RADIO HABANA CUBA
DXERS UNLIMITED
WEEKEND EDITION
SATURDAY, JUNE 30, 2001
By Arnie Coro CO2KKSend your comments, questions and ideas to: arnie@radiohc.org
Hi, amigos! Great to share with you the next seventeen and a half minutes of air time... I am Arnie Coro, your friend here in Havana and host of this twice-weekly radio hobby program brought to you courtesy of Radio Havana Cuba....
Here is now item one: BBC World Service apparently will not stop from canceling their broadcasts to North America, Australia and New Zealand... and Radio Nederland affirms that they will take up the frequencies that BBC is vacating....
Item two: A very unusual solar event in progress and nobody seems to be aware of it.... My good friend Angel Gonzalez Coroas of the Cuban Ministry of Science and Technology called me on the phone and alerted me about two group of sunspots that are located in the Sun's southern hemisphere at a very, very rare high latitude position... According to Angel, a long-time observer of solar events, these two groups deserve a lot of attention from scientists, as they may be signaling that something is happening 93 million miles away from Earth...
Item three: More and more radio hobbyists are learning to enjoy different aspects of this wonderful hobby... and one of them, of course, is building your own equipment... something that provides the additional reward of working with homebrew equipment. Friday evening at almost three o'clock in the morning I was listening to a two-way QSO, an amateur radio contact between a station in Texas and another station located in England... the British station was just running 2 watts to a homebrew transceiver, and his signal was a solid 569 here in Havana, while in Texas he was 559... Figure out the miles per watt and you will realize why I am telling everyone in my H.F. propagation forecasts that the 20 meter band is in top shape during this summer season, from just after local sunset to about an hour after local sunrise...
Item four, coming up in a few seconds after this brief musical interval... My sound engineer and producer today at RHC's studio number 6 is Jose Costa Pupo, I am Arnie Coro, stay tuned...
You are listening to the weekend edition of your favorite listener-oriented radio hobby program on short wave... admittedly one of the few that is still on the air, as soon we are going to hear the last broadcast of Radio Sweden's Media Scan show... but don't worry, we will continue on the air as always, offering a well-balanced menu of all radio hobby-related topics, and if you happen to want to hear about a particular topic, just drop me an e-mail to arnie@radiohc.org...
And now, here is item four... When building radio and electronic equipment at home, a lot of care must be exercised regarding two vital aspects: First you must know how to solder electronic components really well, and second you must TEST each and every part BEFORE soldering it in place. Following those two simple rules will save a lot of headaches... like the one my young friend Alberto had after finishing wiring up his two-vacuum tube regenerative receiver and power supply. He brought it to my workshop and after about half an hour of detective work, we found out that the volume control potentiometer had a broken internal connection... so the radio had no audio at all!!! He had tested the power supply, and that was OK, he heard the regenerative detector's typical swooosh sound in another receiver, but he had no audio. Following the standard working-backwards procedure, we found the bad volume control potentiometer, and now Alberto is enjoying his nice two tube regenerative receiver that he has assembled using recycled components... See, he forgot to test the volume control potentiometer with an ohm meter before installing it, and that led to the problem.
By the way, for those of you interested in learning more about this really simple, yet very effective AM band and short wave receiver... I have prepared a text file with the full description of how it works, and the complete circuit schematic diagram is included in the same document... The regenerative two tube radio circuit diagram and text file is available free of charge just by sending an e-mail to arnie@radiohc.org or a postcard via AIRMAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba, and don't forget to specify that you want the two tube radio circuit diagram and text file.
And for those of you who have asked for it... a solid state version of this receiver is now in the works here, so soon it will be available, too. This solid state version uses three types of active electronic devices, field effect transistors, bipolar transistors and two integrated circuits.
Now item five....Answering a question sent in by a listener from Florida: Yes, amigo, you are absolutely right... a direct lightning hit can destroy electronic equipment that is not connected to anything... Now if you want to know why, here is the answer: The huge electromagnetic pulse that is generated by the tremendous currents involved during the lightning event can and do destroy devices that are not connected to the power lines or antennas or ground systems... Electromagnetic induction is the culprit, and yes, I have seen it happen a number of times here in Cuba, where thunderstorms are almost as frequent as in Florida. A computer that was completely disconnected from all external sources of power or phone lines had its motherboard completely damaged beyond repair due to the electromagnetic pulse generated by a lightning stroke that hit a building in downtown Havana a few days ago.... And, as expected, damage extended to every light bulb in the house, the water pump, the TV set and VCR plus all radio receivers!!!
You are listening to Radio Havana Cuba, the name of the show is Dxers Unlimited... and here is Item Six: Do remember to disconnect all radio and electronic equipment after you finish using them... and when a thunderstorm is near, it's good practice to disconnect all your refrigeration equipment too, as lightning-induced power surges do damage the motocompressor units of refrigerators and freezers. OK, not radio hobby related this one, but still a valuable bit of advice... Isn't it?
Item seven: Here is the ever-popular antenna topics section of Dxers Unlimited... If you already have obtained your amateur radio license, chances are high that among your ham radio equipment there is at least one handheld FM 2-meter transceiver or handy-talkie... Two meters happens to be the most-popular and most-used amateur band worldwide, according to a recent survey, and the 2 meter FM handheld radio is also the most popular piece of ham radio equipment... and a very useful radio when any kind of emergency arises...
As many of you listening to this show know well, cell phone systems usually go dead when there is a big emergency in progress... the cell phone network simply overloads and quits working, something that never happens to amateur radio simplex communications, and very rarely occurs to ham radio repeaters... Well, it happens that many 2 meter band FM handy talkies come with a very inefficient helical antenna, which is known among hams as the "rubber duck." Replacing your 2 meter handy talkie's rubber duck with a simple easy-to-build 3/8 of a wavelength telescopic whip will improve your radio's coverage tremendously... You will only need an appropriate antenna male connector, usually a BNC type in older handy talkies, and a telescopic whip that can usually be found sold as a replacement unit... The telescopic whip must be extended to a length of about 56 centimeters to achieve maximum efficiency, but you can optimize its length for the particular frequency of your local repeater by using a field strength meter to see at what length the antenna radiates best... Any questions about the 3/8 of a wavelength telescopic antenna for 2 meter FM handy talkies? Just send them directly to my e-mail account, arnie@radiohc.org, or via AIRMAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba, and I will answer back as soon as possible. Keep your handy talkie always ready to deal with an emergency ... keep at least one battery fully charged and if possible have a second standby battery also ready for action, too!!!
Dxers Unlimited coming to you from Havana.... here is item seven in today's weekend edition of the show... You have questions and Arnie tries to answer them... This question sent in by a listener in Canada: he was having a lot of trouble with a homebrew 12 volts DC power supply using a three terminal voltage regulator... As soon as I received his request for advice I sent him an e-mail that said, "Amigo, please check that the bypass capacitors at the input and output of the 7812 voltage regulator are installed as close to the terminals of the regulator as possible... Your power supply may be oscillating." And, sure enough... a day later he replied, telling me that his supply was working nicely after he soldered the 0.1 microfarad bypass capacitors really close to the voltage regulator input and output pins...
So next time you are building a voltage regulated supply using these devices, don't forget to solder the bypass capacitors really close to the input and output pins, and here is another bit of advice: Use the highest possible quality, low inductance capacitors to assure best operation of the power supply.
And now, as always at the end of the show, here is Arnie Coro's exclusive and not copyrighted, in the public domain, free for the use of radio hobbyists worldwide... HF propagation PLUS update and forecast: Solar activity was moving down and will now probably start slowing moving up again this week, BUT beware... we may see the effects of the solar wind coming from a coronal hole during the weekend. Then, the rest of the week will probably register a period of very quiet geomagnetic conditions with the solar flux hovering around 150 units or so. Due to the summer thermal expansion of the ionosphere, best conditions for Dxing will continue to start near local sunset, and continue until about an hour after local sunrise... BUT daytime DX via sporadic E is very probable during the next two weeks, too...
See you at the mid-week edition of the show, next Tuesday and Wednesday UTC days, and don't forget that your signal reports and comments about the show are much appreciated; send mail to arnie@radiohc.org and postcards via AIRMAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba!
Arnie Coro CO2KK
Havana, Cuba
June 30, 2001Postal address:
Arnie Coro, "Dxers Unlimited"
Radio Havana Cuba, Havana, CUBA
e-mail: arnie@radiohc.org
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