Radio Habana Cuba: Dxers Unlimited Mid-week edition for December 12, 2000
By Arnie Coro, radio amateur CO2KK
Hi amigos, welcome to the mid-week edition of Dxers Unlimited, your favorite radio hobby program coming to you via short-waves... I am Arnie Coro, radio amateur CO2KK, your friend here in Havana, now ready to bring you about sixteen minutes of all radio hobby related information...
Here are the headlines: The solar minimum is OVER... from now on we will see the daily solar flux move UP until another peak of around 200 or more solar flux units is reached... Strap to your seat and get ready for some more action, as solar active region 9267 is growing at a fast rate and may generate big flares anytime now! Despite lower solar activity during the past 7 days, propagation conditions on the higher HF bands, from 20 megaHertz up continued to be pretty good. Even the 6 meter band brought some openings when the daily solar flux was low as 140 units...
Item three: The KKL-7, a non-resonant loop antenna for both amateur bands operation and short wave listening, brought a lot of feedback from Dxers Unlimited's worldwide audience. I will give more details here today, and have already sent via e-mail the text and graphic files that provide detailed information about this simple yet very effective antenna system for those of you who do not have a lot of space to install your skywires. The KKL-7 is just 7 meters on each side, that is roughly 23 feet, and when fed with either open wire line or the so-called window 450 ohm transmission line, will provide excellent coverage from as low as 7 megaHertz to up to 50 megaHertz, although it will be at its best between 10 and 30 megaHertz. The KKL-7 is a non-resonant loop, so it MUST, and I repeat this, MUST, be used with an antenna tuner. For those of you who did not tune in to the weekend edition of Dxers Unlimited, here again is the name of the antenna: the KKL-7, seven meters per side square loop. You can send for the text and graphic files by requesting them from arnie@radiohc.org, and I will e-mail them to you as soon as possible. Via AIR MAIL, a postcard request will be OK, and please don't forget to include your return postal address!!!
Stay tuned for more radio hobby related information... Margarita Delgado is my sound engineer and producer. This is Dxers Unlimited...
Amigos, your receiver is tuned to Radio Havana Cuba, thirty nine years on the air, at your service. On May the first of 2001, our station will celebrate its 40th birthday; yes, we are soon to reach fourty years of uninterrupted short wave broadcasting!
Here now is item three in today's edition of Dxers Unlimited... the very popular YOU have questions and Arnie tries to answer. The question today comes from a listener in California; by the way, he says that he tunes to 9820 kiloHertz with a good signal from 0500 to 0700 UTC, and that's the time when we have our curtain array beaming to the Pacific Coast of North America... Well, here is his question: Dear Arnie Coro, this has to do with battery power. You were right, when I disconnected my small digital portable from the wall wart or wall plug DC power supply and started operating the radio from the 6 volt gel cell accumulator, reception became much better!!! Now, I want to know how to charge the gel-cell accumulator properly, so as not to overload it...
Well amigo, that's a good question. Your best bet is to use a constant current charger, and set the charging rate to about one tenth of the current that the accumulator is rated. Then, monitor the voltage, keeping in mind that a fully charged 6 volt accumulator will show almost seven volts without any load connected to it!
And -- here comes an important piece of Arnie Coro's advice for all of you radio hobbyists -- IF YOU DO NOT OWN A DIGITAL MULTIMETER YET... don't wait any longer, get yourself one or maybe two of them. It is the most useful electrical measuring instrument that you can imagine. You will want to have a higher quality and more expensive one, but it is a good idea to buy a cheaper pocket digital multimeter too... With the digital multimeter, MONITOR the gel cell accumulator voltage, and when it reaches about 5 volts, it is time to recharge it. BUT PLEASE BE CAREFUL, and do not pass a lot of current, because a high current will certainly deteriorate the gel-cell. SO avoid using a car type battery charger. It is a very good idea to homebrew a simple constant current charger that can be built using any of the many existing circuit diagrams. It requires just a few readily available electronic components, and can be used to charge not only the gel-cell accumulators, but also nickel cadmium and nickel hydride batteries too...
For a nice 12 volts DC clean power source, just series connect TWO 6 volts gel-cell accumulators, and DO REMEMBER that they are sometimes available just for the asking or at a very low cost from people that provide service to intruder and fire alarm systems, because they must replace the gel - cell accumulators periodically, even if they are still in almost-new condition. My experience here with two of those accumulators is that they have provided power to my two meter, 5-watt power output handie talkie for the past two years without a single failure, and this power system offers the advantage, when float-charged with a trickle current, of being always ready in case of any emergency!
Hope this answers your question, and keep in mind that any time you connect a radio receiver to an AC power outlet, if your power supply is not a really professional one, with lots of filtering, some of the noise present on the powerline waveform will make its way to your radio... So the best way to avoid this is just to go to battery power full time... As a matter of fact, the dyed-in-the-wool AM medium-wave band Dxers first, and the LOWFERS or low-frequency band Dxers later, always try to run their receivers from battery power to improve the SIGNAL TO NOISE RATIO, all-important at those frequencies !!!
This is Dxers Unlimited's mid-week edition... and here is item four...more digital signal processing radios coming!!! Recent developments in digital signal processing now allow some manufacturers to start producing much lower-cost radios that use this advanced technology. The DSP radios do need a well=designed and built front end, but once the signal is converted to a low intermediate frequency, everything is totally different from the signal processing point of view. As a matter of fact, some of these radios, when you open them, show a rather empty box, because digital technology and sophisticated large scale integrated circuit make possible a very compact circuit board design. NOW, some of the DSP radio manufacturers are making public the source code for the software, and thus making it possible for users to develop their own applications...
If the DSP trend continues, we may soon see at least one portable about the size of the classic ICF2001, or ICF2010 as it is also known, incorporating digital signal processing at a low intermediate frequency... AND NO, I am not talking about another breed of radios that make use of YOUR COMPUTER to provide not only a graphical interface, but also a lot of the signal processing. What I am talking about is, in my opinion just around the corner, and may soon invade the short wave portable radio's high-end market with a very high quality receiver that, due to digital signal processing technology, can be produced at a reasonable cost. Just imagine having brickwall filters that range in bandwidth from maybe 500 Hertz to 10 kiloHertz, without having to use expensive crystal or mechanical filters at all!!! These digitally synthetized filters are already available on several of the DSP radios that do require the use of a computer interface, but may soon show up in a totally portable radio that will be certainly be a big hit among short wave listeners and amateur radio operators worldwide!!! And again, to make this clear, these radios can be mass produced at relatively low cost, due to the use of digital technologies!
Now amigos let's take a quick look at Arnie's workbench... wish you could see a photo of the workbench today... it is pretty crowded. The left side is in use by a 486 computer that I am just finishing assembling... it is an old DX2 66 mHz machine that will soon be running LINUX... The center of the workbench is full of all the parts and circuit boards for yet another version of the KK-ONE simple receiver and to the right, I have an experiment running! It is a very stable VFO, or variable frequency oscillator, using the cheapest possible components, and that so far has proven to work pretty well, due to the use of a) a very good voltage regulation of the power supply, and b) the use of the so-called COLD OVEN technology -- that is, using styrofoam thermal insulation to enclose the whole VFO. The theory behind this is that if you keep all the parts inside the oscillator at a constant temperature, even not-so-good capacitors and coils won't drift from their values. In other words, if the temperature inside the box does not change, the oscillator frequency will stay right where you set it!!! BUT, of course, the better the components you use, the better stability you achieve, and don't forget that building a VFO or variable frequency oscillator does involve a lot of very careful mechanical layout work!!! I hope to have the new version of the KK-ONE low-cost receiver ready by the end of the week, and will upload it to the website for all of you to have a look and maybe even attempt to build your own... Why not?
And now, as always at the end of the show, here is Dxers Unlimited's exclusive and not copyrighted Arnie Coro's HF plus 6 meters propagation update and forecast: SOLAR ACTIVITY moving up FAST... Solar active region 9267 is growing at a fast rate, and will soon be in a very geoeffective position, so if it starts to produce solar flares during the next three days as I expect, we may see some very interesting HF propagation events developing. Solar cycle 23 is, in my opinion, still moving towards its peak, to be reached sometime during the next six to nine months!!! So we may yet see a lot of sunspots, solar flares, high solar wind gusts, coronal holes and radiation storms during 2001!
Now, here is the forecast: Expect excellent HF propagation conditions to prevail on the bands from 14 to 30 megaHertz during your local daylight hours; the lower segment 14 to 18 megaHertz will show a propagation peak during your local sunrise and sunset. 50 megaHertz band amateur radio operators must be on the alert for possible F2 openings, and from now on, the winter solstice sporadic E season will provide some interesting DX to both 6 meter band operators and TV Dxers. Due to the rather low A index, the 80 and 40 meter bands will provide worldwide DX conditions during the local nighttime hours, too!
And don't forget, what makes Dxers Unlimited different is your feedback; take a little time, and e-mail me your comments about this show. Include your radio hobby-related questions too... and if you are not yet in cyberworld, please do send me an Air Mail postcard to Arnie Coro, Radio Havana Cuba, Havana Cuba... and don't forget to include your return address so that I can QSL back to you! See you all on 10 meters, on 28.5 megaHertz plus or minus 5 kilohertz, whenever the band is open and I am home!!!
Arnie Coro CO2KK
Havana, Cuba
December 12, 2000Postal address:
Arnie Coro, "Dxers Unlimited"
Radio Havana Cuba, Havana, CUBA
e-mail: arnie@radiohc.org
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