Radio Havana Cuba
Dxers Unlimited's middle of the week edition for Tuesday
June 7 UTC day
By Arnie Coro
radio amateur CO2KK
Hola amigos.... lots of rain here in Havana during the past several days as the weather system that gave birth to tropical storm Colin formed very near to Cuba. Rainfall levels of as much as four inches fell at the extreme western end of Cuba and also at the Isle of Youth, requiring
the activation of amateur radio emergency communications nets .
The weather continues to be overcast and rainy here in La Habana and all over western Cuba, but the rate of rainfall has diminished .
Ham radio operators always are ready to provide alternative emergency communications whenever they are required... it does not need for a tropical storm to enter your area to require communications assistance when local floods happen.
The use of portable battery operated hand held and mobile transceivers on the 2 meters band provides excellent local coverage, especially if a mountain top or a high rise building repeater station is available.
Among Cuban radio amateurs the use of portable easy to assemble small Yagi antennas proves to be very effective to reach longer distances than those that can be reached using the portable handy talkies factory built short vertical monopole antennas.
Another thing we have learned about batteries is that computer UPS power units GEL CELL accumulators work very well and provide much longer service than the radio's plug in batteries...
Home built battery chargers with three different charging rates are popular among the emergency backpacks that most Cuban radio amateurs always keep ready to provide communications whenever needed....
I am Arnaldo, Arnie Coro, radio amateur CO2KK, this is Dxers Unlimited's middle of the week edition and here is item two of our program....
Four days without a single sunspot in sight... yes, a totally blank Sun since the third day of June has kept scientists scratching their heads forthe last four days...
Heliophysicists are now trying to figure out it this four days without sunspots are signalling a much earlier than expected end of solar cycle 24, that according to forecasters should be coming to an end by in about two years, when many days of zero sunspots counts are going to happen....
Item three: How many optical telescopes are now aiming at the Sun trying to find the first sunspot to appear after the four days of a blank Sun.... It will be difficult to estimate but all I can say is that
amateur astronomers all around the world are trying to be the first one to report a new sunspot, in full competition with professional observers....
All they have seen so far is a rather large solar coronal hole that is sending to Earth a stream of charged particles disturbing the otherwise very quiet ionosphere....
Now item four: Also related to the period of extremely low solar activity.... This is certainly the right moment to monitor for the presence of higher than usual frequency of Sporadic E events... because
there are some theories that relate the periods of very low solar activity to an actual increase in the number and duration fo sporadic E layer events...
So please keep a close watch for short skip on the 20 and 15 meters amateur bands and for DX signals on the 10 and 6 meter bands that will come from sporadic E layer openings....
Si amigos, sure, I am always looking for original circuit diagrams that can be described as using the minimum possible number of parts.
And although the one I am about to describe does need a quartz crystal capable of operating on one of the CW segments of 40 or 30 meters, it has proven to be among the simplest to build and easiest to get going transmitter-receiver combos....
Yes, it is not a transceiver as such... but it does use some common parts.
The transmitter module was built and tested first, and used on the air on 7053 kiloHertz, the only quartz crystal that I had at hand in my workshop to run the test.
The power supply , built on separate chassis without any attempt to make if a miniature piece of electronic equipment, is one of the now three identical ones that are at hand.
It provides several alternating current voltages for running the vacuum tubes filaments and the direct current voltage required for the plate and screen grids... It also provides negative bias , a very convenient feature for experimenting ....
The transmitter module uses a single tetrode vacuum tube, that is capable of delivering several Watts to the antenna . It is keyed by inserting the radiotelegraphy key between the cathode and ground.
A very simple circuit that uses few parts, and that will start oscillating even with very sluggish crystals.
Ideally you should aim at obtaining quartz crystals for 40 meters within the range between 7000 and 7040 kiloHertz, and between 7100 and 7125 kiloHertz.
You will want to use older sturdy crystals , like the still found FT243 World War II vintage rocks.
Despite the not so good frequency in my test rig... 7053 kiloHertz several stations have come back to my CQ DX calls and provided reports as good as a 579 from Texas and a 559 from New York... not too bad considering that no more than 5 or maybe 6 Watts are going to the wire dipole antenna on my roof.
The transmitter module is now awaiting for the cabinet , where it would fit side by side with the receiver module.
For those of you interested in this home brew project using recycled or new old stock vacuum tubes, I will soon be making available the circuit diagrams, building instructions and some photos so that you can easily duplicate this QRP or low power amateur 40 meters band station.
By the way, as solar cycle 24 continues its downward trend 40 meters is going to become an excellent amateur band for night time operation !!!
Now let's take a look at the receiver. Originally it was going to be a single tube regenerative , but it ended with one more triode-tetrode tube added to boost the audio output.
The detector tube I am using is my favorite screen grid controlled Hartley , using the 6AK5 or 5654 pentode, or the Russian clone 6ZHE1P equivalent... The audio tube is a ECL82 or 6BM8 that provides excellent quality and loudspeaker volume .
So we have ended up with a three vacuum tubes 40 meters band amateur station, although in actual practice there are four active devices... because the ECL82 or 6BM8 includes two tubes inside the same glass envelope, one that is a triode and the other the output tetrode.
The external power supply unit uses silicon diode rectifiers and high capacitance electrolytics plus a voltage regulator to provide stabilized voltage to the detector tube.
The receiver is very sensitive and I can pick up very weak stations with it... In the first upgrade to the power supply I added a regulated 6.3 volts DC module that is feeding the filaments of the 6AK5 regenerative detector tube and the filaments of the ECL82 something that keeps the background audio hum levels to very low values....
A preliminary parts count for the complete project includes it into the less than 100 components category, and I can also add that there are no rare , hard to find or unobtanium parts used.
As a matter of fact, many parts can be replaced with approximate values and the self contained CW statation will continue to perform very well....
Now, I can add that it can also be used on the 30 meters amateur band, by using the proper quartz crystal for the transmitter and changing the tuned circuit values for the regenerative detector ....
I was asked by a local radio amateur who recently saw the now almost complete project why it was not designed to use solid state components, and my answer was that here in Cuba we have a large number of vacuum tubes from old TV sets and parts from them that cost nothing and can
work very well for many years to come.
All that said, he started to ask me for parts in my junk box , and also we went upstairs to look for the hand drawn schematics in order to copy them for him .... soon we may have several of these easy to build and tune up 40 meter band stations in operation from Cuba....At the end of the show: An update about solar activity was included...!!!!
By Arnie Coro
radio amateur CO2KK
Hola amigos.... lots of rain here in Havana during the past several days as the weather system that gave birth to tropical storm Colin formed very near to Cuba. Rainfall levels of as much as four inches fell at the extreme western end of Cuba and also at the Isle of Youth, requiring
the activation of amateur radio emergency communications nets .
The weather continues to be overcast and rainy here in La Habana and all over western Cuba, but the rate of rainfall has diminished .
Ham radio operators always are ready to provide alternative emergency communications whenever they are required... it does not need for a tropical storm to enter your area to require communications assistance when local floods happen.
The use of portable battery operated hand held and mobile transceivers on the 2 meters band provides excellent local coverage, especially if a mountain top or a high rise building repeater station is available.
Among Cuban radio amateurs the use of portable easy to assemble small Yagi antennas proves to be very effective to reach longer distances than those that can be reached using the portable handy talkies factory built short vertical monopole antennas.
Another thing we have learned about batteries is that computer UPS power units GEL CELL accumulators work very well and provide much longer service than the radio's plug in batteries...
Home built battery chargers with three different charging rates are popular among the emergency backpacks that most Cuban radio amateurs always keep ready to provide communications whenever needed....
I am Arnaldo, Arnie Coro, radio amateur CO2KK, this is Dxers Unlimited's middle of the week edition and here is item two of our program....
Four days without a single sunspot in sight... yes, a totally blank Sun since the third day of June has kept scientists scratching their heads forthe last four days...
Heliophysicists are now trying to figure out it this four days without sunspots are signalling a much earlier than expected end of solar cycle 24, that according to forecasters should be coming to an end by in about two years, when many days of zero sunspots counts are going to happen....
Item three: How many optical telescopes are now aiming at the Sun trying to find the first sunspot to appear after the four days of a blank Sun.... It will be difficult to estimate but all I can say is that
amateur astronomers all around the world are trying to be the first one to report a new sunspot, in full competition with professional observers....
All they have seen so far is a rather large solar coronal hole that is sending to Earth a stream of charged particles disturbing the otherwise very quiet ionosphere....
Now item four: Also related to the period of extremely low solar activity.... This is certainly the right moment to monitor for the presence of higher than usual frequency of Sporadic E events... because
there are some theories that relate the periods of very low solar activity to an actual increase in the number and duration fo sporadic E layer events...
So please keep a close watch for short skip on the 20 and 15 meters amateur bands and for DX signals on the 10 and 6 meter bands that will come from sporadic E layer openings....
Si amigos, sure, I am always looking for original circuit diagrams that can be described as using the minimum possible number of parts.
And although the one I am about to describe does need a quartz crystal capable of operating on one of the CW segments of 40 or 30 meters, it has proven to be among the simplest to build and easiest to get going transmitter-receiver combos....
Yes, it is not a transceiver as such... but it does use some common parts.
The transmitter module was built and tested first, and used on the air on 7053 kiloHertz, the only quartz crystal that I had at hand in my workshop to run the test.
The power supply , built on separate chassis without any attempt to make if a miniature piece of electronic equipment, is one of the now three identical ones that are at hand.
It provides several alternating current voltages for running the vacuum tubes filaments and the direct current voltage required for the plate and screen grids... It also provides negative bias , a very convenient feature for experimenting ....
The transmitter module uses a single tetrode vacuum tube, that is capable of delivering several Watts to the antenna . It is keyed by inserting the radiotelegraphy key between the cathode and ground.
A very simple circuit that uses few parts, and that will start oscillating even with very sluggish crystals.
Ideally you should aim at obtaining quartz crystals for 40 meters within the range between 7000 and 7040 kiloHertz, and between 7100 and 7125 kiloHertz.
You will want to use older sturdy crystals , like the still found FT243 World War II vintage rocks.
Despite the not so good frequency in my test rig... 7053 kiloHertz several stations have come back to my CQ DX calls and provided reports as good as a 579 from Texas and a 559 from New York... not too bad considering that no more than 5 or maybe 6 Watts are going to the wire dipole antenna on my roof.
The transmitter module is now awaiting for the cabinet , where it would fit side by side with the receiver module.
For those of you interested in this home brew project using recycled or new old stock vacuum tubes, I will soon be making available the circuit diagrams, building instructions and some photos so that you can easily duplicate this QRP or low power amateur 40 meters band station.
By the way, as solar cycle 24 continues its downward trend 40 meters is going to become an excellent amateur band for night time operation !!!
Now let's take a look at the receiver. Originally it was going to be a single tube regenerative , but it ended with one more triode-tetrode tube added to boost the audio output.
The detector tube I am using is my favorite screen grid controlled Hartley , using the 6AK5 or 5654 pentode, or the Russian clone 6ZHE1P equivalent... The audio tube is a ECL82 or 6BM8 that provides excellent quality and loudspeaker volume .
So we have ended up with a three vacuum tubes 40 meters band amateur station, although in actual practice there are four active devices... because the ECL82 or 6BM8 includes two tubes inside the same glass envelope, one that is a triode and the other the output tetrode.
The external power supply unit uses silicon diode rectifiers and high capacitance electrolytics plus a voltage regulator to provide stabilized voltage to the detector tube.
The receiver is very sensitive and I can pick up very weak stations with it... In the first upgrade to the power supply I added a regulated 6.3 volts DC module that is feeding the filaments of the 6AK5 regenerative detector tube and the filaments of the ECL82 something that keeps the background audio hum levels to very low values....
A preliminary parts count for the complete project includes it into the less than 100 components category, and I can also add that there are no rare , hard to find or unobtanium parts used.
As a matter of fact, many parts can be replaced with approximate values and the self contained CW statation will continue to perform very well....
Now, I can add that it can also be used on the 30 meters amateur band, by using the proper quartz crystal for the transmitter and changing the tuned circuit values for the regenerative detector ....
I was asked by a local radio amateur who recently saw the now almost complete project why it was not designed to use solid state components, and my answer was that here in Cuba we have a large number of vacuum tubes from old TV sets and parts from them that cost nothing and can
work very well for many years to come.
All that said, he started to ask me for parts in my junk box , and also we went upstairs to look for the hand drawn schematics in order to copy them for him .... soon we may have several of these easy to build and tune up 40 meter band stations in operation from Cuba....At the end of the show: An update about solar activity was included...!!!!
(Arnie Coro/R Habana Cuba)
