Radio Havana Cuba Dxers Unlimited's weekend edition for Sunday Sunday 9 August 2015 By Arnie Coro radio amateur CO2KK

Transcription

1 Radio Havana Cuba Dxers Unlimited's weekend edition for Sunday Sunday 9 August 2015 By Arnie Coro radio amateur CO2KK Hi amigos radioaficionados around the world... I am your host here at Dxers Unlimited, our station's twice weekly radio hobby program, my name is Arnaldo Coro, but on the ham radio bands everyone knows me as Arnie... which by the way is a lot easier to pick up on the air than Arnaldo... Here is now item one of today's program... I have yet to confirm it, but it looks like crew members at the International Space Station, the ISS, continue to use on the air their own amateur radio call signs... The astronauts that left Planet Earth to dock their spacecraft with the ISS for a more or less long stay in space in many cases have obtained their respective countries' amateur radio licenses so they are ham radio operators in space... The activity of the stations aboard the biggest ever manmade object in space attract the attention of many newcomers to our hobby... Item two: also space related. optical observations by the astronauts aboard the ISS have confirmed the existence of a form of upward moving lightning bolts known as sprites... they originate at the top of the cumulus nimbus clouds and go up into the ionosphere.

2 According to recent research results the sprites hitting the bottom of the ionosphere are now considered to be yet another source of ionization that reaches the E layer of the ionosphere, effectively creating Sporadic E clouds. Scientists continue to be puzzled by the existence of Sporadic E highly ionized clouds that form and disappear mysteriously. By the way, the Sporadic E clouds that are much more frequent during the summer months sometimes are able to send back to Earth frequencies as high as 220 megahertz, and there is at least one instance of a Sporadic E event so intense that signals on the 70 centimeters (or 420 to 450 megahertz) amateur band were bent down to Earth instead of keeping their trajectory into space. Item three: Home brewing of radio gear is a lot of fun, especially if you are helped by more experienced hobbyists that prevent possible failures that are typical of beginners. The active role of amateurs that have had experience building their home equipment is put to very good use by radio clubs during the so called buildathlons... a meeting where a kit of parts to build a project is made available, so that each participant can assemble it under the supervision of the more experienced radio amateurs at the event. This is a way to assure that participants will go home with a fully functioning unit, something that has a very positive effect in further promoting the interest in home building of radio gear. No frustrations from non working projects after

3 they are powered up the friendly experienced amateurs are at hand to help find and remove the bugs... But more sophisticated projects that cannot be assembled in a few hours, do require a different approach in order to avoid costly and disappointing failures... Today I will tell you how we are making possible that a number of Cuban radio amateurs will be able to assemble a fully functioning ham radio short wave transceiver... More about this topic in a few seconds when Dxers Unlimited's weekend edition continues after a short break for station ID. I am Arnie Coro, radio amateur CO2KK in Havana.... Si amigos, sure, this is Radio Havana Cuba, the name of the show is Dxers Unlimited and here is more information about the project that is an environmentally friendly effort that is saving from the dumpsters a lot of valuable electronic components. It all started during the summer season. Several radio club members that hold a third class license made the proposal of starting a project that could put them on the air on the 40 meters band, now that recent rules and regulations changes opened up for them the segment between 7100 and 7125 kilohertz.

4 As a matter of fact this new ruling also opened up to third class license operators the 80 meters band segment between 3550 and 3750 kilohertz. What they wanted was a simple transceiver for the 40 meters band, because they have heard many times that propagation conditions on 80 meters here in Cuba are not very good during the daylight hours, while 40 meters provide nationwide coverage while running low power and simple antennas. Phase one of the Super Islander Mark Six double sideband and CW transceiver was the way to go... Phase one means laying out the complete detailed technical specifications for the rig, and drawing the circuit diagrams... Phase two comprises the gathering of all the required parts, something that has benefited from the availability of such items as broken down computer power supplies, UPS units that are no longer possible to repair, as well as computer monitors, TV sets and other that may be considered as just electronic junk. But, inside those units we have found and recovered a large number of electronic components that after being tested are now in storage pending the assembly of module number one of the Super Islander Mark Six. The design of this simple, no frills, transceiver began by calculating the power supply unit required. We have started to assemble the prototype power supply module, using the chassis and cabinet of a nice looking computer UPS, that will also serve to house the loudspeaker of the transceiver.

5 No attempts are made to produce a miniature size rig, as we want it to be an easy to maintain radio. With a lot of space between its components. We found that a once popular here in Cuba TV set, uses a very nice power transformer... so all the participants in the project began a search for those units. By collecting broken down PC computer power supplies, we were able to obtain the high voltage high capacity electrolytic capacitors, as well as ready-made line filters, high voltage diodes, transient suppressors and other parts. Now let me tell you that our UNIVERSAL TRANSCEIVER POWER SUPPLY is based on a design that yours truly published many years ago in the Radioaficionados magazine, that unfortunately is no longer printed... Soon we may be editing an ezine, an electronic edition, where one of the first articles is going to be, for sure, the detailed instructions on how to build the Super Islander Mark Six 40 meters band transceiver... In order to use the available parts, we adapted the design to whatever was at hand... For example the CFL Compact Fluorescent Light Bulbs circuit boards are home for a large number of high voltage silicon diodes, type 1N4007, that are rated at one thousand volts peak reverse voltage at one ampere... Combining the available ex TV power transformers with the high voltage silicon diodes from the CFL light bulbs and the big electrolytic filter capacitors from the computer power

6 supplies, we were able to obtain about 600 volts well filtered direct current at two hundred milliamperes, 250 volts at one hundred and fifty milliamperes, as well as negative bias voltage for the Super Islander's driver and final amplifier stages, that are both made using recycled vacuum tubes... More about this Boyeros radio club project in upcoming editions of Dxers Unlimited... And now amigos here is Arnie Coro's HF plus low band VHF propagation update and forecast... More Sporadic E events happening this week, but they are going to be less in number and will last for shorter periods as the end of the summer Sporadic E season is approaching. We continue to see the daily after local sunset enhancement of the frequency range above 10 megahertz and up to 18 megahertz, typical of the northern hemisphere summer season. The daily solar flux is hovering around 120 units, and scientists are keeping a close watch of several active sunspot regions showing magnetic complexity that may produce M- class solar flares. See you all at the mid week edition of Dxers Unlimited next Tuesday and Wednesday UTC days, and don't forget to send your signal reports and comments about our programs to inforhc at enet dot cu or Via Air Mail to Arnie Coro,Radio Havana Cuba, Havana, Cuba inforhc@enet.cu