DXERS UNLIMITED
WEEKEND EDITION
SATURDAY, MAY 12, 2001
By Arnie Coro CO2KK
Send your comments, questions and ideas to: arnie@radiohc.org
Hello, amigos! Welcome to the weekend edition of your favorite radio hobby program, now available via three different distribution modes... On the air, via Radio Havana Cuba's short wave transmitters, on the World Wide Web where you can read these scripts in HTML format by visiting our Dxers Unlimited website, and you can also subscribe to our Dxers mailing list and the script of every show will be sent to your computer via e-mail. Now, as we changed from a text format to an HTML format, the script also may include some very useful graphics too!
Here is item one for today's show: A geomagnetic disturbance caused by the charged particles coming at high speed from a solar coronal hole sent the K index shooting up to 5 around noon my local time here in Havana; that is at this time of the year, due to the use of Daylight Saving Time, 16 hours UTC.
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The Solar Coronal Hole You are actually viewing the area where the solar corona has a hole in it that is letting high-speed charged particles out into space. When those particles hit the Earth's magnetosphere, then a geomagnetic disturbance starts. To generate a disturbance, the coronal hole must be located pointed at the Earth in what scientists describe as a "geoeffective" position which is the case with this one.
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Item two: In a few days, the Hurricane Season will start here; amateur radio plays a vital role in providing much-needed emergency communications during tropical storms and hurricanes, that's why I will tell you today about an interesting finding that came I across when we changed our radios here to more modern ones!
Item three: Yes, building your own radio receiver may sound too difficult for beginners, but with the help of a more experienced hobbyist, you can certainly homebrew a nice radio receiver... And you know, amigos, they somehow seem to sound better to your ears than the factory-built radios!!!
Stay tuned for more radio hobby related information, coming to you from Havana... Margarita Delgado is my sound engineer and producer... I am Arnie Coro, back with you in a few seconds...
You are listening to Radio Havana Cuba, forty years on the air, at your service! This is Dxers Unlimited's Weekend Edition, and here is item one in detail:
In a few days, the official yearly Hurricane Season will start here. It runs from the first day of June to the last day of November, and amateur radio operators in Cuba always participate in several emergency drills before the month of May comes to end, just to see how all the communications gear is working... Now let me tell you about something we found out -- the hard way, I must say -- when the equipment used for the Hurricane Emergency Net was changed from analog frequency dials to the modern solid state digital displays... Listen carefully, this may help you in case sometimes your amateur radio station has to be operated under similar conditions as the ones I will describe now!
Every time we experience torrential rains here in the Caribbean, radio amateurs and short wave listeners are very clearly reminded that modern radios do not like high humidity at all... Many of those participating in emergency nets have to keep light bulbs and fans blowing hot air into their radios to be able to read the liquid crystal displays!!! And yes, that's the way to go, keep the radio as far away as possible from aerosols, and blow hot air into the cabinet to remove the humidity that causes the problem. Then, keep the radio on all the time, if that is possible, to avoid the possibility of further condensation. Humidity is a real big enemy of electronic equipment, especially where high voltages or very closely located circuit board patterns are involved.
You are listening to Radio Havana Cuba, the name of the show is Dxers Unlimited, and YES, this is a program devoted to both beginners and experts, and dealing with topics related to the more than 50 ways that you and I can enjoy this wonderful hobby... RADIO!!!!
You can send your QSL requests direct to me: e-mail to arnie@radiohc.org and via Air Mail, to Arnie Coro, Radio Havana Cuba, Havana, Cuba.
Here is item two: And YES, amigos, my friends, I do insist: building a regenerative receiver is a once-in-a-lifetime experience... Even an ultra-simple circuit with a very low parts count will give you not only the pleasure of listening to the your local AM broadcast band stations, but also the possibility of picking up some nice DX. There are two secrets when building regenerative radios that can't be forgotten: Build them like a battleship, and experiment with the bandspread tuning. My two-vacuum-tube regenerative radio has an excellent bandspread on both the 80 and 40 meter bands, something that allows me to tune DX stations easily. Selectivity-wise, the regenerative is hard to beat, especially when you are able, very carefully, to take the circuit very close to the point of oscillation.... Among my latest DX stations on 40 meters. picked up using the 2-vacuum-tube regenerative, are several Pacific Islands, India, and Middle East stations, using a 10 foot long -- or about 3 meters long -- wire antenna that drops down through the window!!!
AH... the vacuum tubes, before I forget: they are a 12AT7 or ECC81 that acts as grounded grid radio frequency amplifier and regenerative detector, and a triode pentode removed from an old TV set, the ECL85, which provides ear-shattering or room-filling volume, depending on whether you are using headphones or a loudspeaker. The power supply uses a one-to-one AC power line isolation transfomer, and provides about 150 volts DC to the vacuum tube anodes, and I wound an extra secondary to provide 6.3 volts for the filaments.
This little radio is a wonderful to promote interest in amateur radio and short wave listening among friends.... And parts for it can be found at very low cost or sometimes just by recycling old radio and electronic equipment that may be gathering dust somewhere... INTERESTED??? SURE!!! Then e-mail your request for Arnie Coro's REGENERATIVE RECEIVERS INFO PACKAGE to arnie@radiohc.org. And if not you're yet in Cyberspace, it will just take a little longer; send your request via Air Mail to Arnie Coro, Radio Havana Cuba, Havana, Cuba...
This is Radio Havana Cuba's Dxers Unlimited, the one and only radio hobby program with the most up-to-date HF plus 6 meters propagation updates and forecasts.... Even if you listen to our late late late show Havana time, sent to the Pacific Coast of North America and beyond, the propagation forecast is never more than 12 hours old....
Now amigos, let's take a very short visit to Arnie's workshop, just to remind you about something Arnie Jr. learned this Saturday: Arnie Jr., my eldest son, is assembling a computer, and he came to pick up some components I had for him... then he asked why I had included so many split ferrite cores in the box. The reason, Arnie Jr., Arnaldito or little Arnie -- never mind he's 6 feet, 2 inches tall and weighs some 200 pounds, but you know, amigos -- the kid is always the kid... Well I told my boy the reasons why I had included the ferrite split cores in the box with the other computer parts... "Arnaldito, you are going to use your new machine with your ham radio station, and it is good engineering practice to include as many split ferrite cores as possible on all cables that enter and exit the computer's case.... Keep that in mind, the more RF-stopping split ferrite cores you add, the better... and don't forget to install additional ones on the cables going to the monitor, too!!!" Ans that is what he has done, and it's is making his CM2KW radio amateur digital station work a lot better than if he had not followed his dad's advice about the ferrite cores RF chokes!
And now amigos, as always at the end of the show, here is Arnie Coro's HF plus 6 meters propagation update and forecast: No less than 6 active solar sunspot regions could be seen Saturday morning here from my optical observation post here in Havana, but not one of them has a really complex magnetic configuration. The official sunspot count is a bit less than 100 and it is moving up. If you need to run propagation forecasting software for a particular path, then use 100 sunspots as the number provided to the program to make the calculations.
Best nighttime reception will be in the region between 10 and 16 megaHertz, but you will notice that both the 20 meter amateur band and the 19 meter broadcast band will fade away and close around mid-evening local time... Both the 31 and 25 meter broadcast bands from 9 to 12 megaHertz are the best ones for nighttime reception. We must wait until the ongoing propagation disturbance comes to an end for the HF bands to recover, something that should be happening by Tuesday.
Super J-Pole Antenna
For those of you who wanted to know more about theSuper J-Pole Antenna --
a long-lasting version, made with copper plumber's pipe -- here is a nice
diagram of an antenna designed for the 2 meter amateur band. It has about
6 DB gain over a dipole, and is omnidirectional, meaning that it radiates
equally well in all directions:
