Radio Havana Cuba Dxers Unlimited
Dxers Unlimited's week end edition for 4-5 August 2007 By Arnie Coro radio amateur CO2KK Hi amigos radioaficionados worldwide... this is the weekend edition of your favorite radio hobby program coming to you from sunny Havana, where local temperatures have gone up to more than 35 degrees Celsius, and frequent summer thunderstorms have limited my radio monitoring time, because amigos, when the storm clouds approach, your only option is to disconnect all radio equipment from the antennas, the power line and it is also advisable to disconnect the earth grounding system too. ITEM TWO: Extremely low solar activity continues.... the July official sunspot average published by the Royal Observatory of Belgium was 10, a clear evidence that we are still going trough the solar cycle's minimum...And the most recent forecasts are telling us that during the next several days a blank solar disk is to be expected, with zero sunspots prevailing together with rock bottom figures of the 10.7 centimeters microwave solar flux. The extremely low solar activity is causing very poor daytime propagation on the frequencies above 15 megaHertz... More about solar activity and the HF plus low band VHF propagation update and forecast as always at the end of the program... ITEM THREE: Coming up in a few seconds, after a short break for station ID... I am Arnie Coro, radio amateur CO2KK your host here in Havana... ............... Yes, you are listening to the weekend edition of Radio Havana Cuba's Dxers Unlimited, and here is ITEM THREE... Our technical topics section of the show, that is devoted today to answering a question from a listener. He is experimenting with the Closed Coupled Resonators type of multiband antennas and wanted to know more about this system that uses a single feedline connected to one of the three close to each other antennas... Up to five antennas can be fed using this system, but the more common CCRs or closed coupled resonators antennas are two band or three band systems. As a matter of fact there is a very well designed commercial amateur three band Yagi antenna array that very succesfully uses the CCR system for the antenna's active elements. Here is now my answer to the request by the Dxers Unlimited's listener request: Dear amigo: Nice to hear from you again, and learn about your antenna experiments. Here is all that I can tell you about my experience with the CCR Close Coupled Radiators antenna system The CCR wire antennas for the HF bands that I have tested here seem to work very well after spending time adjusting them. The maximum number of wire antennas that I think is possible is 3 or perhaps 4. You can start with a half wave dipole , fed via a 1 to 1 balun and using a 50 ohms qood quality, well shielded coaxial cable. Tune this antenna , for example, to resonance at 10.1 megaHertz ( the 30 meters band ). Then you can add a wire cut as a half wavelength antenna for the 14.1 megaHertz frequency, placing it about 10 centimeters ( 4 inches away ) from the "fed dipole " Your third antenna of the CCR system may be a half wavelength antenna for the 18.1 mHz band, placing it also at the same distance of the "fed dipole " ( This third one could also be for 21.1 , 24.9 or 28.4 mHz, as required ) Then you must work with your SWR meter to obtain the best possible SWR on the three antennas, something that is achieved by NOT MODIFYING the length of the "fed dipole", but doing so with starting with the 20 meters band ( 14.1 mHz antenna ) and then optimizing the SWR for the 18.1 mHz antenna. You may notice some interaction between the adjustments, but with the 10 cm ( 4 inches ) separation, this won't be really significant and you will end up with a nice three band system that works very well You may attempt to add a 4th wire , cut as a half wavelength element for the 15, 12 or 10 meter bands, and with very careful adjustments the 4 bands CCR antenna will also work quite well, but the three band system is easier to adjust. You may install two antennas, one for the 40,30,and 20 meters band and another one for 20,15 and 10 meters band. Vertically polarized CCR antennas are trickier to adjust because of the instability caused by the ground-counterpoise system that you may have in use... In general CCR verticals must be installed with no less than 8 radials cut for each of the bands that you are going to use, or at least 8 radials for the lowest frequency band.. The radials must be 1/4 wavelength long, and you can intertwine another set of 8 radials 1/8 wavelength long at the lowest operating frequency. I hope this helps you, and as a good friend said when he saw the CCR wire 3 bander , the question is why don't simply tie the three dipoles together at the center and feed the three at the same time via a one to one balun... ANSWER: Because the CCR is a new concept, and as I told him, one always wants to learn about new antennas. Besides that, it seems like the CCR three bander produces a cleaner vertical pattern than three pararell fed dipoles ... And the next day, I received a very nice answer telling me that his three band antenna was working very well on the 40, 30 and 20 meters band. He used fiberglass insulators to keep the three wires separated from each other by about 10 centimeters or 4 inches, the distance that was found to provide the best coupling and lowest standing wave ratio. ................. You are listening to the weekend edition of Dxers Unlimited, coming to you when the daily solar flux is at the rock bottom levels of between 68 and 72 units... Now here is item four : Amateur radio satellites are in orbit, not one or two, but several of them, but they all seem to be getting very little use ... Today I will try here to attempt to understand why the existing amateur radio satellites are seeing such little use, and the first thing that comes to my attention is that among radio amateurs there is very little knowledge about ham satellites and how you can operate using them. After the fiasco caused by the failure of the Oscar 40 super amateur satellite that was supposed to last for many years in its elliptical orbit, interest in amateur satellites dropped dramatically,and in my opinion it has never recovered. Another contributing factor to the present low use of ham satellites was also the failure of the popular Russian RS10 and RS12 easy sats, that could be accessed using very simple antennas and equipment. Now there are some signs of a revival in interest in the use of amateur satellites, that focuses mainly on using them during ham radio contests to boost the number of points by both club and individual stations, at a moment when as we all know well, HF propagation conditions are very poor. But, again, after carefully attempting to find out why ham radio satellites see such little use nowadays, there seems to be yet another important element, and that is the fact that the presently available satellites are at very low altitude Earth orbits, so the time available to make two way contacts is really very limited for even the best possible conditions between two stations... Prospects for a satellite with similar operating characteristics as the doomed Oscar 40 are not optimistic at all, so my point of view is that amateur radio satellite communications will remain at the present low ebb for years to come... Yes, it is one of the more than 81 ways you and I can enjoy the radio hobby, and at the present time it doesn't require a lot of expensive equipment or sophisticated antennas...So, if you are already an amateur radio station operator, explore the possibilities of testing your ham station's satellite communications possibilities...At these times of extremely poor HF propagation conditions , satellites keep operating as usual, because they don't depend on solar activity to provide two way communications... ....... This is Radio Havana Cuba, the name of the show is Dxers Unlimited and here is our next item... the ever popular, la numero uno YOU HAVE QUESTIONS AND ARNIE HAS THE ANSWERS... Today's question was sent by listener Doris from Atlanta, Georgia. She ASKS ARNIE , why is it possible for her to sometimes pick up distant FM stations from her tenth floor apartment location, that she can't hear on her car radio... Well amiga Doris, the difference has to do with what engineers know as effective antenna height, an ever important parameter for VHF, UHF and Microwave operations... Your tenth floor apartment's effective height above average ground extends the coverage of your FM radio a lot as compared to the range that you can achieve with the car's FM radio antenna that is at no more than about 2 meters or six feet above the ground... By the way amiga Doris, I am sending to you via e-mail the complete detailed building instructions for a nice FM broadcast band antenna that can be built using wire and PVC tubing. It is a two element cubical quad that I have used here successfully to pick up FM broadcast band DX from distances of up to two thousand miles when sporadic E openings have happened... And now amigos, as always at the end of the program , here is Arnie Coro's Dxers Unlimited's HF plus low band VHF propagation update and forecast... Solar activity is , and will continue to be for the next several days at extremely low levels... with solar flux between 67 and 72 units and daily sunspot count at zero or very near zero... Expect possible sporadic E openings by the end of the week, according to the most recent forecasts... Expect daytime maximum useable frequencies not higher than 18 megaHertz, and the best propagation conditions to be available always after your local sunset. Join me next Tuesday and Wednesday for the mid week edition of Dxers Unlimited amigos, and don't forget to send me your signal reports and comments about the program to [EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]> , or VIA AIR MAIL 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 [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
