Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited’s mid week edition for February 6-7 2007
By Arnie Coro
CO2KK
Hi amigos radioaficionados, with our traditional salute to those of you that are listening to this radio hobby program around the world, it’s my pleasure to share with you about seventeen minutes of air time, and also we are now regularly on the the world wide web with streaming audio from our website www.radiohc.cu, from 05 to 07 hours UTC…
Now here is item one, our number one most popular section of the show…
ASK ARNIE, that today is answering a letter that came via e-mail from Atlanta, Georgia, USA. Here is the letter…
Dear Arnie:
I heard your show on Saturday February 3, 2007 and found it very interesting. Reception in Atlanta was excellent. In particular the segment about front end filters and amplifiers. Could you please email to me a copy of the materials describing your filters and amplifiers.
Thank you.
Signed
Joseph
Now here is part one of my answer to amigo Joseph…
Dear amigo:
Thanks for the reception report.It would be nice to know on what frequency you had such an excellent reception...as we are using several frequencies to your part of the world, and also the show is on the air at different times of the day. As regards to your request, I will send you detailed information about the "boxes" that I have designed and built to improve short wave
receivers front ends,including the schematic diagrams. I also use them on my homebrew receivers with excellent results. First of all you and all short wave listeners must realize that there are huge signals now present all along the short wave spectrum, that come from very powerful transmitters running up to 500 and even 1000 kiloWatts that are then connected to antenna systems that concentrate the power into a very limited target area, so the so called effective radiated power may be in some cases up to 100 megaWatts, or one hundred
million Watts !!!
So, radio receivers have to deal with those huge signals at their input a problem that becomes especially difficult when the radio is connected to a large size external antenna. Signals present at the antenna input terminals of the receiver are really significant, and they may generate many problems, like something known as cross modulation , that makes reception of the desired station practically impossible because the very powerful signal from another station mixes with the desired station making listening extremely difficult.
That's why even a very simple antenna input attenuator connected between the external antenna and the radio receiver helps so much in providing better reception. Even a good quality carbon potentiometer of between 500 and 2000 ohms will help a lot to improve reception, especially in the case of low cost receivers that don't have very good front end
selectivity.
A better option is a resistive STEP ATTENUATOR, that may even be calibrated in DECIBELS OF ATTENUATION , something that may prove to be quite helpful in assesing the signal strength of different stations. The STEP ATTENUATOR that I use here is calibrated in the following steps 0 dB attenuation, that is antenna connected directly to the receiver's
antenna input 3 dB attenuation, that meaning that half of the signal power is attenuated
10 dB attenuation, that meaning that the signal reaching the receiver is one tenth of the signal available at the input 20 dB attenuation , that meaning that the signal reaching the receiver
is one hundred times less than the signal at the input of the attenuator and finally 30 dB , which is rarely used, but still useful when doing some tests, and , of course 30 dB means that the power available at the receiver's antenna terminals is one thousand times less than at the input of the attenuator.
It is really amazing to operate a low cost portable short wave receiver using a properly connected external antenna via an input resistive attenuator.
In another e-mail and also here, on the air , for the benefit of other Dxers Unlimited’s listeners, I will describe the tuneable bandpass input filters that will complete my "number one box".... a piece of equipment that for some odd reasons no commercial manufacturer of radio accesories is offering to the worldwide radio hobby community, making it necessary for individuals to homebrew them...
Now standby for a few seconds , a station ID follows…
I am Arnie Coro , radio amateur CO2KK in Havana, stay right on this frequency or keep connected to www.radiohc.cu
Amigos !!!
………………
This is Radio Havana Cuba, the name of the show is Dxers Unlimited, and yes amigos, we do QSL, we do verify reception reports with a beautiful QSL card that is sent VIA AIR MAIL and absolutely free of charge, as we believe that every international short wave station must QSL to its listeners as a nice thank you gesture for listening !!! Now here is item two of this mid week edition of the program…The also very popular antenna topics section… Monday afternoon I had a nice two way contact with CO3LE , Eduardo, who is an amateur radio operator that lives about 50 miles away from my home. I had perfect copy from his low power two meters band amateur station, and when I asked him what he had done to improve his signal into the Cuban capital so much, he replied that he had just finished building and installing a nine elements Yagi antenna that I designed several years ago for my son Arnie Junior CM2KW amateur radio station. Eduardo CO2LE reduced the power output of his FM two meters band transceiver to just one Watt and I was still able to copy him with my zero dB gain omnidirectional antenna.
This nine element Yagi antenna does need a rotor , because its radiation pattern is very sharp, requiring that it be aimed very precisely to the station you want to contact. Eduardo , who is a very good mechanic also, has designed and built a homebrew rotor using a large truck’s windshield wiper motor, to which he added a control box and power supply, as well as stop limit switches… The 24 volts DC motor has a gear train with a very large ratio of revolutions delivered by the motor to the revolutions delivered by the gear train , so the antenna takes about one and half minutes to sweep around the 360 degrees of the compass, that is a very speed for turning around a directional antenna system… faster speeds make aiming the antenna difficult, and slower ones will take a very long time to complete one revolution…Given the high cost of antenna rotors , Eduardo’s project may prove to be a very attractive option for
radio hobby enthusiasts that also enjoy doing mechanical work…
Dxers Unlimited
Dxers Unlimited’s mid week edition for February 6-7 2007
By Arnie Coro
CO2KK
Hi amigos radioaficionados, with our traditional salute to those of you that are listening to this radio hobby program around the world, it’s my pleasure to share with you about seventeen minutes of air time, and also we are now regularly on the the world wide web with streaming audio from our website www.radiohc.cu, from 05 to 07 hours UTC…
Now here is item one, our number one most popular section of the show…
ASK ARNIE, that today is answering a letter that came via e-mail from Atlanta, Georgia, USA. Here is the letter…
Dear Arnie:
I heard your show on Saturday February 3, 2007 and found it very interesting. Reception in Atlanta was excellent. In particular the segment about front end filters and amplifiers. Could you please email to me a copy of the materials describing your filters and amplifiers.
Thank you.
Signed
Joseph
Now here is part one of my answer to amigo Joseph…
Dear amigo:
Thanks for the reception report.It would be nice to know on what frequency you had such an excellent reception...as we are using several frequencies to your part of the world, and also the show is on the air at different times of the day. As regards to your request, I will send you detailed information about the "boxes" that I have designed and built to improve short wave
receivers front ends,including the schematic diagrams. I also use them on my homebrew receivers with excellent results. First of all you and all short wave listeners must realize that there are huge signals now present all along the short wave spectrum, that come from very powerful transmitters running up to 500 and even 1000 kiloWatts that are then connected to antenna systems that concentrate the power into a very limited target area, so the so called effective radiated power may be in some cases up to 100 megaWatts, or one hundred
million Watts !!!
So, radio receivers have to deal with those huge signals at their input a problem that becomes especially difficult when the radio is connected to a large size external antenna. Signals present at the antenna input terminals of the receiver are really significant, and they may generate many problems, like something known as cross modulation , that makes reception of the desired station practically impossible because the very powerful signal from another station mixes with the desired station making listening extremely difficult.
That's why even a very simple antenna input attenuator connected between the external antenna and the radio receiver helps so much in providing better reception. Even a good quality carbon potentiometer of between 500 and 2000 ohms will help a lot to improve reception, especially in the case of low cost receivers that don't have very good front end
selectivity.
A better option is a resistive STEP ATTENUATOR, that may even be calibrated in DECIBELS OF ATTENUATION , something that may prove to be quite helpful in assesing the signal strength of different stations. The STEP ATTENUATOR that I use here is calibrated in the following steps 0 dB attenuation, that is antenna connected directly to the receiver's
antenna input 3 dB attenuation, that meaning that half of the signal power is attenuated
10 dB attenuation, that meaning that the signal reaching the receiver is one tenth of the signal available at the input 20 dB attenuation , that meaning that the signal reaching the receiver
is one hundred times less than the signal at the input of the attenuator and finally 30 dB , which is rarely used, but still useful when doing some tests, and , of course 30 dB means that the power available at the receiver's antenna terminals is one thousand times less than at the input of the attenuator.
It is really amazing to operate a low cost portable short wave receiver using a properly connected external antenna via an input resistive attenuator.
In another e-mail and also here, on the air , for the benefit of other Dxers Unlimited’s listeners, I will describe the tuneable bandpass input filters that will complete my "number one box".... a piece of equipment that for some odd reasons no commercial manufacturer of radio accesories is offering to the worldwide radio hobby community, making it necessary for individuals to homebrew them...
Now standby for a few seconds , a station ID follows…
I am Arnie Coro , radio amateur CO2KK in Havana, stay right on this frequency or keep connected to www.radiohc.cu
Amigos !!!
………………
This is Radio Havana Cuba, the name of the show is Dxers Unlimited, and yes amigos, we do QSL, we do verify reception reports with a beautiful QSL card that is sent VIA AIR MAIL and absolutely free of charge, as we believe that every international short wave station must QSL to its listeners as a nice thank you gesture for listening !!! Now here is item two of this mid week edition of the program…The also very popular antenna topics section… Monday afternoon I had a nice two way contact with CO3LE , Eduardo, who is an amateur radio operator that lives about 50 miles away from my home. I had perfect copy from his low power two meters band amateur station, and when I asked him what he had done to improve his signal into the Cuban capital so much, he replied that he had just finished building and installing a nine elements Yagi antenna that I designed several years ago for my son Arnie Junior CM2KW amateur radio station. Eduardo CO2LE reduced the power output of his FM two meters band transceiver to just one Watt and I was still able to copy him with my zero dB gain omnidirectional antenna.
This nine element Yagi antenna does need a rotor , because its radiation pattern is very sharp, requiring that it be aimed very precisely to the station you want to contact. Eduardo , who is a very good mechanic also, has designed and built a homebrew rotor using a large truck’s windshield wiper motor, to which he added a control box and power supply, as well as stop limit switches… The 24 volts DC motor has a gear train with a very large ratio of revolutions delivered by the motor to the revolutions delivered by the gear train , so the antenna takes about one and half minutes to sweep around the 360 degrees of the compass, that is a very speed for turning around a directional antenna system… faster speeds make aiming the antenna difficult, and slower ones will take a very long time to complete one revolution…Given the high cost of antenna rotors , Eduardo’s project may prove to be a very attractive option for
radio hobby enthusiasts that also enjoy doing mechanical work…
He has promised to bring to Havana on his next trip the complete diagrams of how he has built the antenna rotor using a big truck windshield wiper motor, an item that can be found in many scrap yards at very low cost or just by asking for it…
These direct current motors and their gear trains are very rugged and well built, and only second to the superb aircraft windshields wiper motors and gear trains, that are, as expected , designed and built to much higher standards…
……..
Now here at Dxers Unlimited’s mid week edition is our next item…. The technical topics section, that today will deal about a very useful radio hobby shack accessory… a variable voltage direct current power supply, capable of delivering well filtered and regulated DC between 1.5 volts
and 24 volts… a range that will provide the possibility of testing and operating a large number of electronic devices.
The prototype of this supply is capable of delivering up to 5 amperes of current, and its construction is rather simple, because it uses an integrated circuit voltage regulator that is installed on a large size heat sink. I have included two analog meters, one to measure the voltage using two scales, One from zero to five volts, and the other from zero to twenty five
volts, although recently a friend that visited my workshop suggested the use of yet another expanded scale so that the voltmeter will read from 9 to 25 volts, so that more precise adjustments could be made in that very useful voltage range.
The current meter is calibrated in five scales, ranging from 500 milliamperes to 5 amperes, so that one may have a good idea of the current drawn by the equipment connected to this variable voltage workbench power supply, something very useful when one is attempting to
do repair work, or when a nice piece of equipment is undergoing its first rounds of testing.
…….
Si amigos, yes my friends, digital communications systems are offering amateur radio operators the possibility of communicating under the very poor propagation conditions that are typical of the lowest activity phase of a solar cycle, like the conditions that we are having to deal with at
this moment, and with the much lower night time maximum useable frequencies available, we are now seeing many more stations operating on 40 meters using the very popular and rather easy to put to work PSK 31 keyboard to keyboard digital communications mode…
Stations using PSK31 on 40 meters are gathering around 7070 kiloHertz as a center frequency,and the classic waterfall display is seeing many carriers of PSK31 stations on that frequency just after sunset local time…
These direct current motors and their gear trains are very rugged and well built, and only second to the superb aircraft windshields wiper motors and gear trains, that are, as expected , designed and built to much higher standards…
……..
Now here at Dxers Unlimited’s mid week edition is our next item…. The technical topics section, that today will deal about a very useful radio hobby shack accessory… a variable voltage direct current power supply, capable of delivering well filtered and regulated DC between 1.5 volts
and 24 volts… a range that will provide the possibility of testing and operating a large number of electronic devices.
The prototype of this supply is capable of delivering up to 5 amperes of current, and its construction is rather simple, because it uses an integrated circuit voltage regulator that is installed on a large size heat sink. I have included two analog meters, one to measure the voltage using two scales, One from zero to five volts, and the other from zero to twenty five
volts, although recently a friend that visited my workshop suggested the use of yet another expanded scale so that the voltmeter will read from 9 to 25 volts, so that more precise adjustments could be made in that very useful voltage range.
The current meter is calibrated in five scales, ranging from 500 milliamperes to 5 amperes, so that one may have a good idea of the current drawn by the equipment connected to this variable voltage workbench power supply, something very useful when one is attempting to
do repair work, or when a nice piece of equipment is undergoing its first rounds of testing.
…….
Si amigos, yes my friends, digital communications systems are offering amateur radio operators the possibility of communicating under the very poor propagation conditions that are typical of the lowest activity phase of a solar cycle, like the conditions that we are having to deal with at
this moment, and with the much lower night time maximum useable frequencies available, we are now seeing many more stations operating on 40 meters using the very popular and rather easy to put to work PSK 31 keyboard to keyboard digital communications mode…
Stations using PSK31 on 40 meters are gathering around 7070 kiloHertz as a center frequency,and the classic waterfall display is seeing many carriers of PSK31 stations on that frequency just after sunset local time…
And now amigos, as always at the end of the show, here is our exclusive and not copyrighted HF plus low VHF band propagation update and forecast. Let me start my telling you that February is the month of the year with the lowest probability of Sporadic E events…, so although
sporadic E events may happen they are very rare at this time of the year. REDICTIONS FOR 06 Feb 2007 10CM FLUX: 082 / AP: 007
PREDICTIONS FOR 07 Feb 2007 10CM FLUX: 081 / AP: 010
PREDICTIONS FOR 08 Feb 2007 10CM FLUX: 081 / AP: 010
COMMENT: Solar activity was very low during the last 24 hours. No flares
above C level are expected for the next 72 hours.
Geomagnetic activity was very low during the last 24 hours. Quiet
conditions are expected for the next 78 hours. The solar wind speed
measured by the ACE spacecraft slightly increased to 400 km/s.
Optical sunspot number was at 16 on Monday,
Hope to have you all listening to Dxers Unlimited’s weekend edition amigos,and don’t forget to set aside a little time to send me
sporadic E events may happen they are very rare at this time of the year. REDICTIONS FOR 06 Feb 2007 10CM FLUX: 082 / AP: 007
PREDICTIONS FOR 07 Feb 2007 10CM FLUX: 081 / AP: 010
PREDICTIONS FOR 08 Feb 2007 10CM FLUX: 081 / AP: 010
COMMENT: Solar activity was very low during the last 24 hours. No flares
above C level are expected for the next 72 hours.
Geomagnetic activity was very low during the last 24 hours. Quiet
conditions are expected for the next 78 hours. The solar wind speed
measured by the ACE spacecraft slightly increased to 400 km/s.
Optical sunspot number was at 16 on Monday,
Hope to have you all listening to Dxers Unlimited’s weekend edition amigos,and don’t forget to set aside a little time to send me
Yours truly, signal reports and comments about today’s program to: arnie@rhc.cu, or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba.
(Arnie Coro)
(Arnie Coro)
