request by sending an e-mail to arnie@radiohc.org, amigos! Stay right on this same frequency, sharpen up the tuning, peak the antenna trimmer if your radio has one; I will be back with you in a few seconds. My sound engineer and producer is Margarita Delgado, I am Arnie Coro in Havana, always QRV on 28 dot five hundred, 10 meter band whenever it's open...
You are listening to the mid-week edition of Dxers Unlimited, solar activity is high, the effective sunspot number, the one you will want to feed to your propagation forecasting software, is a nice and cool 121... and we may see it staying there or even moving up a bit during the next few days. By the way, a new freeware propagation forecasting program appeared a few days ago... It is available for downloading at a website, and I am now in the process of evaluating it.... so far, I am very pleased with the results...
Have paper and pencil or pen ready, because in a few minutes I will give you the URL of the website where you can download this new amateur radio contribution to the hobby... Once again, we see here a case of a highly sophisticated and very well-written program made available to the worldwide radio hobby community by someone who donates all his talent, effort and time devoted to develop and debug such a complex piece of software... There are many similar examples, like the recently available MMTTY sound card operated radio teletype program, and the ARGO ultra weak signal slow CW morse code detection software.... Refreshing to see what nice people are doing in the interest of our nice hobby... Don't you agree? By the way, I am preparing a list of between 10 and 15 computer software programs that can be downloaded via the INTERNET as freeware, and will probably add it at the end of one of Dxers Unlimited's scripts that are know available via our e-mail distribution list.... if you want to receive Dxers Unlimited's scripts absolutely free of charge and automatically, as soon as they are posted at our website, here is how to do it.... it is very easy indeed.... send an e-mail message to majordomo@rhc.cu, and then in the subject line or in the body of the message type subscribe dxers_l, and wait for the majordomo list server handling system reply, telling you that you are subscribed and providing instructions on how to unsubscribe when you wish to do so.... Then, you will be receiving Dxers Unlimited's scripts twice-weekly, with occasional interim propagation alerts or other radio hobby-related information. Messages will always be very short, barebones technique, as there are many radio hobbyists in underdeveloped areas of the world that have to pay for their e-mail service with a time of connection to the server tariff or even by the number of kilobytes received.... So amigos, my friends, mes amis... meus amigos...yes in four languages, Spanish, English, French and Portuguese, as there are Dxers Unlimited's listeners around the world that speak those languages at home, although, of course, they pick up the show in English!!!!
And now, the ever-popular ANTENNA TOPICS section of Dxers Unlimited... today I will tell you, once again, about L.B. Cebik's 13.4 meters long wonder antenna.... to which yours truly added a very easy modification that further improves the performance of this system, designed to operate from 7 to 30 megaHertz, but that has also shown that it works on the 6 meter band, too. For those of you not familiar with Dr. Cebik's 44 feet, or 13.4 meters long antenna, it was designed using today's most advanced antenna computer simulation software, and when used with an open wire transmission line, or a balanced shielded dual coax feeder, the antenna provides a very efficient radiating system which takes up very little space... The 13.4 meters wonder antenna must be installed horizontally, and the feedline must be connected to your radio via an antenna tuner...
NOW, here is my contribution to the development of this excellent system: Instead of using one single wire on each leg of the antenna, I used first three and then five wires, all of the same length, that is 6.7 meters or 22 feet... Results obtained when adding the two additional wires to each leg of the antenna to effectively transform the system into a fan dipole, showed that the bandwidth increased significantly, something to be expected as the Q, or sharpness of tuning, of the antenna went down. The added wires are installed so that they fan out from the center insulator, in such a way that they end at 2.25 meters above and below the center wire.... For those of you who still think NON METRIC, that is roughly seven feet above and below the center wire...
The 13.4 meter long dipole, with the additional two wires on each leg to form a fan dipole, has proven to be an excellent general-purpose short wave receiving antenna, that is better than the classical TTFD, or tilted terminated folded dipole for transmitting, but that does require an antenna tuner for both receiving and transmitting, something a well-designed TTFD does not need. In other words, if you have space for only one HF antenna at your location, the choice between a 13.4 meters FAN DIPOLE and a TTFD will depend on just one bit of information... If you are going to use the antenna as a receive-only system, then by all means install a modern version of the TTFD, but if you ever plan on using your antenna for transmitting, the 13.4 meters fan dipole with a set of baluns and the PI network antenna tuner, will be the right choice.
Baluns are essential with the balanced dipole, because your feedline is balanced, and your PI network tuner is an unbalanced device... At CO2KK, my ham radio station, I use two baluns that can be switched... a one-to-one, and a four-to-one.... By experimenting with both at different frequencies, I have found which of them is the right one to use for each amateur band.... Yes, amigos, building your own antenna system is a lot of fun, you will save money, and enjoy using something that came out of your own hands... and for those of you at higher latitudes, a question: isn't antenna installation weather just around the corner??? Sure, so start gathering the necessary materials for either a TTFD or a 13.4 meters long CO2KK FAN DIPOLE... and if you feel like you are in need of more information about these two excellent short wave antennas, just drop me an e-mail or send an Air Mail postcard, and I will be more than happy to answer your questions and clear your doubts amigos!!!
The CO2KK FAN DIPOLE, an upgrade of L.B. Cebik's excellent design of a 13.4 meter long dipole fed with open wire or shielded balanced line, is an nice overall performer from 5 to 50 megaHertz for reception, and from 7 to 50 megaHertz for transmitting using, as clearly stated here, a wide band PI network antenna coupler and a balun, or balanced to unbalanced transformer. The 14 meter long TTFD or Tilted Terminated Folded Dipole, using an 800 to 900 ohm non-inductive resistor termination and a 12 to 1 or 16 to 1 balun, is also a nice antenna for receiving, but when used for transmitting it will show negative gain; in other words, it will not radiate as efficiently as the FAN DIPOLE especially in the range from 7 to 10 megaHertz....
And now amigos, as always, at the end of the show, here is Arnie Coro's Dxers Unlimited's HF plus 6 meters propagation update and forecast.... Extremely interesting propagation conditions will prevail during the next three to five days.... these conditions are closely linked with the behavior and effects of solar activity related mostly to solar active region 9415, which is now almost right at the center of the solar disk, in what scientists describe as a geoeffective position. Be ready for yet another geomagnetic disturbance to start sometime Wednesday, and we may see others following during the next few days....
For 6 meter band operators, be on the alert for abnormal propagation associated with F2 layer enhancements due to the geomagnetic disturbances.... and we may also see F2 to sporadic E coupling, extending the range of 50 megaHertz DX well above the classical Trans Equatorial Propagation active region above and below the Equator...
For AM medium wave band DXers, a special alert, as some real nice DX may fill in the empty channels left by the stations that are going into the high absorption areas during the geomagnetic storms.
Yes, short wave propagation is now really very interesting, so I will be spending more time on the radio and less time at the electronics workbench.... follow my advice and do the same!
ENJOY.... See you on 28.5, 21.3 or 14.2 megaHertz when the bands are open for a nice two way QSO, if you are already a ham radio operator, and if you are not... here is Arnie's question... what are you waiting to pass your amateur radio license test? Don't forget: E-mail your comments and questions, signal reports and QSL requests to me!
Arnie Coro CO2KK
Havana, Cuba
10 April, 2001Postal address:
Arnie Coro, "Dxers Unlimited"
Radio Havana Cuba, Havana, CUBA
e-mail: arnie@radiohc.org
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