Dxers Unlimited's weekend edition 24-25 October 2009

Radio Havana Cuba

Dxers Unlimited

Dxers Unlimited's mid week edition for 24-25 October 2009

By Arnie Coro

radio amateur CO2KK

Hi amigos radioaficionados around the world ... welcome to the mid week edition of your favorite listener oriented and technically minded radio hobby program. Dxers Unlimited with yours truly Arnie Coro, radio amateur CO2KK at the microphone.

Here is now item one: Tropical band Dxing equinoctial season just coming to an end now, certainly helped by the very low solar activity that reduces ionospheric absorption to minimum values... I have picked up several Tropical band stations fromCentral America, and even from two African stations that were coming in just as the Sun was rising over the West coast of Africa , so the signals were traveling along the gray line propagation enhancement.

Once again , short wave receivers around the world are on and as alwyas lots of people are picking up the local news broadcasts from such far away nations as New Zealand, South Africa and Japan.

Item 2 : My new two half wave in phase 40 meters band antenna is working very well , despite the fact that due to the lack of space it could not be installed in a totally horizontal configuration. As a matter of fact the antenna has one rather short horizontal section, and two sloping ends, that makes it a rather odd looking dipole.

Anyway, it matches very well on 80 meters , where it is just a half wave dipole, and on 40 meters the two half waves in phase are providing excellent service, both at high take off angles, and it seems like the two slant wires at the ends have some kind of directional effect, as signals from Japan are coming in every early morning on 40 meters...

One of the legs of the antenna is sloping towards Japan, and this is why I believe that there is some sort of enhancement in that direction.

The antenna is fed with twin 75 ohms downlead, but it will soon be replaced with a 400 ohms open wire line now in the process of been built.

The 75 ohms twinlead has much higher losses on 40 meters because of the impedance mismatch, but on 80 meters it acts as a rather low loss feeder.

I also tested this antenna on the 20 meters band , getting the CO2KK ready to operate during this weekend CQ Worldwide ham radio contest.

Si amigos, yes my friends, it you don't have enough room to install a low frequency bands antenna horizontally, don't hesitate to try sloping the ends and use open wire feeders, a balanced low loss transmission line, you will be amazed how well this antenna configuration works and let me add that it does not use any type of loading, so its efficiency is higher than what can be achieved with antennas that use loading coils and capacity end load devices.

More radio hobby related information, coming to you from Havana, in just a few seconds !!!

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You are listening to Radio Havana Cuba, the name of the show is Dxers Unlimited, and here is item three of today's program amigos...

It's our technical topics section, that is winning more and more enthusiastic listeners acceptance every day...

Today I will be telling you about how to recycle somewhat newer, but cheap short wave radios that have a digital frequency readout, that can be in many cases carefully removed and re-used as the readout for your next homebrew radio project.

They are not super seven digits displays, the ones I have recycled have a five digit readout, that will give you a reading of up to one kiloHertz, which is more than enough for most homebrew projects.

While recycling those cheap short wave solid state receivers, you can try to recover other components too, like the small loudspeaker and the telescopic whip antenna, but I warn you that the high level of circuit integration makes recovering more parts for further use quite difficult if not impossible...

And now still at the technical topics section, but jumping back aboard the time machine, let me also tell you about a most recent experimental transmitter that I assembled together with a newcomer to amateur radio, that was able to upgrade to the class of license that allows operation on the short wave bands.

Here in Cuba we have a beginners license that authorizes the use of the two meters and the 160 meters bands, where you are supposed to operate for a two year period before taking the second class license test that allows operation on the HF bands and changes your callsign from CL to CM....

Well, my amigo needed to go on the air on 40 meters as soon as possible to make good use of his new CM callsign, and in just a few hours we assembled a nice little 6 Watts output crystal controlled CW transmitter that uses a single ECL86 type vacuum tube... the ECL86 has a triode and a pentode inside the same glass envelope and its a pretty powerful tube despite its small size.

The new transmitter uses the triode section as the crystal controlled oscillator and the pentode is the radio frequency power amplifier stage, that has a very well designed PI network output to match the antenna.

We also tested it with the lower power ECL82 similar vacuum tube and it delivered about 2 Watts of a very clean nice CW signal.

The little rig can be easily assembled and uses no rare or as some amateurs describe hard to find parts...unobtanium components... the final amplifier output network coil is wound on a 25 millimeters or one inch diameter length of PVC pipe and the two tuning capacitors came from junk AM broadcast band radios that had no collectors value at all.

The only problem is that the rig needs a hard to find locally quartz crystal , that must be resonant to a frequency at the low end of the 40 meters band... Anyway, this time we were luck
and I found a type FT243 type crystal that was made in 1944, and that came alive nicely after taking it apart, washing the quartz blank with a mild detergent, borrowing my wife Roxana hair dryer for a while, and re-assembling it...

The crystal oscillates on 7015 kiloHertz, which is a nice CW frequency for 40 meters band operation, and so far , using a simple voltage doubler power supply, we have even worked a station in Slovenia with the 6 Watt homebrew single vacuum tube rig...

The next project for my friends's station is going to be a Regenerodyne receiver, for which we have now finished collecting all the parts...

By the way NEVER, yes you heard it right, NEVER start homebrewing an electronic circuit without having all the parts required to build it in a box... and I always recommend to whenever possible to test each part , so that you can sure that it is OK.

One of the worst nightmares that a radio hobby fan may have to deal with, is when you solder a defective electronic componen into a new project...

It will take a lot of time to find out that a nice looking elecrolytic capacitor or a shining metal case transistor are bad...

Believe me, the time spent testing the parts before starting to assemble them is really worth every second that you dedicate to that task. ...

As you have just heard, getting on the air on 40 meters or for that matter also on 80 and 30 meters CW can be achieved quite easily , without having to locate rare or exotic components, and let me add amigos that the ECL86 vacuum tube is as rugged and reliable as you can think, so it will last for a long time in this particular application.

Some time ago we tried the same circuit design, but using two separate vacuum tubes, a 6C4 triode as the oscillator and a 6V6 tetrode amplifier. It works very well , and once again proved that ham radio need not be an expensive hobby at all.

I do admit that those homebrew rigs don't look as nice as the expensive factory built transceivers , but when heard on the air, no one can tell if you are sending that nice sounding CW with your almost zero cost breadboard assembled rig or with a sophisticated transceiver that may cost up to several thousand dollars !

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You are listening to Dxers Unlimited's weekend edition , coming to you from Havana... you can send your radio hobby related questions and comments about this and other Radio Havana Cuba programs by e-mail to inforhc at enet dot cu, again inforhc at enet dot cu... or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba...

Now here is the most popular section of Dxers Unlimited, YOU HAVE QUESTIONS, and Arnie tries to answer them...

I received several e-mail messages with feedback from our weekend edition's section that was devoted to antenna tuners... and it became quite clear to me that many short wave listeners , after assembling their first antenna tuner, become aware of how much even a very simple tuner helps to improve reception.

My favorite antenna tuner design is the PI network , because it offers a very wide tuning range, is easily built, and as a bonus provides extra filtering action at the input of your receiver.

For receive only or low power transmitting applications, a PI network antenna tuner is built using a homebrew coil wound on a white PVC plumber's pipe of between 19 and 25 millimeters diameter, that is from three quarters to one inch diameter.

Using common household number 18 or number PVC insulated wire will provide higher Q, because the insulation between turns acts to separate them a bit less than one wire diameter.

For the frequency range from 6 to 22 megaHertz, that covers all the international short wave broadcast bands and everything in between including the most popular amateur radio bands, your antenna tuner coil will require between 20 and 30 turns...

You will need to use two air spaced variable capacitors with maximum capacity between 200 and 400 picofarads, and they may be of the so called receiving type capacitors, because you don't need high insulation between the fixed and moving plates of your variable air spaced capacitor.

Wind your coil and make a mark every five turns , then unwind the coil and very carefully remove the insulation for a very short length at every mark that you made... Next step is to solder a length of the same wire to each of the uninsulated areas...

You may then just cut the new wire at about 2 centimeters and remove the insulation... This will give you a coil with several taps, that can be selected by means of a cocodrile clip !!!

Install the two capacitors and solder a short length of thin diameter coaxial cable to the tuner....so that it can be connected to your radio receiver...

The center conductor of the coax goes to the coil and the fixed plates of the capacitor at the end of the tuner , and the shield or braid is soldered to the air spaced capacitors rotor plates or ground connection...

You will also need to connect the two capacitor's ground lugs together with a short length of coaxial cable braid...

The input of the tuner is connected to your antenna and ground system, and all that is left for you to do is start experimenting by selecting a number of turns of the coil and moving the two capacitor's variable plates while listening to a station...

Soon you will find out how much the antenna tuner improves your reception, not only by peaking the antenna system but also because of the significantly enhanced selectivity...

And now at the end of the program, here is the HF plus low band VHF propagation update and forecastt...

Solar flux at once again at around 70 units, and we are returning to an all quiet conditions after a little bump from a stream of solar protons... The very small sunspot that appeared during the middle of the week vanished... but a last minute report tells us about a new active sunspot region that soon may be receiving its numerical designator... So for ham radio operators that will be participating in the CQ WorldWide DX Contest, here is Arnie Coro's CO2KK advice... closely monitor the 15 and 10 meter bands for possible very short openings that will make possible nice DX contacts to take place, as many operators around the world will be on the air during the 48hours contest period...nts

Hope to have you listening to the program's midweekedition amigos, and don't forget to send your signal reports and comments to inforhc at enet dot cu or VIA AIR MAIL to Arnie Coro , Radio Havana Cuba, Havana, Cuba

Dxers Unlimited's mid week edition 6-7 Oct 2009

Radio Havana Cuba

Dxers Unlimited's mid week edition for 6-7 October 2009

By Arnie Coro

Radio Amateur CO2KK



Hi amigos radioaficionados listening to this program anywhere in the world... Your radio receiver is now tuned to Radio Havana Cuba's Dxers Unlimited's mid week edition coming to you from sunny Havana,the capital city of Cuba, where on Monday we had a record breaking temperature of 35.6 Centigrade at one PM local time...

Summer , yes, summer weather well into the autumn season, and correspondingly we had our share of thunderstorms due to the daytime heating up of the lower atmosphere... So far no tropical storms or hurricanes forming near to us, and this has been so far an extremely quiet Atlantic, Caribbean and Gulf of Mexico hurricane season.

But, Cuban radio amateurs continue to do their regular emergency drills to keep their ham radio stations ready to be deployed in case a storm develops later in the season. Here in Havana we had an emergency drill on Sunday, with stations using several different bands and communications modes. It was described by the organizers as a very succesful event, that helped to bring new radio amateurs into the emergency communications nets that are organized at each of the Cuban capital fifteen municipalities.

Every year members of the Cuban Federation of Radio Amateurs participate in our national emergency nets that are capable of providing communications links even under the most difficult circumstances, something that is very much appreciated by the Cuba Civil Defense System .

I am Arnie Coro,radio amateur CO2KK,your friend in Havana, and here is our next news item of today's program.... Zero sunspots once again, for three consecutive days, and now one more... no sunspots and the solar flux again at very low levels, below the 70 units mark... with more than 200 days of this year 2009 registered as absolutely spotless, radio amateurs and short wave listeners hope that soon solar cycle 24 will start producing sunspots on a regular basis .

Those who were worried about a possible new Maunder Minimum, are now feeling a lot better after at least three sunspot groups appeard on the solar disc, they did surely caught solar researchers by surprise, because the new sunspots caught everyone by surprise. There is no doubt about the fact that all three active regions, however small and short lived, did belong to the new solar cycle 24.!

Once again, asking for the opinions of several well known solar scientists, I found out that they all agree that the magnetic fields that generate sunspots just have proven to be extremely weak, as a a matter of fact they are showing a trend to become weaker and weaker during the past several year, as documented by several research papers that were published recently.!

As regular Dxers Unlimited's listeners will surely remember, the last continuos stretch of spotless days lasting for 51 days in a row, came just one day short of what happened during the summer of 2008, when cycle 23's record of 52 days without sunspots happened.

I'll be back with more radio hobby related information in just a few seconds I am Arnie Coro , radio amateur CO2KK in Havana.


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This is Radio Havana Cuba, the name of the program is Dxers Unlimited, and here is our next item:
Early morning, pre-sunrise propagation conditions on the lower frequency bands, from 500 kiloHertz up to about 8 megaHertz continue to be rather good, providing us with some nice opportunities to pick up DX stations..., especially those located along the darkness path to the West and Northwest of where you are located.

Here in Cuba, it is quite evident at our Havana's Tropical latitude of 23 degrees North, that weather systems still belong to the summer season, so the high static noise levels generated by thunderstorms are still making reception of low frequency signals rather difficult., because they do spoil the signal to noise ratio significantly.

But , as said earlier, in a recent Dxers Unlimited program, just before sunrise local time, the QRN generated by the atmospheric noise level goes down, because the number of thunderstorms at that time of the day is lower than at any other period.

Again, be aware that Pre-sunrise propagation conditions also provide much better propagation to the West and Northwest of your location, a fact that must be taken into account .

Although North-South and South-North propagation paths do open up also during the pre-sunrise period, it is quite clear that signals coming from due West or from the North West are several dBs better .

As we enter more and more into the autumn equinoctial DX season, propagation conditions on frequencies between 500 kiloHertz and eight megaHertz will improve , making possible for radio amateurs to enjoy a short period of much better DX possibilities, that will be coming to an end when the transition to winter season propagation takes place at the end of this month !!!

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Homebrewing crystal sets, radios that don't use any device to amplify the received signals is a lot of fun, and also very instructive for the newer generations. But, in order to provide good headphone volume, those radios do need two basic elements : First of all , you MUST use high impedance headphones for that extra sensitivity required , and second, don't attempt to make your demostration crystal set a piece of miniature art.

Everytime someone visits my shack and takes a look at the two big coils of my prototype crystal set, they ask why are those two coils so big, and the answer is that they provide not only maximum Q factor, required to be able to separate between AM broadcast band stations, but that also provide maximum sensitivity of the one single diode passive device crystal set.

The two coils are wound using two inches or 50 millimeter diameter sections of PVC pipe. I use number 18 or 1 millimeter diameter enamel wire , and the winding requires 100 turns , close wound, with taps every 10 turns.

Each of the two coils is tuned independently using air space 365 picofarads variable capacitors, and they are top coupled by means of another variable capacitor that has a range from 10 picofarads to one hundred picofarads...

Another very important element to be considered is the selection of the best possible germanium crystal diode... something that can be done with the help of a digital multimeter... The germanium diode with the lowest breakdown voltage will provide the maximum sensitivity.

Using an external antenna and a ground connection, my high performance crystal set picks up stations as far as three hundred miles away during the local daytime hours, and at night I have been able to pick up stations from several Latin American countries, like Mexico,Colombia and Venezuela.

There are many crystal radio enthusiasts around the world, and building and operating those sets that use no external power source or amplifying devices is one of the more than 84 ways that you and I can enjoy our wonderful hobby !!!

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This is Radio Havana Cuba , the name of the show is Dxers Unlimited, and here is our next radio hobby related item... How even with a very simple , easy to homebrew amateur radio transceiver operating on the 40 meters ham band with a low gain antenna, it is possible to work DX stations half way around the world, under the worst ever propagation conditions seen amateur radio operators since the very early days of radio more than a century ago.


At the request of many listeners of the show, I am continuing to work on a e-booklet, in dot pdf file format, that will contain all the available information about the Super Islander, explaining among other things, why , after doing many 40 meters band propagation experiments , we found out that a power output of about 25 Watts was the minimum required to assure a good probability of making two way contacts with this equipment.


Yes, you can enjoy QRP or low power operation , by cranking down the power of the rig to 5 Watts or less, but if you need to assure a reliable two way contact during an emergency, the 25 Watts rig will increase the probabilities of communicating, something that will not happen running your rig at the 5 Watts power level.


As many of you familiar with the Islander and Super Islander design features, the transmitter module of the Super Islander transceiver is capable of sending both CW Morse Code radiotelegraphy signals as well as double sideband suppressed carrier voice signals. Using the CW mode of the Super Islander during our local evenings , it is possible to contact stations in Europe and Africa, and sometimes even as far as the Middle East.

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Amigos you are listening to the mid week edition of Dxers Unlimited, and here is now, once again, a quick reminder for long time listeners and also good news for those of you that are enjoying this program for the first time....

Yes, we here at Radio Havana Cuba do QSL, we verify your correct reception reports with a nice QSL card, and your comments about this and other Radio Havana Cuba programs are most welcome... Send your radio hobby related questions , that will be answered direct via e-mail and also on the air . Send mail to inforhc at enet dot cu, or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba.

And now , as always,when I am here in Havana and can compile all the required information ... here is at the end of the program Arnie Coro's exclusive Dxers Unlimited's HF plus low band VHF propagation update and forecasts.

Solar activity at rock bottom levels, solar flux at 69 units, and there are no active sunspot regions in sight... The daily sunspot number is zero.

Again ,once again an update, we are the enhanced autumn equinox propagation conditions, with their nice enhacement of AM medium wave broadcast band Dxing, reports that are reaching me from Dxers Unlimited's listeners around the world confirm that during the first few days of October , propagation conditions have gone down due to the lack of sunpsots and the very low solar flux , especially on the 40 , 30 and 20 meters amateur bands, and the 25, 22 and 19 meters international shortwave broadcast bands,the effects of the very quiet Sun are quite noticeable, with the bands in rather poor shape at this moment...

Hope to have you all listening to the weekend edition of Dxers Unlimited that will be on the air and on the WEB next Saturday and Sunday UTC days, amigos, and don't forget to send me your comments about today's program to inforhc at enet dot cu or VIA AIR MAIL to Arnie Coro, Radio Habana Cuba, Havana , Cuba...

They sure help me to make the next edition of Dxers Unlimited better for you all !!!

Dxers Unlimited's mid week edition 8-9 September 2009

Radio Havana Cuba
Dxers Unlimited's mid week edition for 8-9 September 2009
By Arnie Coro
Radio Amateur CO2KK

Hi amigos radioaficionados all around the world... Your radio is now tuned to Radio Havana Cuba's Dxers Unlimited's mid week edition coming to you from sunny Havana,the capital city of Cuba, where its more than 850 radio amateur are well prepared to deal with the second half of this year's tropical hurricane season.

The members of the Cuban Federation of Radio Amateurs participate in our national emergency nets that are capable of providing communications links even under the most difficult circumstances, something that is very much appreciated by the Cuba Civil Defense System.

By the way this is going to be one or main topics to be discussed at our Seventh National Convention that will take place in Camaguey city, with the participation of more than 250 Cuban radio amateurs and about 50 guests from government agencies and the Civil Defense national command.

I am Arnie Coro,radio amateur CO2KK,your friend in Havana, and here is our next news item of today's program.... Zero sunspots once again, with 200 days of this year 2009 registered as absolutely spotless, something that is having a very bad impact on high frequency short wave bands propagation conditions.

This sounds like we may be heading for another Maunder Minimum, and it has surely caught solar researchers by surprise, because they didn't expect that solar cycle 23 would last so long !!!

According to the opinions of several well known solar scientists, magnetic fields that generate sunspots just have proven to be extremely weak, as a a matter of fact they are showing a trend to become weaker and weaker during the past several years !!!

The last long stretch of spotless days came just one day short of what happened during the summer of 2008, when cycle 23's record of 52 days without sunspots happened.

Again, the total number of days of this year 2009 without a single sunspot seen has now added up to two hundred, equaling seventy nine percent 2009 that have gone by without sunspots.

I'll be back with more radio hobby related information in just a few seconds I am Arnie Coro , radio amateur CO2KK in Havana.


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This is Radio Havana Cuba, the name of the program is Dxers Unlimited, and here is our next item:

Early morning, pre-sunrise propagation conditions on the lower frequency bands continue to provide unique opportunities to pick up DX stations...

The AM medium wave broadcast band is going through a period when the QRN, the QR Nancy or radio noise levels are much lower than during the rest of the day...

It is quite evident here at our tropical latitude of 23 degrees North, that weather systems still belong to the summer season, so the high noise levels generated by static crashes from thunderstorms are still making reception of low frequency signals rather difficult.

But , as said earlier, just before sunrise local time, the QRN generated by the atmospheric noise level goes down, because the number of thunderstorms at that time of the day is lower than at any other period.

Pre-sunrise propagation conditions also provide much better propagation to the West and Northwest of your location, a fact that must be taken into account .

Although North-South and South-North propagation paths do open up also during the pre-sunrise period, it is quite clear that signals coming from due West or from the North West are several dB's better .

Monday evening I tried my new T type antenna on 160 meters, having to battle with big static crashes from not too distant thunderstorms, nevertheless I was able to make several nice two-way contacts using single side band voice , and one CW Morse code radiotelegraphy QSO.

As we enter more and more into the autumn equinoctial DX season, propagation conditions on frequencies between 500 kiloHertz and eight megaHertz will improve , making possible for radio amateurs to enjoy a short period of much better DX possibilities !!!

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At the request of several listeners , I am going to give a short glance at the ultra weak signal digital mode, that is known by its acronym ... WSPR, but that amateur radio operators using it are renaming as WHISPER.

Again this is a digital radio communications program that ranks as one of the most remarkable contributions to amateur radio software in recent times.... it is certainly a nice interesting example of how well written computer code is able to optimize the use of computers processing power in order to boost the reception of extremely weak signals. WHISPER , or WSPR is another good example of the ULTRA NARROWBAND digital modes that are opening a totally different scenario to weak signal communications.

I am talking here about the very small bandwidth digital modes, that use just a few cycles of radio frequency spectrum WSPR, the WHISPER, makes possible to operate with very low transmitter power output and still obtain good results !!!

Although the most popular and most used today easy to learn digital communications mode preferred by hams worldwide is PSK31, this keyboard to keyboard mode can be used even with older computers,.PSK31is also pretty easy to set up, and one can become quite familiar with the PSK31 mode operating procedures in just a few hours.

Now amigos, here is now our next radio hobby related item for your enjoyment.

Homebrewing of simple easy to build solid state radio receivers is a very rewarding experience ....

Yes amigos. Even the most simple radio, built around a tuned circuit, plus a crystal diode and a one transistor audio amplifier can provide excellent performance when properly designed and built.

Just recently I tried out an AM broadcast band receiver circuit that uses a minimum of electronic components, while still providing excellent selectivity , that is the ability of the radio to separate between stations.

The secret of this very simple receiver lies in the use of a very well designed input tuned circuit... It uses a large diameter , high Q coil and an air spaced 365 picoFarads variable capacitor. The high Q coil is coupled to a second matching coil that is designed to optimize the match between the antenna and the radio.

I wound the big coil on a three inch or 75 millimeters diameter length of PVC white pipe. The wire used is number 18 enamel insulated , and the coil has 70 turns, with taps from the bottom up every 10 turns.

By using a hand picked germanium crystal diode, the radio's sensitivity is much higher that what is normally achieved on this simple circuit when one uses any diode that is available without running into the trouble of measuring the diode's forward conduction voltage, in order to be able to select the one with the lowest value.

In order to provide the maximum possible amplification that can be achieved from the single stage audio amplifier, I measured the amplification provided by no less than fifteen transistors of the same type, and then using the one with the highest gain and lower internal noise.

This little radio was built as part of a training program at our Amateur Radio Academy that is made available to persons interested in becoming radio amateur operators.

The little radio uses a matching output transformer, so that the easy to find low impedance headphones can be used. This transformer matches the transistor's collector impedance to 16 ohms, so power transformer to the headphones is very good.

Parts count was intentionally kept to a minimum and the radio is battery powered . In actual practice it works quite well with just 3 volts DC coming from a pair of series connected AA type cells, but audio output is much higher when it is fed with 9 or 12 volts.

Tests using a 9 volts battery were very rewarding, as I was able to pick our own Radio Havana Cuba's six thousand one hundred and forty kiloHertz 49 meters band frequency using a wire antenna that is about 10 meters or a bit less than 35 feet long.

If you want to know more about this weekend project that can be assembled in just a couple of hours , just send an e-mail to inforch@enet.cu, again inforhc@enet.cu... or send a postcard or letter to Arnie Coro, Radio Havana Cuba, Havana, Cuba.
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You are listening to the mid week edition of Dxers Unlimited, and here is now, once again, a quick reminder for long time listeners and also good news for those of you that are enjoying this program for the first time....

Yes, we here at Radio Havana Cuba do QSL, we do verify your reception reports with a nice QSL card, and your comments about this and other Radio Havana Cuba programs are most welcome... Send your radio hobby related questions , that will be answered direct via e-mail and also on
the air .

Send mail to inforhc at enet dot cu, or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba.

And now amigos, as always,when I am here in Havana and can compile all the required information ... here is at the end of the program Arnie Coro's exclusive Dxers Unlimited's HF plus low band VHF propagation update and forecasts.

Solar activity at rock bottom levels, solar flux at 68 units, and there are no active sunspot regions in sight... The daily sunspot number is zero.

Again ,once again an update, we are already enjoying the enhanced autumn equinox propagation conditions, reports that are reaching me from Dxers Unlimited's listeners around the world confirm that since early September , propagation conditions have taken a turn for the better , especially on the 40 , 30 and 20 meters amateur bands, and the 25, 22 and 19 meters international shortwave broadcast bands...

Hope to have you all listening to the weekend edition of Dxers Unlimited that will be on the air and on the WEB next Saturday and Sunday UTC days, amigos, and don't forget to send me your comments about today's program to inforhc at enet dot cu or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana , Cuba...

They sure help me to make the next edition of Dxers Unlimited better for you all !!!

Dxers Unlimited's weekend edition 29-30 August 2009

Radio Havana Cuba
Dxers Unlimited's weekend edition for 29-30 August 2009
By Arnie Coro
Radio Amateur CO2KK


Hi amigos radioaficionados , happy to be reaching you anywhere you are enjoying our wonderful hobby! This is the weekend edition of your favorite radio hobby program,we are broadcasting from Havana,the two million two hundred thousand population capital city of Cuba...

I am Arnie Coro,radio amateur CO2KK,and here is now our first news item ....

Yes, it will sound quite routine to regular listeners and unfortunately it is .... , but really worth bringing it to you all in great detail because of it's impact on current short wave radio propagation conditions.

The Headline:
Forty nine, yes one day short of fifty, forty nine consecutive days without a single sunspot seen on the solar disc... Yes, you have heard it correctly... more than a month and a half without a single sunspot seen by the scientists that are keeping a constant watch active 24 hours a day.

The total number of days of this year 2009 without a single sunspot means that seventy nine percent of this year has gone by without a single sunspot. So, once again we are well into an extended new solar minimum that marks the third downward dip of solar cycle 23 !!!.

If we go to the year when solar cycle number 23 started its downward phase, the total number of spotless days recorded has passed the seven hundred mark a figure well above the typical solar minimum number of spotless days that is four hundred and eighty five days.

Again, today I will add yet another example of the impact on radio propagation that the present extended solar minimum has had... Here are some more practical results of this outstanding lack of solar activity that include a total lack of near vertical incidence skywave propagation on the 40 meters amateur band, that is happening because of the extremely density of the Earth's ionosphere .

The very thin E and F1 layers are uncapable of supporting the very useful NVIS or Near Vertical Incidence Skywave propagation mode

YES !!! This is Radio Havana Cuba, the name of the program that you are listening to right now is Dxers Unlimited:

Let's face it amigos !
We are having to deal with an extremely QUIET SUN:
According to sunspot counts, the longest stretch of spotless suns during the current solar minimum was 52 days in July, August and Sept. of 2008.

The current sequence of totally blank, spotless, suns is putting that record in jeopardy.

The sun is entering its 50th consecutive day with no sunspots, and there are none in the offing, so we are approaching the day that the current record of spotless days for this solar cycle is about to be broken !.

The Very Deep and lengthy new solar minimum continues. I must insist on the fact that we are now having to deal with an extremely weak ionosphere, with the free electron count per cubic centimeter at values that are very rarely seen during a typical solar minimum.

This weak ionosphere is uncapable of sending back to Earth radio signals above 20 megaHertz for most of the 24 hours of the day... So in actual practice any radio signals that are transmitted on frequencies higher than 20 megaHertz are automatically going out into space without practically any attenuation at all.

Stay tuned for more radio hobby related information amigos... I'll be back with you in a few seconds after a short break for station ID.

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This is Radio Havana Cuba , the name of the show is Dxers Unlimited, and here is our next radio hobby related item... How even with a very simple , easy to homebrew amateur radio transceiver operating on the 40 meters ham band with a low gain antenna, it is possible to work DX stations half way around the world, under the worst ever propagation conditions seen amateur radio operators since the very early days of radio more than a century ago.

At the request of many listeners of the show, I am working now on a e-booklet that will contain all the available information about the Super Islander, including the philosophy behind the design, explaining among other things, why , after doing many 40 meters band propagation experiments , we found out that a power output of about 25 Watts was the minimum required to assure a good probability of making two way contacts with this equipment.

Yes, you can enjoy QRP or low power operation , by cranking down the power of the rig to 5 Watts or less, but if you need to assure a reliable two way contact during an emergency, the 25 Watts rig will increase the probabilities of communicating, something that will not happen running your rig at the 5 Watts power level.

As many of you familiar with the Islander and Super Islander design feature, the transmitter module of the Super Islander transceiver is capable of sending both CW Morse Code radiotelegraphy signals as well as double sideband suppressed carrier voice signals. Using the CW mode of the Super Islander during our local evenings , it is possible to contact stations in Europe and Africa, and sometimes even as far as the Middle East.

Our experience shows that when propagation conditions are a bit above normal, later during the late evening, after about two o'clock in the morning local time here in Havana, stations from Australia, New Zealand and Japan start to come in, and one can contact them until shortly after sunrise.

I do admire the Japanese CW operators very clear sending, something that makes reception a lot easier than when one has to deal with operators that don't send the Morse Code characters with the proper spacing between them, as well as between words.

Yes amigos, 25 Watts output into a half wave dipole or a vertical quarter wave antenna , is all that is required during the peak propagation periods, when DX is coming in despite the extremely low solar activity. My perception is that the 40 meters band continues to be , the best all around compromise for ham radio operators that come back home from work after five PM local time .

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Si amigos, here is once again, the section of Dxers Unlimited that you have rated as the number one most popular of them all.... ASK ARNIE, answering your radio hobby related questions via e-mail directly and also on the air for the benefit of other listeners that may want also to learn about the same problem...

ASK ARNIE today will be answering a question sent by listener Alexander from Glasgow , Scotland , about a simple regenerative receiver circuit that he recently read about... It is known as the Kitchin Regenerative, honoring the name of the author of that design Charles Kitchin , an American radio amateur

Well amigo Alex, all I can say is that the Kitching solid state simple regenerative receiver works very well when properly built,it is relatively easy to homebrew and a delight to operate, because operating a regenerative receiver is certainly challenging !

I have built several of them here, as well as the also popular Paul Harden's Desert Rat regenerative using easily available electronic components. The latest Kitchin regenerative was actually built by my fourteen years old grandson, Arnie Coro the Fourth, who will soon be on the air from his own amateur radio station. Assembling the short wave regenerative receiver was a very rewarding experience for him, and he is delighted with the results achieved with a very short length of wire for an antenna.

I have tested both the Kitchin and the Desert Rat regenerative receivers on frequencies as high as 15 megaHertz , that is the 19 meters international short wave broadcast band that spans from 15.1 to 15.8 megaHertz. Both solid state regenerative receivers become difficult to tame about 18 megaHertz, something to be expected according to several articles I have read that deal with solid state versiona of regenerative receivers .....

And now amigos, as always at the end of the show, here is your friend Arnie Coro's Dxers Unlimited HF plus low band VHF propagation update and forecast.... Finally coming to an end... the sporadic E skip season is over now, yes, you won't be able to enjoy the sudden band openings on 10 or 6 meters, or the TV DX signals on the low band channels.

Solar activity continues at extremely low bottom levels with now almost 51 consecutive days without a single sunspot seen... so we are dealing with a very weak ionosphere, very low ionospheric absorption and as expected the daytime maximum useable frequency curve shows a very slow rise after daybreak, barely reaching 20 megaHertz at the best moments on the most favorable paths.

I hope to have you all listening to the mid week edition of Dxers Unlimited that will be coming to you next Tuesday and Wednesday UTC days amigos !!! AND, don't forget to send me your comments about this program to inforhc at enet dot cu, again inforhc at enet dot cu, or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba..

Dxers Unlimited's midweek edition for 25-26 August 2009

Radio Havana Cuba
Dxers Unlimited's mid week edition for 25-26 August 2009
By Arnie Coro
Radio Amateur CO2KK

Hi amigos radioaficionados all around the world...Yes, you are now listening to the mid week edition of your favorite radio hobby program,coming to you from sunny Havana,the capital city of Cuba, where radio amateurs continue to enjoy the excellent, just after local sunset ,propagation conditions...

Amigos I am Arnie Coro,radio amateur CO2KK,your friend in Havana, and once again here is our first news item of today's program.... It may sound as a repeat of a previous program, but it isn't...

Headline: Forty Five !!! YES !!! forty five consecutive days without a single sunspot seen on the solar disc...

Amazing, , surely surprising and intriguing for solar scientists, 45 days without sunspots as you have just heard...we are just one a week away from tying up this solar cycle's record of 52 days without sunspots, that happened during the summer of 2008.

Not a single sunspot seen by scientists for almost forty six days by the time you will be hearing this program... Let me add that heliophycisits , the solar scientists , are keeping the their watch active 24 hours a day. So far a month and a half without sunspots !!!

The total number of days of this year 2009 without a single sunspot seen has now added up to what equals to eighty percent of 2009 gone by without sunspots. So, once again, let me emphasize that we are well into an extended solar minimum., that has had so far three downward dips, with very small recovery periods in between.

Again, as I already said here recently, and to underscore the terrible impact on short wave propagation that the present extended solar minimum has had, here is still more information about the practical results of this outstanding lack of solar activity that include , that we have witnessed for the first time in many years the maximum useable frequency during our local evenings staying for hours at a time below the seven to eight megaHertz segment of the radio frequency spectrum!!!

This is Radio Havana Cuba, the name of the program is Dxers Unlimited, and here is our next item:

As stated in a recent edition of Dxers Unlimited, the digital communications modes have become more and more popular among the world's amateur radio operators, among other things, because those computer programs are able to provide two way links when voice and even CW Morse code radiotelegraphy simply don't work because of very poor short wave propagation. The narrowband digital modes have acted as a sort of “life saver” for daily ham radio activities on the HF bands.

Extremely small bandwidth digital modes make possible to operate with very low transmitter power output , something that in turn makes possible for amateur radio operators to use their HF stations from locations such as crowded apartment buildings and condominiums where electromagnetic compatibility, interfernce problems, rule out the use of standard short wave transceivers that run between 50 and 100 Watts to the antenna.

The most popular a and easy to learn how to use digital communications mode used by hams worldwide is known as PSK31, a keyboard to keyboard mode that can be used with older computers, as it doesn't require a powerful machine to operate properly. It is also pretty easy to set up, and one can become quite familiar with PSK31 operating in just a few hours, something that cannot be said of other more sophisticated digital modes.

Ideally I will recommend to you when setting up a PSK31 station to use a laptop or notebook computer, because those machines screens with their liquid crystal displays are less noisy than monitors using cathode ray tubes.

Now here is our next radio hobby related item for your enjoyment.
Daytime AM Broadcast Band Dxing
It can prove to be quite amazing. I am talking about pure ,so called surface wave propagation, that rules out any signals coming back to your radio reflected from the Earth's ionosphere.

It is true that it may be boring at times, as you pick up the same DX groundwave stations over and over again, but once in a while, you may be able to add a new one to your logbook.

For example, if you are familiar with the Norton Equation that clearly show how medium wave broadcast band signals propagate, it is quite clear that stations operating from the lower limit of the band, that is , from 530 kiloHertz up to around 730 kiloHertz , propagate via surface wave much better than stations operating on frequencies above the 730 to 750 kiloHertz segment.

For all practical purposes AM medium wave Dxers split the band into three areas. The above mentioned minimum surface wave attenuation part between 530 and 730 or 750 kiloHertz, followed by the segment from 750 kiloHertz up to 1200 kiloHertz or so... The tail end of the band, from 1200 to 1700 kiloHertz is where the highest signal attenuation of the surface wave happens.

Sometimes , AM stations go off the air for one reason or the other... they may experience a transmitter breakdown, or the AC power line may fail and the standby Diesel generator may not start up automatically, or in a worst case scenario, the antenna system may be badly damaged by weather related events, that include lightning as well as tornadores an hurricanes.

Whenever an AM station goes off the air , a “hole” opens up that will make possible picking up stations that are not heard at your location. Actually you may find that the stations that went off the air opens up more than one “hole” of DX opportunities, because it makes reception on adjacent channels a lot easier.

AM broadcast band surface wave Dxers are always dreaming of traveling to a very low noise area, right next to the sea, and installing several highly directional Beverage antennas .

A unique location for an AM Medium Wave Broadcast Band Dx Expedition

I have had the unique opportunity of enjoying superb surface wave propagation conditions when vacationing at Cuba's number one beach resort, Varadero.

At the extreme end of the Hicacos Peninsula in Matanzas province far away from the big hotels, the radio noise level is very low, especially during the winter months, making possible what can best be described as amazing DX pickups !!! .

Using several different antennas that include big tuneable loops and the already mentioned long wire resistor terminated Beverage antennas, I have been able to pick up AM broadcast stations many hundreds of miles away with outstandingly good signals.

Of course that such a DX expedition can only be organized once or maybe twice a year, but all I can say amigos, is that it is a really rewarding experience. If you decide to set up camp at the remote site, then you will be rewarded twice, because propagation conditions during the two hours before and after sunrise and sunset will also bring in lots of AM broadcast band stations.

During this extremely long period of very low solar activity, Dxing conditions on the AM broadcast band have been absolutely fantastic due to the very low ionospheric absorption that is typical of extended periods when the ionosphere's distribution of free electrons per cubic centimeter is at rock bottom levels.

Si amigos, yes my friends, oui mes amis... this extended solar minimum has brought up what could best be described as exceptional AM broadcast band Dxing conditions, and all the information available is pointing at the fact that the present very nice propagation on frequencies below two megaHertz will continue for at least one more year !!!

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You are listening to Radio Havana Cuba, this is the mid week edition of Dxers Unlimited, our radio hobby program that goes on the air twice weekly with the most up to date propagation updates and forecasts, always heard at the end of the program.

Now here is our next item radio hobby related item !...

For your enjoyment amigos, here is once again, ASK ARNIE, la numero uno, the most popular section of the show, answering your radio hobby related questions as soon as they come in to inforhc at enet dot cu , or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba.

Today's question has reached me from listeners in five countries you are enjoying very much the excellent low frequencies propagation conditions. They all are asking for advice on how to improve their antenna systems , in order to pick up more stations on frequencies between 400 kiloHertz and 2 megaHertz
Well, after reviewing my antenna files, I have sent them data on magnetic loops, Beverage antennas and the K9AY antenna system, that according to my own experimental results are the three best options for Dxers wanting to improve reception on the lower frequencies.

Once again amigos, here is your friend Arnie Coro's advice... start thinking about an autumn equinoctial season with very low solar activity that will continue right into the end of the year, and expect a winter DX season with extremely low maximum useable frequencies prevailing during the local daytime hours, so all your efforts improving the low frequency antenna systems are worth every minute devoted to them !!!.

As a good friend of mine said recently at a radio club meeting..Now is the right time for homebrewing and installing better antennas for the frequency range between 100 kiloHertz and 10 megaHertz, because that's the part of the radio spectrum where most of the activity is going to concentrate if sunspots , as expected, continue to be absent from the solar disc.

Don't forget that if you are a ham radio operator, and really want to work DX during this extended solar minimum be sure to add to your already highly efficient 20 meters band beam antenna, at least a long wire or an inverted L for the lower frequencies bands, and if you happen a lot of real estate available for installing antennas, don't overlook the possibility of setting up a large size wire dipole mounted at no less than 20 meters above the ground level !!!

Right at this moment, as we approach the autumn equinox, you will find that after local sunset, 30, 40 , 60 and 80 meters will be the best bands for DX during the hours of darkness, and those bands do require big antennas in order to be able to work distant stations at all !!

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Now a reminder for long time listeners and a bit of news for those of you that are enjoying this program for the first time
Si amigos, we at Radio Havana Cuba do QSL, we do verify your reception reports with a nice QSL card, and your comments about this and other Radio Havana Cuba programs are most welcome... Send also your radio hobby related questions , that will be answered direct via e-mail and also on the air . Send mail to inforhc at enet dot cu, or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba.

And now amigos, as always,when I am here in Havana and can compile all the required information ... here is at the end of the program Arnie Coro's exclusive Dxers Unlimited's HF plus low band VHF propagation update and forecasts.

Solar activity at rock bottom levels, forty five days without sunspots, and now a three new coronal holes may send high speed solar wind gusts to Earth within the next several days. Solar flux at just 66 to 67 units and ZERO SUNSPOTS !!!

Again for your information amigos, the upcoming autumn equinox propagation conditions are due to start around the first week of September, and hopefully we will see higher daytime maximum useable frequencies worldwide for a period lasting about six weeks , between the second week of September and the end of October.

Hope to have you all listening to the weekend edition of Dxers Unlimited next Saturday and Sunday UTC days, amigos, and don't forget to send me your comments about this edition of the program to inforhc at enet dot cu or VIA AIR MAIL to Arnie Coro, Radio Habana Cuba, Havana , Cuba...

They sure help me to make the next edition of Dxers Unlimited better for you all !!!

Dxers Unlimited's weekend edition 22-23 August 2009

Radio Havana Cuba
Dxers Unlimited's weekend edition for 22-23 August 2009
By Arnie Coro
Radio Amateur CO2KK


Hi amigos radioaficionados all around the world , anywhere you are enjoying our wonderful hobby! ..This is the weekend edition of your favorite radio hobby program,coming to you from Havana,the capital city of Cuba...I am Arnie Coro,radio amateur CO2KK,and here is our first news item of today's program....

It's a repetition of recent headlines, but really worth bringing it to you all

Headline: Forty threety one consecutive days without a single sunspot seen on the solar disc... Yes, you have heard it correctly... almost a month and a half without a single sunspot seen by the scientists keeping the solar patrol watch active 24 hours a day.

The total number of days of this year 2009 without a single sunspot seen has no increased to 184, that putting it in a somewhat more easy to undertand form means that seventy nine percent of this year has gone by without a single sunspot. So, once again we are well into an extended new solar minimum that marks the third downward dip of solar cycle 23 !!!.

If we go to the year when solar cycle number 23 started its downward phase, the total number of spotless days recorded has reached the amazing figure of six hundred and ninety five days, a figure well above the typical solar minimum number of spotless days that is four hundred and eighty five days.

Again, and to make you all aware of the terrible impact on short wave propagation that the present extended solar minimum has had, here are some more practical results of this outstanding lack of solar activity that include , outstanding daytime propagation on the AM medium wave broadcast band, that is happening because of the extremely low ionospheric absorption . The very thin D layer starts to disappear as soon as the Sun is at an angle of less than 20 degrees above the horizon, and that explains the phenomenal groundwave daytime DX that AM broadcast band Dxers are reporting.

This is Radio Havana Cuba, the name of the program is Dxers Unlimited, and here is our next item:

The latest statistics of Spotless Days
Current Stretch: 432 days
2009 total: 184 days (79%)
Since 2004: 695 days
Typical Solar Min: 485 days

We are having to deal with an extremely QUIET SUN: According to sunspot counts, the longest stretch of spotless suns during the current solar minimum was 52 days in July, August and Sept. of 2008.

The current sequence of totally blank, spotless, suns is putting that record in jeopardy.

The sun is entering its 43rd consecutive day with no sunspots, and there are none in the offing.

The Very Deep new solar minimum continues.We are now having to deal with an extremely weak ionosphere, that is incapable of sending back to Earth radio signals above 20 megaHertz for most of the time... So in actual practice any radio signals that are transmitted on frequencies higher than 20 megaHertz are automatically going out into space without practically any attenuation at all.

The most recent scientific results related to solar activity are concentrating on the research done by American solar experts Bill Livingston and Matt Penn that work at the National Solar Observatory in Tucson, Arizona. They have published a report stating that the sunspot magnetic fields are waning. The two well respected solar astronomers have been measuring solar magnetism since 1992.

Their sophisticated technique is based on Zeeman splitting of infrared spectral lines emitted by iron atoms in the vicinity of sunspots. If their results are extrapolated into the future, everything points to the fact that sunspots may be less and less frequenct as we enter into what could be another Maunder minimum.

While the data collected and analyzed by Livingston and Penn are widely thought to be correct, far-reaching extrapolations may be premature. This type of measurement is relatively new, and the data reaches back less than 17 years, actually less than two solar cycles, or a single bipolar cycle, whichever way you like to see it .

The two scientists have stated that a long term sunspot decline , analogous to the Maunder minimum, remains to be seen... But they have certainly introduced a new approach to the analysis of the extended present period of very low solar activity. As a good friend of mine recently said, one must get ready for the very low sunspot counts , and the only way to be well prepared is by installing highly efficient low frequency band antennas, capable of operating from 500 kiloHertz to 10 megaHertz.

For amateur radio operators interested in enjoying the hobby to its full extend during the extended solar minimums, antennas to be explored include large than usual size magnetic loops,capacity hat top loaded verticals and the now extremely popular among AM broadcast stations folded monopoles.

I am sorry to say that Dxing opportunities on the 20 meters band are going to be rather few and far spaced, while amateur bands above 18 megaHertz will very rarily be open via F2 layer propagation.

Stay tuned for more radio hobby related information amigos... I'll be back with you in a few seconds after a short break for station ID.

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This is Radio Havana Cuba , the name of the show is Dxers Unlimited, and here is our next radio hobby related item...

How even with a very simple , easy to homebrew amateur radio transceiver operating on the 40 meters ham band with a low gain antenna, it is possible to work DX stations half way around the world, under the worst ever propagation conditions seen amateur radio operators since the very early days of radio more than a century ago.

With a power output of about 25 Watts, the transmitter module of my Super Islander transceiver is capable of sending both CW Morse Code radiotelegraphy signals as well as double sideband suppressed carrier voice signals.

Using the CW mode of the Super Islander during our local evenings , it is possible to contact stations in Europe and Africa, and sometimes even as far as the Middle East. Later after about two o'clock in the morning local time here in Havana, stations from Australia, New Zealand and Japan start to come in, and one can contact them until shortly after sunrise.

The Japanese CW operators are characterized by their very clear sending, something that makes reception a lot easier than when one has to deal with operators that don't send the Morse Code characters with the proper spacing between them, as well as between words.

Yes, 25 Watts into a half wave dipole , is all that is required during the peak propagation periods, when DX is coming in despite the extremely low solar activity. The 40 meters band continues to be , in my opinion, the best all around compromise for ham radio operators that come back from work after five PM local time !!!

For those of you that are retired, or work the night shift, HF propagation conditions do open up on 20 meters and even on the 17 meters band for a few hours, but due to the extremely low solar activity those openings don't last long.

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Si amigos, here is once again, the section of Dxers Unlimited that you have rated as the number one most popular of them all.... ASK ARNIE, answering your radio hobby related questions via e-mail directly and also on the air for the benefit of other listeners that may want also to learn about the same problem...

ASK ARNIE today will be answering a question sent by listener Michael from Berlin , Germany about a simple transmitter circuit that he recently read about...

The Jones Push Pull oscillator ... Well amigo Michael, all I can say is that the Jones Push Pull crystal controlled oscillator is one of the most amazingly reliable , easy to homebrew and a delight to operate little transmitter.

I have built several of them here, using small receiving type dual triodes vacuum tubes , like the ECC81 or 12AT7 or its Russian equivalent , and results are always excellent. My latest Jones Push Pull rig was made using two triode connected 6V6 tetrodes, that work nicely on the 40 meters band , providing about 10 Watts output of very nice clean CW.

The low parts count of the Jones circuit is something to be considered too, as well as the fact that it is ideal for breadboard mounting, making it a very attractive rig to display so that visitors to your shack may enjoy the art of radio at its best.

I have tested the Jones Push Pull oscillator transmitter on frequencies as high as 10 megaHertz , that is the 30 meters amateur band that spans from 10.1 to 10.15 megaHertz, and just recently I modified the plate coil to make it work on the 14 megaHertz or 20 meters band, using a 14.032 quartz crystal that oscillates strongly .

The only problem with the 20 meters rig is that it does chirp a little bit, something that is not present of the other rigs tested on 160, 80, 40 and 30 meters bands.

The Jones Push Pull vacuum tubes oscillator dates back to the early days of amateur radio amigos.

Breadboard construction, and a simple voltage doubler power supply will make possible to assemble a replica of one of these rigs capable of providing many hours of enjoyment , and you will be surprised when people ask you for details of the Jones Push Pull rig once you tell them that they are listening to a homebrew rig.

As a matter of fact, just mentioning that your rig is homebrew generated a lot of attention from amateur operators all around the world , who unfortunately are relying more and more on across the counter , ready to operate transceivers full of bells and whistles, but without the charm that only homebrew radios can give you !!!

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And now amigos, as always at the end of the show, here is your friend Arnie Coro's Dxers Unlimited HF plus low band VHF propagation update and forecast.... Its over now, that is, the summer sporadic E season, as expected is for all practical purposes over after the Perseids meteor shower...

I don't mean that there is a connection , but records show that after the third week of August sporadic E openings are few and spaced far between them.

Solar activity at rock bottom levels with now almost 44 consecutive days without a single sunspot seen... so we are dealing with a very weak ionosphere, very low ionospheric absorption and as expected the daytime maximum useable frequency curve shows a very slow rise after daybreak, barely reaching 20 megaHertz at the best moments on the most favorable paths.

I hope to have you all listening to the mid week edition of Dxers Unlimited that will be coming to you next Tuesday and Wednesday UTC days amigos !!! AND, don't forget to send me your comments about this program to inforhc at enet dot cu or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba..

Dxers Unlimited's mid week edition 11-12 August 2009

Radio Havana Cuba

Dxers Unlimited's mid week edition for 11-12 August 2009

By Arnie Coro

Radio Amateur CO2KK

Hi amigos radioaficionados around the world and orbiting Planet Earth....This is the mid week edition of your favorite radio hobby program,coming to you from Havana,the capital city of Cuba...I am Arnie Coro,radio amateur CO2KK,and here is our first news item of today's program....

Headline: Thirty one consecutive days without a single sunspot seen on the solar disc... Yes, you have heard it correctly... a month and a day without a single sunspot seen by scientists keeping the solar patrol watch active 24 hours a day.

The total number of days of this year 2009 without a single sunspot seen has no increased to 173, that putting it in a somewhat more easy to undertand form means that seventy eight percent of this year has gone by without sunspots.

So, we are well into an extended solar minimum.

If we go to the year 2004 when solar cycle number 23 started its downward phase, the total number of spotless days recorded has reached the amazing figure of six hundred and eighty four days, a number well above the typical solar minimum spotless days that is four hundred and eighty five..

Again, and to underscore the terrible impact on short wave propagation that the present extended solar minimum has had, here are some of the practical results of this outstanding lack of solar activity that include , in the first place, a very low daytime F2 layer maximum useable frequency, as expected also comes associated with a very low ionospheric noise level.

This is Radio Havana Cuba, the name of the program is Dxers Unlimited, and here is our next item:

As requested by many Dxers Unlimited's listeners, a detailed explanation about SUNSPOTS ,that hopefully will be simple enough to be understood by non scientists.,

The Sunspot Number

Scientists track solar cycles by just carefully counting sunspots –the solar sunspots are cool planet-sized areas on the Sun where intense magnetic fields come up through the star's visible surface, cool enough to make them look dark, hence the name sunspots.

Counting sunspots is not as simple and straightforward as one may think.

Lets imagine that you looked at the Sun through a pair of (properly filtered) low power binoculars -- you might be able to see two or three large spots.

An observer using a professional astronomical high-power telescope might see 10 or 20 sunspots. If we go further into better instruments located at ideal locations, a powerful space-based solar observatory could see even more -- say, 50 to 100. So there is something that is very confusing...

Which is the correct sunspot number?

The world's scientific community has accepted two official sunspot numbers that are in common use. The first, the daily "Boulder Sunspot Number," is computed by the National Oceanic and Atmospheric Administration of the United States of America's Space Environment Center by using a formula devised by astronomer Swiss Rudolph Wolf in 1848:

R=k (10g+s),

where R is the sunspot number; g is the number of sunspot groups on the solar disk; s is the total number of individual spots in all the groups; and k is a variable scaling factor (usually <1) that accounts for observing conditions and the type of telescope (binoculars, space telescopes, etc.).

Scientists combine data from lots of observatories -- each with its own k factor -- to arrive at a daily value.

The Boulder number usually about 25% higher than the second official index, the "International Sunspot Number," published daily by the Solar Influences Data Center in Belgium. Both the Boulder and the International numbers are calculated from the same basic formula, but they incorporate data from different observatories.

Interestingly, and as a rule of thumb, if you divide either of the official sunspot numbers by 15, you'll get the approximate number of individual sunspots visible on the solar disk if you look at the Sun by projecting its image on a paper plate with a small telescope.

More radio hobby related information in a few seconds when Dxers Unlimited's mid week edition continues after a short break for station ID amigos ... I am Arnie Coro in Havana...

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You are listening to Radio Havana Cuba, the name of the show is Dxers Unlimited, it's our twice weekly small contribution to the development of this wonderful hobby that has existed now for more than a century : RADIO...

Here is now our next item of today's program: Forty three city of Havana radio amateur operators met at the venue of the Cerro Radio Club with the purpose of organizing a group aiming at promoting the use of radiotelegraphy... And when we talk about radiotelegraphy , we mean, as the group's organizer and later elected as its coordinator CO2FU Carlos Fonseca said, we are talking about acoustically received CW Morse Code, sent using hand operated devices... in the most deeply rooted tradition of radio communications.

Fonseca who is an exceptionally good CW operator himself also said that anyone that enjoys operating CW is most welcome to become a member of the new group , no matter at what speed she or he can receive and transmit using CW radiotelegraphy.

Among the participants at the first meeting I found long time friends that are often heard on the air working DX on CW, as well as several of the newcomers to the HF bands , just starting to learn how to hunt for those really hard to work DX expeditions.

One of the first decisions adopted by the group members was to provide newcomers with CW Morse Code practice on the two meters band, so that they can pick up receiving speed.

My perception was that this enthusiastic group of radio amateurs will make possible that many operators that pass the second class amateur radio license test will be able to go on the air on the HF bands, especially 40 and 20 meters , soon after their license upgrade.

Another positive step was designating one of the participants as the technical secretary of the City of Havana Radio Telegraphy Group, who will have among his duties working on a prototype simple CW single band transmitter, that may be built using locally available parts.

If you operate on the 40 meters band DX window, between 7000 and 7030 kiloHertz, there are good chances that you will be able to work not one but several Cuban stations , and from now on I foresee an increase in the number of CM and CO prefix stations that will be on the air using CW.

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This is Dxers Unlimited and now , our technical topics section... During the Sunday meeting at the Cerro Radio Club in downtown Havana, several of the participants asked yours truly about the possibility of designing a simple, easy to build, low parts count , single band amateur radio transmitter designed to operate as a CW Morse Radiotelegraphy only rig... As soon as I returned from the meeting, a new notebook was started , to serve as the record keeping place for the project.

The first step was to write down the specifications of the CW transmitter, something that very soon led to not one , but two different approaches... actually three, if you consider a hybrid transmitter too.

Project one, will make the best possible use of existing vacuum tubes no longer in use, but still in like new condition, that are plentiful locally and cost nothing or next to nothing...

Project two, a somewhat more sophisticated and modern approach calls for an all solid state rig in the 20 to 30 Watts input power class, and finally, it was obvious that a third approach was also possible, by designing a hybrid rig, using transistors for the variable frequency oscillator and vacuum tubes for the driver and power amplifier stages.

One big drawback for us here is the lack of quartz crystals for the low end of the 40 meters band, where CW DX activity is found.

If we had crystals on frequencies between 7005 and 7035 kiloHertz, an ultra simple vacuum tube CW transmitter could be built during a single weekend...

But, we don't have those quartz crystals, so the next option is to design and build a high quality transistorized VFO or variable frequency oscillator, a task that is certainly not for beginners...

Anyway, as one of the City of Havana Radio Telegraphy Group founders also said at its first meeting, there are several highly qualified radio enginneers and technicians that form part of our group, and could be in charge of designing the prototype of the VFO, and later go ahead adding power amplifier stages as well as power supplies for the rigs.

So far, just two days after our first meeting, we are hearing more CW activity on 40 meters, as local hams are gathering on 7050 kiloHertz to provide practice to the newcomers that are able to listen on that band...

Also, at my home workshop, the first prototype VFO is already taking shape... and a box now almost half full of parts to be used in the project.

For those of you that have already enjoyed the unique pleasure of making a two way amateur radio contact with a piece of equipment that you have built all by yourself, it is not difficult to understand why so many hams here are asking when the first protype 40 meters band rig will be ready for testing.

So far, the power supply is almost finished... it will provide fully regulated 12 volts DC for the variable frequency oscillator, 18 volts for the also solid state pre-driver stage and all the required AC and DC voltages for operating the two vacuum tubes class C amplifier stages.

The prototype rig will use a locally available Russian high gain pentode for the driver stage that was used by an old TV set, and that same TV set's horizontal output stage tetrode will be the output stage.

No attempt will be made to make this a small or miniature rig... what we want to achieve is an easy to build and to repair CW transmitter , that will provide up to 50 Watts output power if required, but that will normally be operated at between 10 and 30 Watts, depending on the available high voltage power supply.

Amigos, this is a nice project that will make possible for many Cuban amateurs to go on the air with their own CW station, develop their operating skills and work many of the most popular world contests...

And now amigos , as always at the end of the program, here is your friend Arnie Coro's HF propagation update and forecast... A new updated forecast for solar cycle 24 is stating that it is going to start between March and May of 2010... Yes, that's right, several well known solar scientists are now practically sure that the new solar cycle hasn't even started yet, something that for me is very , very difficult to understand, because some of the sunspots seen since early 2008 had the magnetic polarity of a new cycle and were located at high solar latitudes... Anyway, the revised update for solar cycle 24 also says that the peak will be one year later than what was previously expected, taking place during mid 2013, and it would only be reaching an average of 90 sunspots during the peak months ...

Present solar flux is at rock bottom levels of 66 to 68 units and we are dealing with an extremely weak ionosphere during the next several weeks.

Don't forget to set aside a little time to send your comments about today's edition of Dxers Unlimited. Send e-mail to inforhc at enet dot cu, again, inforhc at enet dot cu and VIA AIRMAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba.

Sunspot number: 0

Updated 10 Aug 2009

Spotless Days
Current Stretch: 31 days
2009 total: 173 days (78%)
Since 2004: 684 days
Typical Solar Min: 485 days