Radio Havana Cuba Dxers Unlimited Dxers Unlimited’s weekend edition for 17-18 February 2007 By Arnie Coro Radio amateur CO2KK
Hi amigos radioaficioanados around the world and in space, welcome to the weekend edition of your favorite radio hobby program , I am Arnie Coro in Havana, and here is item one… its related to the ongoing solar cycle’s minimum… When HF propagation conditions are poor, then it’s time to enjoy many other aspects of the radio hobby, like homebrewing receivers , installing new VHF and UHF antennas, and even attempting to do some interesting radio astronomy experiments like listening to planet Jupiter’s rather easy to pick up signals on frequencies within reach of many short wave receivers and using very simple , easy to install antennas . If you happen to have an amateur’s band Yagi antenna capable of operating on the 15 meters or 21 megahertz ham band, then you will certainly be able to pick up Jupiter’s natural radio signals regularly… By the way, they sound like waves slowly moving over a sandy beach, and going back again… Stay tuned for more radio hobby related information and know how coming to you from Havana. I’ll be back in just a few seconds amigos !!! ….. Si amigos, sure, after many years of enjoying the radio hobby, I am still fascinated when setting the alarm clock for two o’clock or three o’clock in the morning and getting ready for yet another medium wave AM broadcast band Dxing session… Last evening was no exception, except that I didn’t need an alarm clock, because my little two years old baby Claudia likes to wake up around that time asking for her milk bottle… Roxana my wife woke up first and was already changing the baby’s diaper when my new super-regenerodyne receiver was already picking up its first DX station, one that I use as a propagation beacon, because I know the power its delivering to the antenna and its location East of my QTH gives a very good idea about ionospheric absorption especially as sunrise approaches. It is Radio Rebelde’s 600 kiloHertz relay in San German, Holguin province of eastern Cuba… The signal coming in from this station was excellent, so I moved up to the top end of the AM broadcast band, but checking the local time, and making the conversion to UTC, I sadly realized it was already too late to try to pick up European stations… Maybe tomorrow, as almost ideal AM broadcast band propagation conditions will almost surely continue, little baby Claudia will wake up a little earlier, and I will be able to pick up at least one or two Europeans, that by the way, for your information, in case you are not familiar with that fact, operate on a 9 kiloHertz channel spacing, so their presence is many times learned by the whistling heterodynes caused by their carriers beating with stations in the Americas that operate on a 10 kiloHertz channel spacing. The new super-regenerodyne, especially built for the low ebb of the solar cycle, runs the regenerative detector in the frequency range from 100 to 500 kiloHertz, so tuning up the whole AM broadcast band required splitting it into3 segments, starting on 520 kiloHertz and ending slightly above 1700 kiloHertz. Lacking the quartz crystals for the frequency conversion, I used a highly stable Franklyn type oscillator for the first conversion with excellent results. To receive the segment from 520 to 920 kiloHertz, the Franklyn oscillator works at a fixed frequency of 620 kiloHertz, something that is not a very nice solution because it completely blocks reception on several channels… The segment from 920 to 1320 kiloHertz, requires the local oscillator of the first conversion to operate on 1020 kiloHertz, and here again several channels are blocked. The third and last segment of the AM band , from 1320 to 1700 kiloHertz requires the local oscillator to operate on 1420 kiloHertz, so I have the same problem with several channels lost to the presence of the local oscillator signal within the passband of frequencies that I want to listen to… But, let me say that despite this design flaw, of which I was fully aware, the sensitivity and selectivity of this AM broadcast band receiver is simply amazing. The operation of a regenerative detector at frequencies as low as 20 kiloHertz makes the control of regeneration as smooth as one can imagine, so you can operate the detector at its highest selectivity setting allowing for single side band reception, something quite useful when hunting for transatlantic AM band DX stations. Now that I have obtained such an interesting experience with this radio, a new one will be built, in which the AM broadcast band will be up converted to the frequency range from 28 to 29.2 megaHertz…, using a specially designed quartz crystal controlled converter and a double balanced mixer… The “tail end” of this up converter is going to be my single band 10 meters transceiver, that due to the diminishing solar activity will see little use to communicate during the next several years, but could play a useful role as yet another AM DX receiver tail end… By the way, the upconversion needed a single quartz crystal for the local oscillator, that fortunately happened to be in my junk box !!! ……. Yesterday I made contact with two long time ham radio friends, one was vacationing in the Caribbean and talking to me on 17 meters from the balcony of his hotel room, using a helically wound antenna just 2 meters high… and the other was enjoying a stay with one of his daughters that lives in a farm and was using a real long wire antenna, no less than 400 feet long… We had very nice QSO’s, and for those of you that are not familiar with that term, its an abbreviation for a two way contact used by the early days radio operators… I’ll have a bit more time to be on the air during the next 10 days or so, and expect to have many more opportunities of meeting with ham radio operators around the world …The best bands for making contacts during the winter season are, 17 and 20 meters during local daytime hours, and 40 and 80 meters during your local evenings, but we may see brief openings on 15 meters too. ….. Now here is the very popular technical topics section of the program… Operating your radios from rechargeable batteries requires taking care of them, so that they will really last the number of expected cycles. It is amazing to see how expensive rechargeable batteries are sometimes turned into worthless units because their owners didn’t take proper care of them… Gaining knowledge about the characteristics of nickel cadmium, nickel metal hydride or lithium ion rechargeable batteries is very useful , because if you apply the know-how, your batteries will live a lot longer. My advice is that you simply forget about nickel cadmium batteries, and buy, from now on, nickel metal-hydride units,as they can provide more operating time on the same size of battery, and also don’t have the so called memory effect of the nickel cadmium old technology batteries. Recent advances in the design of chargers for the nickel metal hydride cells make possible a much longer useful life of those units. And don’t forget that the lithium-ion batteries do require a special charger and can not be charged with any other type of charger, as they may be destroyed or even explode if improperly charged… Also, let me add that I prefer to run my receivers, whenever possible, using batteries, as by using them, noise coming in from the power line is simply reduced to zero !!! ……. Receiving here lots of nice e-mail messages, post cards and letters here, and also a few FAX letters too. Keep them coming amigos, is always nice to read your comments about the program that are full of new ideas to make Dxers Unlimited a bit better on every new edition. Item three: The ultra compact dipole antenna that I talked about here recently edition here on Dxers Unlimited continues to bring in lots of questions among listeners around the world. The most frequently asked question about this topic, was if this could be designed as a broadband antenna, and the answer amigos is NO, the ultra compact dipoles designs are narrow band antennas, that most be built for operating on a single amateur radio band if you want to transmit with them, but that may be used for short wave listening over a much wider range of frequencie.Amigos Lester, Charlie and Albert, frequent Dxers Unlimited listeners asked thee possibility of using the compact dipole in a vertical configuration to obtain a lower radiation angle ... Si amigos, yes, you are right, the compact inductively and capacitively loaded dipole is ideal for installing it in a totally vertical or sloping configuration. As a matter of fact, I have just recently seen a commercial antenna design that follows that idea pretty closely...But personally I prefer to use this antenna as a very efficient sloper, because it provides a small but significant gain in the direction towards which the wire is sloping. The ideal sloping angle is between 30 and 45 degrees, in order to form the best possible directional pattern with the ground reflection... …… A quick reply to a question sent to our ASK ARNIE section of the show… Yes amigo Craig from Toronto, Canada, you are absolutely right in your analysis… not all compact fluorescent energy saving light bulbs are created equal, in other words you may install new ones that are extremely quiet , that is they almost don’t generate radio frequency interference at all,while others similarly rated may wipe our short wave reception far away from where the energy saving light bulb is installed… And don’t be surprised with some commercial brands of energy saver fluorescent causing problems with your TV set and VCR remote controls too… In more than one occasion I have seen remote control systems that work using infra red signals go crazy when an energy saver light bulb was installed near the TV and VCR … Things returned back to normal by just turning the light OFF !!! Of course that the only cure for the problem is replacing the energy saver with a better quality one, or even better yet, try one of the new Ultra Bright Light Emitting diode lamps, but check that they don’t use a switched mode power supply inside the bulb, before buying it… ---[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
