Radio Havana Cuba

Dxers Unlimited

Dxers Unlimited’s weekend edition for 27-28 October 2007

By Arnie Coro Radio amateur CO2KK Hi amigos radioaficionados around the world and in space… welcome to the weekend edition of Dxers Unlimited, RHC’s twice weekly radio hobby program. I am Arnie Coro, radio amateur CO2KK, now ready to share with you about seventeen or maybe eighteen minutes of on the air and on the world wide web time. By the way, we are on the WEB streaming audio from

three: Our technical topics section is now on the air with information about a rather unsual radio frequency detector circuit using light emitting diodes of different colors, that require the use of very high local oscillator injection voltages , something that gives this circuits a unique property of handling very strong signals. Green light emitting diodes as well as blue ones have already been tested at my workshop under experimental conditions, feeding a seven megaHertz signal from a very nice signal generator… and Saturday I will be testing another broadband double balanced mixer using white-blue light emitting diodes that require between 3.2 and 3.8 volts to operate. The product detector circuit is followed by a high gain low noise audio amplifier, that has a variable gain setting with a range between 50 and 100 dB… When the light emitting diodes product detector is connected to a radio frequency tuned circuit , and that circuit is coupled to an antenna, we have a very special direct conversion receiver with a unique feature of handling very high input signals without overloading… Item four: Coming up after a short break, is our most popular section of the program, ASK ARNIE, answering your questions on the air and also directly to your e-mail address… Standby for a few seconds amigos… ……… This is Radio Havana Cuba, the name of the show is Dxers Unlimited and here is item three ; ASK ARNIE, answering a radio hobby related question sent by listener Carlos from Mexico City, one of the worlds most populated cities… Carlos asks what he can do to reduce the extremely high noise level he is picking up with his two radios, on frequencies from 100 kiloHertz all the way up to around 25 megaHertz. He adds that above 25 megaHertz the noise level goes down on both radios, the small portable and the tabletop digital dial receiver. Carlos has tried several antennas and he tells me that so far he hasn’t been able to listen to weak stations on the international short wave bands… and I quote from his e-mail " Arnie, only the most powerful broadcast stations are able to go over the very high noise level… the weak ones simply can’t be heard. Well amigo Carlos, you may want to try a unique antenna that I have tested here under high noise level conditions with excellent results… It is also not too difficult to homebrew, and can even null the most powerful noise sources by turning it around. This type of antenna is known as a magnetic loop, and is nothing more than a big one or two turn coil tuned by a variable capacitor, to which another smaller loop is coupled. The circuit diagram of this type of antenna can be represented as a standard parallel tuned circuit with a link coupling to your radio. A typical receive only MAGNETIC LOOP can be built in a few hours, and you can use it indoors… right next to your radio receivers, because this type of antenna requires constant tuning when you change the operating frequency of the receiver by just a few kiloHertz. The antenna is typically used right next to your receiver, because as I already explained, you must constantly retune the variable capacitor to peak the antenna’s very sharp resonance … at the lower end of the tuning range of this one meter per side square antenna using a 300 picofarads maximum capacity variable capacitor the tuning is so sharp that just tuning your radio maybe ten kiloHertz up or down from the previous frequency will reduce the signal level by twenty or even thirty decibels…So, as you can imagine, using this antenna amigo Carlos is not very comfortable, because you must retune it constantly, BUT, for people having to deal with extremely high noise levels as is your case , the Tuned Magnetic Loop antenna is according to my experience practically the only alternative that you can put to work .

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Yes amigos, solar minimum is very much with us at this moment… many, many days without a single sunspot… many, many days of a blank Sun with the microwave solar flux measurements reaching bottom low figures that were not seen by scientists in many years, and as a matter of fact some solar researchers now believe that something is really changing 93 million miles away from Earth… as solar cycle 23’s minimum has already reached rock bottom low levels with the average number of sunspots going down to around 5… yes, you heard it right ZERO FIVE , and that is half the number of sunspots registered during the minimum of previous solar cycle 22 during 1996… This solar minimum may open up the question of the possible beginning of yet another Maunder Minimum ; that’s the name given to a long period of extremely low solar activity that happened between the years 1645 and 1715, a period of a bit more than 70 years , or the duration of roughly six consecutive solar cycles that have an average duration of 11.1 years. Astronomer Edward W. Maunder born in 1851 and who died in 1928,was the discoverer of that extended period of extremely low solar activity when he analyzed the records of solar optical observations .

Maunder found out that during one 30 year long period within the a bit more than 70 years of very low activity, solar astronomers were able to count only about 50 sunspots , while the normal count for three typical consecutive solar cycles is within the range of forty to fifty thousand sunspots… a one thousand to one ratio ….One outstanding characteristic of the Maunder Minimum was that The sunspot activity was then concentrated in the southern hemisphere of the Sun, except for the last cycle when the sunspots appeared in the northern hemisphere too.

According to Spörer's law, at the start of a cycle spots appear at ever lower latitudes, until they average at about lat. 15° at solar maximum.

The average then continues to drift lower to about 7° and after that, while spots of the old cycle fade, new cycle spots start appearing again at high latitudes.

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Si amigos, we do QSL, we do verify reception reports, and send a nice , beautiful QSL card upon receiving your detailed reception reports that should include the date, time, frequency and some details of program contents. Send your signal reports to arnie@rhc.cu or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba And now my friends, here is Arnie Coro’s Dxers Unlimited’s propagation update and forecast… Expect more days of zero sunspots Zero, zero, zero sunspots for almost 20 days in a row now. A single small sunspot appeared briefly October 6-7, then no sunspots for four days prior, one sunspot for the final few days of September, and none for the three whole weeks prior to that.

Until recently, solar scientists were believing that the solar cycle minimum had occurredin March of this year, something that the present period of zero sunspots has proven to be wrong. With such a long period of so few sunspots, at the beginning of November we might see a much lower 3-month average. This is because the sum of all the daily sunspot numbers from August 1 until now is only 492, and if we still see no sunspots through next Wednesday, when November begins, that total divided by the number of days for August-September-October (92) is only 5.4.a much lower figure than the September of 1996 minimum of 8.7 sunspots… Hope to have you all listening to our show’s midweek edition next Tuesday and Wednesday UTC days amigos !!! Send your signal reports and comments to arnie@rhc.cu or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana , Cuba

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