Radio Havana Cuba Dxers Unlimited Dxers Unlimited’s weekend edition 1-2 September 2007 By Arnie Coro Radio amateur CO2KK
Hi amigos radioaficionados… I am Arnie Coro , radio amateur CO2KK in Havana, inviting you to stay here on this frequency or world wide web connection listening to Dxers Unlimited’s weekend edition… Well, here we are, now right at the start of the autumn equinoctial DX propagation season, as I like to properly call it… Because there is no doubt that no matter how the solar cycle is behaving as the autumn equinox approaches short wave propagation conditions around the world improve dramatically for a period that usually lasts from four to six weeks… starting just now, when during the first week of September one starts to notice how the HF bands begin to improve… For example 20 meters, the queen of radio amateur DX bands will be open to one part of the world or another for many more hours every day… Wednesday afternoon I heard a very loud signal on 20 meters single side band coming from the United Kingdom into the Caribbean… The UK station was benefitting from the typical local sunset propagation enhancement, and he was an S 9 plus 10 dB on peaks perfect copy on my 20 meters band half wave dipole “slopper” antenna, that is tilted at a 45 degrees angle with the lower end aiming at Europe, to make one of the lowest cost “beam antennas” that you can imagine… So amigos, follow your friend’s Arnie Coro advice and devote more time, from now on to operating your radios, because propagation conditions will continue to get better and better for the next three to five weeks… Stay tuned because after a short break for station ID, Dxers Unlimited’s weekend edition will continue in afew seconds… I am Arnie Coro in Havana… ……. The name of the station is Radio Havana Cuba, we have been on the air since 1961, and we are proud of providing our listeners with one of the world’s best QSL services… Yes , we do verify reception reports with a nice , beautiful QSL CARD… a collectors item by all standards amigos… Send your signal reports, comments about our programs and radio hobby related questions to [EMAIL PROTECTED] or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba… And now here is item two, also HF propagation related… Tropical Bands propagation also benefits from the autumn equinox season, and this is your opportunity of logging some nice catches on the 60 meters Tropical Broadcast Band, the one that still has a relatively large number of stations on the air… Let’s start with our own Radio Rebelde, from Havana operating 24 hours a day on 5025 kiloHertz for our domestic near vertical incidence skywave coverage of the Cuban archipelago, something that the Tropical band is able to do with just one transmitter and a special NVIS antenna system… But, the NVIS antennas also have minor lower take off angle lobes that send the signals at much longer distances, and that’s why you can pick up Tropical Band domestic services from across the globe… Here are a few stations from Africa that may be logged in North America and Europe during the present autumn equinoctal DX season… Starting with ANGOLA.on 4950 , from Mulenvos, but beware that this transmitter is usually with very low modulation index.. From the Republic of Benin, on almost exactly the same frequency as Radio Rebelde on 5025 kiloHerts is Radio Parakou, that you may catch when late in the evening daylight saving time, around 0500 UTC Radio Rebelde’s 50 kiloWatt transmitter on 5025 kiloHertz is off the air for routine maintenance…something that happens about once a month… at other times picking up Benin of 5025 kiloHertz is a matter of luck, when propagation changes in favor of the African station over the Cuban on the same channel. Moving just 5 kiloHertz up the 60 meters Tropical Band from 5025 to 5030 kiloHertz you may sometimes pick up BURKINA FASO,’s Radio Burkina from the capital of that African nation Ougadougou, again when a the station from Costa Rica on the same frequency is not on the air, or propagation at your location favors the African continent.. These are just four examples of Tropical Band stations that you add to your logbook during the present equinoctial DX season amigos, but there are many, many others that make very interesting listening ,especially for the nice music they play that you will very rarely if ever hear at your local FM one hundred thousand watts stereo powerhouse !!! …. Now amigos, here is our technical topics section, that will be devoted today about the growing interest among radio amateurs to use AM modulation, and by that I mean standard double side band plus full carrier AM, the first way of superimposing voice and music on a radio carrier wave… A few days ago during a 40 meters bandscan that I was doing late at night with my REGENERODYNE homebrew receiver set for picking up CW and Single Side Band station, a loud signal produced a really loud heterodyne… backing off the regeneration control, the AM signal came in with excellent audio quality. It was a radio amateur from Ohio, USA, operating a vintage transmitter that he described as more than 50 years old. The four dash four hundred tetrode final , modulated by a pair of eight thirteen tetrodes was certainly providing excellent reception. The proud owner of the AM rig was using a simple half wave dipole , so his actual antenna gain was zero db or decibels over a dipole. He told the stations he was talking to that he was using a 1950’s vintage Viking One transmitter at a very low power setting to drive the big tetrode that was fed with three thousand volts on the anode… The classic class B modulator with the eight thirteen tetrodes provided all the audio needed for one hundred percent modulation and more, something that as he properly explained is very important if you want your AM signal to provide the highest possible quality sound with very low distortion… But this Ohio ham operator was not the only one I have heard recently, because as I just said more and more radio amateurs are coming back to AM to enjoy the beautiful audio quality that is possible using that form of modulation, while at the same time keeping on the air some nice antique equipment…. I have heard recently AM amateur stations also on 20, 15 and 10 meters, and the hams operating those stations seem to enjoy it a lot, as they are not chasing DX or working one station after the other in contest… they are just relaxing , talking to each other and discussing some very interesting technical topics, like the design and construction of amateur radio transmitters that use amplitude modulation techniques, not only the classical ones everybody knows about, but some of the more advanced pulse width modulation technology that has become almost a defacto standard for AM broadcast stations but that has seen so far very little if any use among the world’s radio amateurs. …… You are listening to the weekend edition of Dxers Unlimited coming to you from Havana, and here is now LA NUMERO UNO, the number one most popular section of the show… YOU have questions and your amigo Arnie tries to answer them… Here is today’s question sent by listener Gabriel from Atlanta, Georgia , USA… Gabe, as he signs his e-mail, wants to know more about regenerative receivers and why they seem to have such a devoted group of people around the world always experimenting with those circuits that , he very well describes them, do require a lot of attention to construction details in order to achieve good performance… Well amigo Gabe, it may be a matter of accepting a challenge, or the pride to be listening to a relatively simple radio that you have built yourself, and that picks up distant stations better than your store bought radio… Maybe those are the main reasons that make radio hobby enthusiasts enjoy so much discussing the circuits with friends at the e-mail lists devoted to regenerative receivers, changing parts values to see how the performance of the radios change, or experiment with rarely known circuits used in the very early days of radio and long forgotten, like the so called “space charge tetrodes ”, that became popular because it made possible to build a radio receiver that used only one single 6 , 9 or 12 volts battery…. And this of course was happening when radios were battery operated and required expensive so called B PLUS B+ batteries for providing the high voltage to the vacuum tubes anodes… Just for your information amigo Gabe, I have sent to you already , via e-mail the circuit diagram and my notes of a regenerative receiver that uses low voltage for feeding the anodes or plates of the vacuum tubes, in other words, it doesn’t require the use of a high voltage power suppy, because both the tubes filaments and anodes are fed from the same 12 volts DC power supply… Maybe you can homebrew this receiver diagram that has given many radio enthusiasts many hours of nice AM broadcast band and shortwave listening… Please note amigo Gabe that the vacuum tubes types used are not critical at all, so you won’t need to spend a lot of money buying specific tube types that are much sought by HI FI audio hobbysts who are erroneously led to believe that certain tube types have some magical qualities that make their audio sound better than others… My prototype of this cascode regenerative 12 volts operated set was built and is still operating using vacuum tubes recycled from TV sets that were retired from service… I never even tested those tubes , just plugged them in, and the radio started to provide excellent reception , so I just left them there amigo !!! Now for those of you wanting to learn more about regenerative receiver circuits, both vacuum tubes and solid state, just send me an e-mail to [EMAIL PROTECTED], and I will send you a few circuit diagrams plus the address of one of the most popular regenerative receivers discussion forums on the Internet, that I strongly recommend you to join, as it is a treasure chest of knowledge that its members share with each other in a most civilized and educated way, with a spirit to share what each one knows that is an excellent example of how the Internet can be used for the promotion and development of the radio hobby … And now as always at the end of the show, here is Arnie Coro’s Dxers Unlimited, HF plus low band VHF propagation update and forecast.. Solar flux still at very low levels and a new sunspot group is growing, but it would not produce big solar flares according to what can be seen. The equinoctial propagation conditions are now very much in progress , so if the flux increases above 80 units we are going to see much better propagation by mid September… See you all at the mid week edition of Dxers Unlimited, next Tuesday and Wednesday UTC days amigos !!! ---[Start Commercial]--------------------- Preorder your WRTH 2007: http://www.hard-core-dx.com/redirect2.php?id=wrth2007 ---[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
