Dxers Unlimited mid week edition for Tuesday 13 November 2018

By Arnie Coro
radio amateur CO2KK

Hi amigos radio aficionados around the world,  I am your host Arnie Coro and here is item one of today’s Dxers Unlimited….

three years ago , when daily solar flux figures were hovering around 100 units… looking at the northern skies, those of you living at higher latitudes were able to watch the aurora borealis displays caused by higher solar activity. But there is now a very small probability of more aurora borealis displays  soon … So forget about us picking up the watery sounding VHF signals bouncing back from the highly ionized auroral curtain that makes possible interesting 6 and 2 meters amateur radio contacts…

Much higher solar flux and more sunspots are required to improve the short wave propagation conditions. For those of us living closer to the equator aurora borealis is an almost never seen phenomenon… but I do recall during a solar cycle peak  a huge solar storm way back in 1989, when our Cuban weather guru Professor Jose Maria Rubiera described the red looking sky to the North as a very low latitude aurora borealis event…

Almost 20 years later the present Solar cycle 24 continues in the doldrums… with the daily solar flux levels not passing much higher than 70 … But, despite the very low solar activity , from time to time we do see those coronal mass ejections that send streams of charged particles to the space sorrounding the Sun…

Item two:  A lot of fun, yes a lot of fun is what you have when a just completed homebrew radio project is first connected to the power supply and the antenna… AND… It happens to work properly, but it is needless to say that not every time things come out as they should, and that was exactly what happened to me Sunday afternoon when trying to test for the first time a minimum parts count cascode direct conversion receiver project intended for our radio club’s newcomers …

After carefully checking the power supply polarity, and double checking that as I always do, the battery or power supply reversal polarity protection diode had been included into the circuit board… I proceeded to connect the antenna, and NADA… nothing happened… just a background hiss from the audio amplifier …

A careful check with a magnifying glass revealed  the cause of the malfunction… it was my fault…. The cause of the problem was a solder blob that was bridging two connections…. After disconnecting the power supply and picking up the excess solder with a nice wick made from the braid of an audio screened cable ,  I reconnected the circuit board to the power unit and the antenna…. and here is what can best be described as a very special feeling…

The receiver started immediately  to pick up stations around six megaHertz. Checking the three NPN transistors VFO frequency,  I read on the digital display of the frequency meter 6115 kiloHertz. Moving the variable capacitor slightly up brought the frequency to 6060 kiloHertz where Radio Havana Cuba woould be on the air in Spanish a few hours later…

A quick small color dot marked the dial , and then tuning slowing down I came across exactly 6000 kiloHertz. By the way in order to pick up the AM signals with the simple direct conversion receiver you must  exactly zero beat the carrier of the station — something that will produce just audio from the station and no beat note from the carrier frequency.

But, this receiver was designed as part of our amateur radio license training program, so I had to retune the variable frequency oscillator to exactly 7000 kiloHertz… and then playing with the coil and capacitor combination of the VFO to make it span from 7000 to 7200 kiloHertz..

That it is the radio frequency spectrum assigned worldwide for the exclusive use of the amateur radio service. By using a dual tuned bandpass input filter and a resistive pad radio frequency signal attenuator, this very simple radio immediately produced amazing results early Tuesday morning local time , when at around five thirty AM , just before sunrise , I started to pick up several Japanese radio amateur stations operating on CW very near the band edge of the 40 meters band…

Yes amigos, this circuit is a minimum  parts count direct conversion radio that when it was connected to my dipole  antenna using the antenna tuner, brought DX stations from Asia with signals that were very easy to copy…

This is yet another clear demonstration that you do not  need to spend a lot of money to really enjoy ham radio and have a lot of fun … By the way the circuit diagram is available by sending an e’mail to inforhc at enet dot cu… it is a small dot jpg file….

This is Radio Havana Cuba, the name of the show is Dxers Unlimited … I am your host Arnie Coro , radio amateur CO2KK and here is item three of this middle of the week edition of the program….

More about simple radio circuits that can be built at home, using common tools, after you learn such basics as identifying  and testing electronic components, reading circuit diagrams and properly soldering parts to circuit boards… Add to those abilities, a little later, how to design printed circuit boards, and yes,  I do expect that you buy yourself a good high quality digital multimeter and also as good as possible thermostatically controlled soldering station…. and really learn how to use it properly.

You can even go ahead and build some of the basic test instruments without having to wait for having enough funds in order to buy two or three more test instruments….  Kitchen table assembly of some simple radios is perfectly possible, but I warn you to really avoid damaging the kitchen table counter surface by burning it by misplacing the soldering iron !!!

Your best option is to prepare a medium size table, maybe a fold over one, and have it available , for example in  the attic, cellar or garage of your house !!! My two working tables, one for electronics and the other one for mechanical work are located in the garage, and one of them can be easily folded to the wall…

Now let me tell you more about home brewing some other simple circuits… One of my favorites is a very reliable , always easy starting quartz crystal oscillator…. It is an excellent test instrument , acting as a reliable signal source.

It uses two common NPN silicon transistors , and you can make quartz crystals , even slugglish ones , start generating radio frequency within the frequency range of 1 to 20 megaHertz… This two transistors simple circuit uses no critical parts, and will serve also as a frequency marker / calibrator… I am the happy owner of a quartz crystal that is marked as operating on exactly 7000 kiloHertz, and yes … it does oscillate very, really very near to that frequency, making it a very useful frequency marker.. right at the band edge of 40 meters and the harmonics fall very near 14, 21 and 28 megaHertz.

And talking about 40 meters, if the solar cycle continues to keep its activity at the present  very low levels, the amateur radio operators all around the world must realize that their chances for working nice DX above the 20 meters or 14 megaHertz band will be much diminished, making the installation of 160, 80, 40 and 30 meters bands antenna systems a really top priority…

The only other options left to enjoy ham radio if the present and the upcoming solar cycles are as poor as it looks like they are going to be are EME or Earth Moon Earth communications , and using the presently available low earth orbit satellites…. while we wait for the first ever amateur radio geostationary satellite in orbit above the equator….

Last but not least, prepare your station to use the popular digital communications modes, including ultra simple PSK31, the bare bones exchanges available with FT8, and learn how to use and promote the use of Olivia my favorite digital communications mode. EME contacts and ham satellites require installing special antennas, and in the case of EME, high power VHF, UHF or Microwave transmitters and extremely sensitive receivers…

Ham satellites at present are in my humble opinion not a very attractive option for the average amateur because the time windows available to work via satellite are not too frequent during the day and last for just barely a few minutes..

And now , at the end of the show… the consistently dissapoining bad news about the higher HF bands propagation… with the solar flux just barely near 70, and just a very weak sunspot active region with low magnetic activity, propagation on the 15, 12 and 10 meters bands is going to be poor… with only slightly chances of brief north to south and south to north openings… Best night time reception for short wave listening will be between 6 PM and 10 PM local time, on the frequency bands between 3  and 12 megahertz.

Send your signal reports and comments about this program to inforhc at enet dot cu or VIA AIR MAIL to Arnie Coro Radio Havana Cuba, Havana, Cuba

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