RADIO HABANA CUBA
DXERS UNLIMITED
MID-WEEK EDITION
TUESDAY, AUGUST 28, 2001
By Arnie Coro CO2KKSend your comments, questions and ideas to: arnie@radiohc.org
Hi, amigos radioaficionados around the world! This is the mid week edition of Dxers Unlimited, your favorite radio hobby program, coming to you via shortwave from Radio Havana Cuba! I am Arnie Coro, radio amateur CO2KK, your friend here in Havana, and here is the menu for today:
Solar scientists are enjoying a very interesting period of solar cycle 23... the second most powerful solar flare of this cycle last Saturday provided researchers with a lot of valuable data in their never-ending quest to try to learn more about the Sun... The X5 type solar flare also generated a high speed solar wind gust that passed the Earth on Monday... and YES, me may see more flare activity from solar active region 9591 during the next few days....
Item two: Compact antennas are essential to those that have very little space to install them, and also to short wave listeners and amateur radio operators who have to face the reality of zoning laws and covenant restrictions at apartment buildings and condominiums... That's why a small, two-element Yagi type beam antenna that I will describe here today is becoming so popular...
Item three: Recycle, recycle, recycle... sure, recycling electronic components is a lot of fun, and there is the great pleasure of having those parts that had a tag marked "destination: dump" used in your homebrew radio projects... Now I found yet another source of electronic components waiting to be recycled... first and second generation FAX machines, and they also have lots of mechanical parts that can find manyinteresting new applications when you are building your radio equipment at home...
The ever-popular "you have questions and Arnie answers them," or at least I try... will also be part of today's show, as well as our HF plus 6 meters propagation update and forecast at the end of the show... Stay tuned, this is Dxers Unlimited, the friendly radio hobby program with you the listener always in mind...
The name of the station is Radio Havana Cuba, the name of the show is Dxers Unlimited and YES amigos, we do QSL one hundred percent here...Send your QSL requests via AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba, and don't forget to include the frequency, date and time you heard our station, as well as some comments about the program. Via e-mail we can be reached by sending your signal reports and comments to arnie@radiohc.org.
Now here is item two: How small can a YAGI type antenna be, and still provide useable directivity, front to back ratio and lower take off or departure angle??? Well that is a very good question, one that antenna gurus would certainly enjoy talking about a lot... By using the most up-to-date antenna analysis software, experimenters have built several very compact two element Yagis that use a combination of both inductive and capacitance loading... For example, a two-element beam for the most popular amateur HF DX band, twenty meters, can fit into a boomlength of two meters or even slightly less, and the elements can be made so that the antenna will have "the look" of one used for low band TV reception. Of course, these ultra-compact antennas do require complex mechanical construction work, and their effective bandwidth is much smaller than a standard full size two element twenty meter band Yagi.... but, amazing as it may sound, and precisely due to the use of the most up-to-date method antenna analysis software, the ultra-small two element 20 meter beam can provide its user with about 3 dB gain over a dipole or even slightly more!!! And, there is even the possibility of designing a three band ultra compact two element Yagi for 20, 15 and 10 meters using the same combination of inductive and capacitive loading of the elements.
One of the most interesting facts about two element Yagi antennas is that they are so effective in improving HF ionospheric communications, due to the fact that they provide three important advantages over a standard half wave dipole... Number one: Increased directivity, that is, a forward gain of no less than 4 dB over a dipole for a full size antenna; Number two: Increased front-to-back ratio, even when using small loaded elements; and Number three: The two element Yagi, be it a full size or a compact version, when properly installed, will always provide its user with a lower take off angle, something that produces what could best be described as an "additional gain," due to the fact that the signal departs towards the ionosphere at a lower angle...
So amigos, if you already are the happy holder of an amateur radio license and want to add enjoyment to HF operation, think about the nice possibilities that a commercially built or homebrew two element Yagi can provide. Here at CO2KK, my own amateur radio station, I have used simple WIRE TWO ELEMENT YAGIS for years, hanging them from wooden or bamboo or fiberglass spreaders... My wire two element Yagis have always been full size, but maybe when the solar cycle starts to reach rock bottom figures, I will attempt to design a two element 40 meter compact wire beam!!!
Have you seen a retired FAX machine lately? They were very well built, and are a treasure chest of both mechanical and electronic components. Due to the low level of integration at the time those early FAX machines were designed and built, they will provide you with a lot of easily removable components... Among parts that those FAX machines have are power transformers, as the earlier models did not used today's switched mode power supplies. You will find nice power diodes and power transistors and a myriad of resistors and capacitors, but let me warn you about one specific type of capacitor that must be approached very carefully when attempting to recycle it:
Electrolytic capacitors must be tested for leakeage before recycling them... High quality electrolytics have a very long life span, but others may dry up and then will measure much lower capacitance values than the value marked on the body of the capacitor. In other words, when recycling electrolytic capacitors from old equipment you must be very, very careful, in order to avoid problems that may be difficult to diagnose once your homebrew equipment is finished.
Old FAX machines also have lots of mechanical components that can be used in your homebrew gear, too. For example, one of my most recent REGENERODYNE receivers has a dial mechanism that was built for me by a close friend using parts from a FAX machine. OH YES, my friend Julio had to do this for me, as yours truly mechanical engineering abilities are approaching almost ZERO! So, follow Arnie Coro's advice and look around for old FAX machines at garage sales, closets, attics and maybe your workplace... those old1980's generation of FAX machines are a treasure chest of electronic and mechanical parts waiting to be recycled amigos!
This is the mid-week edition of Dxers Unlimited, amigos... you can subscribe to our e-mail distribution list by sending an e-mail message to MAJORDOMO@RHC.CU and then leave the subject line blank... In the body of the message typesubscribe dxers_l, that is subscribe delta x-ray echo romeo sierra, underscore lima... dxers the little line below the line, that's the underscore, and then the letter l like in lima... Majordomo software will confirm the subscription and then start sending twice weekly the scripts of the show for you to read, and these scripts do include GRAPHICS.... that then you can store in your hard drive for future reference.
Now, the popular YOU HAVE QUESTIONS section of Dxers Unlimited... Today's question sent by a listener in the Netherlands:
Arnie, here in Europe the vacuum tubes that are available have European type designations. Some of your circuit diagrams show North American tube type designations.... What can be done about that?I do want to build the basic REGENERODYNE short wave receiver, using the European tube types.....
ANSWER: Well my friend from Holland, you are right, and it was not a mistake but maybe a shortsightness, as I should have included the European equivalents of the vacuum tubes used... Don't worry, I will do it from now on -- every time that a vacuum tube nostalgia circuit is made available here, I will include the tube type designators for North American, European and Russian tubes! And in a direct to you e-mail reply, I already sent the equivalents of the tubes used in the REGENERODYNE basic circuit.... a design originally provided by Gary Johanson, a GLOW BUGS enthusiast!!!
And now, as always at the end of the show, here is Arnie Coro's Dxers Unlimited's HF plus 6 meters propagation udpate and forecast:
Solar activity is MODERATE, and we may see yet another big solar flare during the next 48 hours. In our weekend edition for August 25 at the Dxers Unlimited website, you can see several photos of the Sun and its prominent region 9591 that still is keeping its delta magnetic configuration...
Expect possible geomagnetic disturbances during the next 3 to 5 days, and if yet another big flare happens, then you will perhaps witness the so called MOSS DILLINGER effect, or total radio blackout, due to the radiation storm caused by the big solar flares if the region that generates them is in a geoeffective position.
As solar flux is now approaching almost 200 units, and we are moving away from the summer, expect possible 15,12 and 10 meter openings, something that will be most welcome especially by those like yours truly who enjoy so much 10 meter band openings!!! Remember to send your radio hobby-related questions, signal reports and comments to arnie@radiohc.org, and Via AIRMAIL to Arnie Coro, Dxers Unlimited, Radio Havana Cuba, Havana, Cuba.
Prepared 28-Aug-2001; received by NY Transfer 29-Aug-2001, 16:00 EDT
Arnie Coro CO2KK
Havana, Cuba
Aug 28, 2001Postal address:
Arnie Coro, "Dxers Unlimited"
Radio Havana Cuba, Havana, CUBA
e-mail: arnie@radiohc.org
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