RADIO HABANA CUBA
DXERS UNLIMITED
MID-WEEK EDITION
TUESDAY, JUNE 5, 2001
By Arnie Coro CO2KKSend your comments, questions and ideas to: arnie@radiohc.org
Hi, nice to have you listening to the mid-week edition of Dxers Unlimited, your favorite radio hobby show on short wave and on our Dxers Unlimited website, and also available now via our exclusive Dxers Unlimited's mailing list.. I am Arnie Coro, radio amateur CO2KK, your friend here in Havana.
Here is item one: We are seeing a new solar rotation, and at least two sunspot groups have shown signs of complex magnetic activity... so be prepared for maybe more solar flares during the next 48 to 72 hours.
Item two: Lots of sporadic E openings, with the MUF climbing as far as the Aviation AM band 118 to 136 megaHertz...
Item three: Many Dxers Unlimited listeners that are subscribed to the e-mail distribution list are requesting the Regenerative Receivers INFO PACKAGE, so now, those who are already subscribed to the mailing list will be receiving the complete Regenerative Receivers INFO PACKAGE too. You can subscribe to the mailing list very easily, keep listening to this show, and in a few minutes I'll tell you how to do it...
Item four: Another source of parts for the budget radio amateur station... Practically all modern telephones use an electret condenser microphone, which very rarely fails, even after the telephone set has seeing many years of service... The condenser microphone provides a high quality audio, and it only requires a very simple setup to operate... SO... add old telephones to the list of equipment from which you can recycle components, including the electret condenser microphones....
Item five: Early morning Tuesday local time here in Havana, the 90 meters Tropical Band was wide open... at least three stations were coming in with an SIO of 555.... Check the 90 meters band during the next several mornings, do it about an hour before sunrise, and start scanning from 3200 kiloHertz slowly up, you may find some interesting DX there... Now stay tuned to this frequency, Margarita Delgado my sound engineer and yours truly Arnie Coro will be back with you in a few seconds...
This is the mid-week edition of Dxers Unlimited... you can send your radio hobby related questions, signal reports, QSL requests and comments about our programming via e-mail directly to my computer at: arnie@radiohc.org, or if not yet in cyberspace, send your Air Mail letter or postcard to Arnie Coro, Radio Havana Cuba, Havana, Cuba...
Now here is item six: The ever-popular, la numero uno, the section of Dxers Unlimited that receives more e-mail messages and letters than any other one... Here is YOU HAVE QUESTIONS, and Arnie Coro tries to answers them...
Today I'll answer three questions sent in by listeners via e-mail. Here is the first one:
Arnie, I am just starting to homebrew radio and electronics gear, just finnished a very simple crystal radio... now I want to add more audio amplification... Any advice?
Well, amigo you can add many different types of audio amplifiers to your homebrew crystal set... from an ultra-simple one-transistor audio stage powered by a 9-volt battery, to a sophisticated multi-stage audio amplifier... My advice is to try building a simple two- or three-stage transistor audio amplifier that can be powered from a single 9-volt battery, or from three or four type AA batteries... The audio output will be more than enough to require lowering the volume control on many stations... You can also try a nice combination that I like very much, a low-noise transistor single-stage audio amplifier coupled to an integrated circuit like the LM380, LM386 or more modern versions of those two... As a matter of fact, I have made about ten of those, as every time an audio amplifier stage is required, this is my favorite circuit. For high-impedance input, I simply add a low-noise field effect transistor operating so as to provide only an impedance transformation and no gain...
OK... now here is question number two... it came from a listener in Mexico and he wants to know if the KK40-dash 15 antenna needs ground radials.
Well amigo, I would certainly add no less than 4 radials at the near-to-the-ground end of the KK 40-15 dual band sloper directional antenna system... All the tests done here show that the antenna works a lot better, especially on the 15 meter band, when the set of no less than 4 elevated quarter wave radials are added... And yes, you can install up to three KK 40-15 antennas using a single mast... Each of the three antennas slopes into a different direction, and you can switch between. The front-to-back ratio of this system is not very high, but it is certainly much better than what's provided by a dipole.... And here is the question number three: Arnie, how can I learn how to solder electronic components?
AH... that's a very good question, my friends!!! You will need a lot of patience and dedication to learn how to solder electronic components properly... and the quality of whatever radio and electronics gear you homebrew or repair will be always directly related to how well you do your soldering! The best approach is to learn from someone who really knows how to do it.... and then practice, and practice, and practice... One of the worst mistakes made by beginners is to forget how important it is first to properly clean the parts to be soldered... the slightest trace of oxides will lead directly to a poor solder joint, one of the worst nightmares that one can deal with while trying to repair radio gear or make it work for the first time.... Si, yes, oui amigos... You will need a high-quality thermostatically controlled soldering iron, high quality solder, which today means not only tin and lead, but also about 2 percent silver added... very clean parts and the know-how to solder properly.
It will take some time, but once you master it, it is going to be a very, very rare occasion when your soldered joints won't work properly... so-called cold soldered joints are one of the homebrewer's worst enemies!!! AH... and before leaving this topic... do remember that the typical soldering iron developes high temperatures that may cause really bad burns and even start a fire, so always be extremely careful when soldering, and never forget to turn off the soldering iron before going away... As a matter of fact, a very good idea is to have a circuit breaker installed at your workbench, or if you don't have a workbench yet, use an extension cord that has a switch, so that you can be really sure that it will be switched off when you end the soldering session...
Si amigos, you can subscribe to our Dxers Unlimited's mailing list... the process is a very easy one... just send a message to MAJORDOMO at rhc.cu, leave the subject line blank, and in the body of the message type the following: subscribe dxers_l, that is the word subscribe, a space, then dxers, underscore, and then the letter l like in LIMA....Majordomo will send you a confirmation of subscription and the instructions on how to unsubscribe when you wish to do so...
Now here is item seven: As I said at the start of the show, modern telephones do use a high-quality electret microphone... it is an ideal mike for your homebrew amateur single side band, FM or AM rigs... And of course, coming from a discarded telephone, it will cost you nothing... There are two types of electret microphones that are used by typical telephone sets -- one has two terminals, and the other type has three terminals. The two-terminal type just requires a voltage source via a resistor, and a capacitor to couple the audio output... The three-terminal electret microphones may require one resistor to feed the voltage, a capacitor to couple the audio to the first pre-amplifier stage, and a ground terminal.
A homebrew microphone made from the electret capsule used by a telephone will require the use of shielded flexible audio cable, known as microphone cable, and you will have to use a battery to power the field effect transistor that is inside the electret microphone capsule... The battery can be housed inside the microphone's case, and you may want to add a small switch, to switch off the battery when the mike is not in use.... The discarded telephone will also provide many other parts for your electronic projects, so once you finish removing the electret microphone capsule from the handset, don't send the rest of the telephone to the recycling plant without removing each and every electronic component, and the screws, nuts, washers, etc. YES, AMIGOS... you can enjoy the radio hobby on a shoestring budget...if you know where to look for the parts needed. If you ever happen to pick up CO2KK, my amateur radio station, your chances are high that you will be listening to one of these homebrew electret microphones, recycled from old telephones!!!
This is the mid-week edition of Dxers Unlimited, and for those of you who are not yet in Cyberspace, here is our Postal Mailing Address... send your AIR MAIL postcard or letter with your signal reports, comments about the show, and QSL request directly to me: Arnie Coro, Radio Havana Cuba, Havana, Cuba.
And now, just before going QRT, get ready to copy Arnie Coro's Dxers Unlimited's exclusive and not copyrighted HF plus 6 meters propagation update and forecast... Solar activity is still low, but may move to moderate during the next 48 to 96 hours... Two solar active sunspot regions are possible sources of M class flares that may be happening during the rest of the week... Solar flux is moving UP, and on Tuesday morning was very near 160 units, while the A index was between 12 and 15, indicating a slightly disturbed geomagnetic field. The daily sunspot count was 125, down from Monday's 143, and Sunday's 141, but this may change tomorrow... The effective sunspot number, the figure you will like to use for calculating HF propagation with your computer, is very near 110... The 3000 kilometer F2 MUF was around 35 megaHertz on the best paths Tuesday morning.
My forecast calls for plenty of Sporadic E openings during the next 10 days... so watch those FM broadcast band empty channels, and if you already happen to have a 6 meter band amateur transceiver, keep it scanning from 50.0 to 50.2 megaHertz, and if it does not have the scanning facility, then tune it to 50.125 in the Americas or 50.110 in Europe... DOnt' forget to send me an e-mail to arnie@radiohc.org if you enjoyed today's edition of Dxers Unlimited... it is always very nice to hear from you, amigos!!!
Arnie Coro CO2KK
Havana, Cuba
June 5, 2001Postal address:
Arnie Coro, "Dxers Unlimited"
Radio Havana Cuba, Havana, CUBA
e-mail: arnie@radiohc.org
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