Radio Habana Cuba: Dxers Unlimited Weekend Edition for 14 August, 1999
By Arnie Coro, radio amateur CO2KK
Hi amigos! welcome to the weekend edition of your favorite radio hobby show on shortwave. I am Arnie Coro, radio amateur CO2KK, your friend here in Havana, and host of this twice weekly RHC program devoted to the promotion and enjoyment of our wonderful hobby, yours and mine... RADIO.
Here is item one: Solar activity MINIMUM reached this week, a dramatic drop in the number of sunspots and solar flux... BUT, get ready for a new peak in solar activity to be reached by the end of the month!
Item two: for those of you that enjoy listening to foreign broadcasts in the station's own national language... Radio Havana Cuba's Spanish language broadcasts can be heard on both 6000 kHz and 9820 kHz from 00 to 01 hours UTC, just one hour BEFORE our regular daily English language broadcasts to North America start... And, for those of you in North America that want to practice your Spanish a bit more, listen to our 9550 kiloHertz frequency from 00 to 05 hours UTC, which is beamed to the East Coast of North America from Georgia and the Carolinas up all the way to Northern East Canada.
Item three, the rest of the menu: Arnie's workshop answering a question about an expanded scale voltmeter, which is a very convenient test instrument you can build yourself, the Perseids Meteor Shower fiasco for most of the world, more about the Solar Eclipse, and as usual, at the end of the show, Arnie Coro's exclusive, easy to understand, plain language, free for all, in the public domain HF propagation update and forecast. Stay tuned, I am sure you are going to enjoy listening to the weekend edition of Dxers Unlimited...
Yes, your signal reports and comments about the show are most welcome... send them directly to me, via AIR MAIL. Here is the address: Arnie Coro, Radio Havana Cuba, Havana Cuba. Si amigos, yes my friends, oui mes amis, as easy as that, thanks to our nice friends at Havana's main post office, you need to just write this very simple address: Arnie Coro, Radio Havana Cuba, Havana Cuba... and via INTERNET it is also a very easy one too; mail to: arnie@radiohc.org, and our URL is www.radiohc.org. Go there, and click on Dxers Unlimited's webpage to enjoy reading the scripts of the show, and get all the files about antennas, receivers, transmitters and propagation available for your free and fast downloading.
Now item four: Another visit to Arnie's workshop... today I will answer a question sent in by a listener in the United Kingdom. Here is the question: "Arnie, is there any way to make a DC voltmeter measure just the critical operating area of my batteries, that is from about 10 to 15 volts, instead of using the full scale for the 0 to 15 volts???" Sure amigo, and this is known in the trade as an EXPANDED SCALE VOLTMETER. I must say that it is one of the most useful and practical instruments that one can think of. For example, as you well know, the most popular type of storage batteries are so-called 12 volt types. If they are made by series-connecting lead acid cells, six of them in series connection will provide, when fully charged, 2.2 volts times six, so here it is 13.2 volts. But in order to CHARGE that battery, the charger must provide no less than 14 or better yet 15 volts DC. Here is how an EXPANDED SCALE VOLTMETER helps you a lot. You design your meter so that the extreme left end of the scale, instead of reading 0 volts as usual, reads say 10 volts, and then the extreme right or maximum is made to read 15 volts or 16 volts. This is easily achieved by using a very simple circuit requiring just 2 fixed and one variable resistors and a zener diode... and of course the METER itself.
ARNIE'S EXPANDED SCALE VOLTMETER Parts List: For my EXPANDED SCALE voltmeter, I use a standard 0 to 50 microampere meter movement, a 2.7 kilo-ohm resistor, a 68 kilo-ohm resistor, a 22 kilo-ohm pre-set type potentiometer or variable resistor, and a 10-volt zener diode. If you cannot find a 10-volt zener diode, just go ahead and use a 9.1 zener diode; for some some reason, these are much more easily available. If you use the 9.1 volt zener, then your meter scale will go from 9 to 14 volts and the 15 volts will probably fall off scale, right at the end of the scale, but still useable. As you may realize, NOW you have a meter that really HELPS to SEE how much voltage the battery is really delivering. Your meter will measure from 9 or 10 volts to 14 or 15 volts, so you can tell when the battery REALLY needs recharging, without having to resort to the digital multimeter. As a matter of fact, I use several of these expanded scale voltmeters in my equipment.
Now here is how to interconnect the components of the expanded scale voltmeter. If you have any doubts, just go to www.radiohc.org, download the script of this show, and read it carefully, OK? Here we go...
Assembly: The meter's PLUS terminal connects to the PLUS terminal of the battery you are monitoring. From the meter's PLUS terminal, you connect one lead of the 2.7 kilo-ohm resistor. The other end of the 2.7 kilo-ohm resistor goes to one lead of a 68 kilo-ohm, 5 percent tolerance resistor. The other end of the 68 kilo-ohm resistor goes to one terminal of the 22 kilo-ohm variable preset resistor. The two other terminals of the 22 kilo-ohm preset resistor are connected together and, with a wire, to the MINUS terminal of the meter. Now you connect cathode end of the 10 volt or the 9.1 volt ZENER diode to the junction of the 2.7 kilo-ohm resistor and the 68 kilo-ohm resistor. The ANODE of the ZENER diode is connected to the MINUS TEST LEAD of the meter. Again -- this is important -- the PLUS test lead of the METER goes directly to the PLUS TERMINAL of the meter itself. But the MINUS TEST LEAD is connected ONLY to the ANODE terminal of the ZENER DIODE.
Calibration: The calibration is fairly simple... connect a DIGITAL MULTI METER to the battery that you want to test... measure the voltage, and then connect your EXPANDED SCALE VOLTMETER to the same battery at the same time. Let's say you have a voltage of 12 volts. Then, turn the pre-set control until the 50ua movement gauge is about mid scale... The final adjustment is done by using a variable power supply set for 10 volts. This should cause the gauge's needle to move to the low end of the scale. Now, carefully crank up the power supply's voltage and mark your scale at the 11, 12, 13, 14 and 15 volts and that's it. You are the proud owner of an EXPANDED SCALE VOLTMETER. Again if you have any doubts, just go to www.radiohc.org and download today's script. Read it carefully and draw the circuit from the description in the text. If you have any doubts, just write to me, mail to arnie@radiohc.org or send airmail to: Arnie Coro, Radio Havana Cuba, Havana Cuba.
You are listening to the weekend edition of Dxers Unlimited, and here are some comments about the very disappointing Perseids Meteor Shower... both astronomers and radio amateurs seem to agree that the number of meteors this year was much lower than in the past several years... Yes, it was a disappointing experience for many who spent hours and hours trying to make meteor scatter contacts on the 2 meter and the 1.25 meter amateur bands. And now some news about the solar eclipse: As expected, low frequency propagation did change during the eclipse, with some BIG signals heard from the several test transmissions organized for research purposes. Scientists are now processing data gathered during the eclipse, including some very interesting photographic plates of the solar corona, and recordings from several radio telescopes tuned to specific frequencies. All in all, this was a nice week for radio science worldwide, and the radio hobby got a lot of publicity, as newscasters mentioned many times the radio-related experiments that took place during the solar eclipse.
And now amigos, just before going QRT here, as usual, Arnie Coro's easy to understand, in the public domain, freeware HF propagation update and forecast! Solar activity will start moving UP again starting maybe today or tomorrow. Expect rather normal for the time of the year propagation during the next three to five days. BEST daytime reception of short wave international broadcasts will be found -- no doubt on this one -- on the 16 meter band, spanning from approximately 17.6 to 18 megaHertz. This is THE band to listen to from about 9 am your local time to about 6 pm your local time. Earlier, from about 6 am local time to 9 am local time, the 15 to 15.6 megaHertz or 19 meter international broadcast band will bring in nice signals. Get ready for very nice propagation conditions to come by the end of the month -- with possible solar disturbances, that's true -- but also with much higher Maximum Useable Frequencies to enjoy!!! Keep your nighttime reception optimized from 9 to 16 megaHertz, as the 5 to 9 megaHertz region continues to be very noisy due to summer thunderstorm activities.
Once again, any questions you have about the radio hobby, just e-mail to: arnie@radiohc.org and via AIR MAIL, send your comments to to Arnie Coro, Radio Havana Cuba, Havana Cuba.
Arnie Coro CO2KK
Havana, Cuba
14 August, 1999Postal address:
Arnie Coro, "Dxers Unlimited"
Radio Havana Cuba
PO Box 6240, Havana, CUBA 10600
phone: 53-7-814243
phone res: 53-7-301794
e-mail: arnie@radiohc.org
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