Radio Havana Cuba, DXers Unlimited weekend edition May 30-31, 2009
By Arnie Coro CO2KK
Hi amigos radioaficionados around the world, and the six space travelers now orbiting in space !
I am Arnie Coro radio amateur CO2KK welcoming you to my twice weekly radio hobby program that really tries to cover the more than 85 ways you and I enjoy our wonderful hobby, from participating in an exhausting whole weekend worldwide amateur radio contest like the one taking place right now, to relaxing at a the sandy beach of a tropical tourist resort listening to a far away AM broadcast band station that is heard on your little portable radio with a nice and clear signal thanks to that interesting propagation effect known among experts as sea gain...
Sure, this hobby is always challenging, and when you think that already you have gone through all the possible aspects of it, then someone comes out with a radically new antenna, a new digital communications mode using computers or suddenly finds out that there is still a lot of room for experimenting at the millimeter wavelengths...
Si amigos, yes my friends, oui mes amis in Canada and the French speaking Caribbean that listen to this program, radio is simply fascinating...
Take for example this weekend's CQ Radio Amateur magazine WPX CW contest, when thousands of amateur radio stations around the world are on the air to try to work as many new prefixes as possible...According to my own on the air on 40 meters, so far the WPX contest this weekend was quite a challenge to the participants due to the extremely low solar activity that has prevailed for the past week.
From the very beginning on Satuday at 00 UTC when the contest started, that was Friday evening for us here in the Americas, it was clear that the bands above 14 megaHertz or 20 meters would offer participants very few chances of working many stations, and as a matter of fact, fifteen and ten meters should remain totally closed for F2 mode propagation for most of the time.
So far those really rare goodies picked up on the ham bands, the really hard to work prefixes have shown up on 40 meters, because working on 160 and 80 meters has had to deal with the extremely high QRN that is atmospheric noise levels .
Other maybe not so rare, but nevertheless interesting stations heard during the weekend WPX ham radio CW contest showed up during a short lived opening on 15 meters Saturday morning my local time, when I was giving the finishing touches to the script of this program.
By Arnie Coro CO2KK
Hi amigos radioaficionados around the world, and the six space travelers now orbiting in space !
I am Arnie Coro radio amateur CO2KK welcoming you to my twice weekly radio hobby program that really tries to cover the more than 85 ways you and I enjoy our wonderful hobby, from participating in an exhausting whole weekend worldwide amateur radio contest like the one taking place right now, to relaxing at a the sandy beach of a tropical tourist resort listening to a far away AM broadcast band station that is heard on your little portable radio with a nice and clear signal thanks to that interesting propagation effect known among experts as sea gain...
Sure, this hobby is always challenging, and when you think that already you have gone through all the possible aspects of it, then someone comes out with a radically new antenna, a new digital communications mode using computers or suddenly finds out that there is still a lot of room for experimenting at the millimeter wavelengths...
Si amigos, yes my friends, oui mes amis in Canada and the French speaking Caribbean that listen to this program, radio is simply fascinating...
Take for example this weekend's CQ Radio Amateur magazine WPX CW contest, when thousands of amateur radio stations around the world are on the air to try to work as many new prefixes as possible...According to my own on the air on 40 meters, so far the WPX contest this weekend was quite a challenge to the participants due to the extremely low solar activity that has prevailed for the past week.
From the very beginning on Satuday at 00 UTC when the contest started, that was Friday evening for us here in the Americas, it was clear that the bands above 14 megaHertz or 20 meters would offer participants very few chances of working many stations, and as a matter of fact, fifteen and ten meters should remain totally closed for F2 mode propagation for most of the time.
So far those really rare goodies picked up on the ham bands, the really hard to work prefixes have shown up on 40 meters, because working on 160 and 80 meters has had to deal with the extremely high QRN that is atmospheric noise levels .
Other maybe not so rare, but nevertheless interesting stations heard during the weekend WPX ham radio CW contest showed up during a short lived opening on 15 meters Saturday morning my local time, when I was giving the finishing touches to the script of this program.
I also heard several South American stations on 10 meters too , proving once again the well known " ham radio contest effect ", that brings in DX stations on an otherwise dead band...
And new prefixes continue to be assigned to amateur stations in countries with a deep rooted tradition in promoting our hobby; that is the case of the prefix 5P7 , that I had never heard before... it took some time to find out that it was a station from Denmark...
And before going over to the next item, once again the world heritage site of the Ecuadorean GALAPAGOS ISLANDS was on the air during an amateur radio contest.
The HC8 prefix would be easy to work for radio amateurs in North, Central and South America as well as the Caribbean during the Sunday morning local time slot.
More radio hobby related information follows as Dxers Unlimited's mid
week edition continues...
.........
This is Radio Havana Cuba , the name of the show is Dxers Unlimited, and here is our next item in today's weekend edition of the program... More about compact antennas for HF and some interesting antenna modeling done, not using computers but in real life, in actual practice, but by building scale models of some antennas... Yes you heard it right a one fifth or one tenth scale model of HF antennas provides a lot of practical information and those scale models have the advantage that they are easy to reproduce and modify.
For example , a working model for the 6 meters or 50 megaHertz meters amateur band of the electromagnetic ground plane antenna system, proved that using a proper ground system, the efficiency of the EMGP vertical antenna will match the radiation efficiency achieved by a full size quarter wave vertical to within a very small percentage.
As a matter of fact, very carefully done field intensity comparative measurements between a full size quarter wave 6 meters band vertical placed at the center of a metal plate that has a diameter of three meters, and an EMGP antenna cut for the same 50.3 megaHertz center frequency proved to be almost exactly the same...
A very interesting finding if you take into consideration that the EMGP antenna's height above the ground plane is just 1/12 of a wavelength, that for the 50 megaHertz or for the 6 meters band it's 24 centimeters or just about nine and a half inches...
Now please compare this antenna height with the 55 inches or about one point fourmeters required by the full size quarter wave or 90 electrical degrees high antenna system for operating at the low end of the six meters ham band.
For six meters band operation of local links , this extremely EMGP low profile antenna will be an excellent choice to be used when extremely strong winds are expected, like when a hurricane is approaching.
An EMGP or electromagnetic ground plane antenna for the 40 metersamateur band, will be only about three and a half meters high above the ground plane, but I must clarify to my listeners that it would not be a very good emergency antenna because it will not have enough high vertical angle radiation , something that is essential for short range Near Vertical Incidence Skywave propagation, as required for short range communications within an affected area.
Nevertheless, modeling the EMGP as a "real life" antenna on 6 meters proved to be a very interesting and rewarding experience, and something that was done in just a few hours of my weekend spare time...
If you don't have enough space where to install a short wave antenna system, don't overlook the possibility of homebrewing an EMGP antenna, that when properly made, will provide reasonable results on the band for which it is cut on transmit, and good receiving on the next lower and higher adjacent bands.
If you want to know more about the EMGP , the Electro Magnetic Ground Plane antenna, send me an e-mail to inforhc@enet.cu , and I will reply with the EMGP Antenna Design Package, with detailed instructions on how to homebrew these antennas for the amateur bands between 80 and 10 meters meters...
......
Si amigos, yes... ASK ARNIE continues to be at the top of your preferences, according to the e-mail messages, letters and actual on the air two way amateur radio contacts... here is ASK ARNIE today... answering a question sent by listeners Rosie in Alberta, Canada,a listener from the USA, Pedro in California and Ian , who tells me that he listens to our 11760 kiloHertz transmitter quite often at his Southern England QTH.
I also received a report and the same question from New Zealand where our 11760 kiloHertz 100 kiloWatts to a 6 dB gain omnidirectioanal antenna deliver a nice signal too, with amazing good quality as amigo Brian tells me in his e-mail.
Well Rosie, Pedro,Ian and Brian want to know more about the recently advertised and much prometed Spiral end loaded antennas that I mentioned here at Dxers Unlimited, and in the case of Ian, who happens to be a very enthusiastic radio amateur operator, he wants me to telll him the difference between the Petlowany and Tak antennas, if there is any difference at all...
Well amigos, the spiral end loaded antennas are really nothing new at all... I remember reading about spiral loaded antennas for the very low frequencies a long time ago, in an article that presented an extensive review of several types of top loaded antennas for operation on very low and extremely low frequencies, using huge top hats made by spiraling a lot of wire .
Then many years ago , some time after reading that article, I went to Cardenas , a city of Matanzas province near Varadero beach. Cardenas has a very nice seaport , where a coastal radio station using the callsign CLC, operated on the now no longer used 600 meters or 500 kiloHertz marine band was installed.
To my surprise the vertical antenna located an an excellent salt marsh swampy area on one side of the bay, had a rather large sized top hat to provide additional loading to the about 70 meters high tower, that was physically too short to resonate efficiently on the 460 to 512 kiloHertz band where it had to operate.
This was just a capacity hat made of spokes and wires, and not a spiral top loading of the tower.
Several months later I had the nice opportunity of talking to the designer of that low frequency band antenna system, and he told me that due to the complexity of the spiral loading configuration, he had opted for the much simpler capacity hat, but he added that a spiral loading system proved to be much more efficient when he was doing "the numbers", that meaning when he was calculating the new antenna for the marine communications site.
I asked him about the size of the projected spiral loading device and he said that even when made with the same diameter as the capacity hat, the spiral was much more efficient and provide much better loading of the structure, something that is essential on those very short antennas for the long waves.
Then, he told me about an experiment that ran under his supervision, when two engineering students that were writing their thesis , made a 10 megaHertz scale model of the 500 kiloHertz antenna system... in other words a one twentieth scale ratio.
The students, the designer said, had much more time to play with the antenna's top loading, and they found out that winding a one quarter wave of wire into a spiral of enough diameter , the antenna's resonant frequency went down dramatically while retaining a rather high radiation efficiency.
But again, he added, the main problem was not of an electrical nature, but one related to the mechanical complexity of keeping the spiral wound loading device in place at the top of a tower when heavy winds are blowing.
In the case of both the Petlowany and the Tak spiral loaded antennas, because they are both dipoles used in a horizontal configuration , keeping the end loading spirals in good shape is not as complicated as with the high towers...So, amigos, now you know a bit more about spiral loading of antennas, and why the Petlowany and the Tak antennas are almost identical !!!
.....
Now ready to copy, as the program is coming to an end, and Arnie Coro's Dxers Unlimited's HF plus low band VHF propagation update and forecast will now go on the air... Solar activity was at extremely low levels, with ZERO sunspot count and the solar flux at 69 units and even lower below...
So, the daytime maximum useable frequency continues to be only barely above 20 megaHertz for short periods, and staying even below 15 megaHertz on some circuits ...
The chances for Sporadic E propagation in our hemisphere is now approaching a maximum for the year, as we enter the month of June...
By the way. there is great expectation for the upcoming ARRL June VHF QSO Party Contest, because if the very low solar activity continues , we may see some really big sporadic E events happening.
Hope to have you all listening to the midweek edition of the program that will be on the air Tuesday and Wednesday UTC days amigos, and don't forget to take a little of your valuable time to send your signal reports, QSL card requests and radio hobby related questions directly to inforhc at enet dot.cu, again, inforhc at enet dot cu or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba.
And new prefixes continue to be assigned to amateur stations in countries with a deep rooted tradition in promoting our hobby; that is the case of the prefix 5P7 , that I had never heard before... it took some time to find out that it was a station from Denmark...
And before going over to the next item, once again the world heritage site of the Ecuadorean GALAPAGOS ISLANDS was on the air during an amateur radio contest.
The HC8 prefix would be easy to work for radio amateurs in North, Central and South America as well as the Caribbean during the Sunday morning local time slot.
More radio hobby related information follows as Dxers Unlimited's mid
week edition continues...
.........
This is Radio Havana Cuba , the name of the show is Dxers Unlimited, and here is our next item in today's weekend edition of the program... More about compact antennas for HF and some interesting antenna modeling done, not using computers but in real life, in actual practice, but by building scale models of some antennas... Yes you heard it right a one fifth or one tenth scale model of HF antennas provides a lot of practical information and those scale models have the advantage that they are easy to reproduce and modify.
For example , a working model for the 6 meters or 50 megaHertz meters amateur band of the electromagnetic ground plane antenna system, proved that using a proper ground system, the efficiency of the EMGP vertical antenna will match the radiation efficiency achieved by a full size quarter wave vertical to within a very small percentage.
As a matter of fact, very carefully done field intensity comparative measurements between a full size quarter wave 6 meters band vertical placed at the center of a metal plate that has a diameter of three meters, and an EMGP antenna cut for the same 50.3 megaHertz center frequency proved to be almost exactly the same...
A very interesting finding if you take into consideration that the EMGP antenna's height above the ground plane is just 1/12 of a wavelength, that for the 50 megaHertz or for the 6 meters band it's 24 centimeters or just about nine and a half inches...
Now please compare this antenna height with the 55 inches or about one point fourmeters required by the full size quarter wave or 90 electrical degrees high antenna system for operating at the low end of the six meters ham band.
For six meters band operation of local links , this extremely EMGP low profile antenna will be an excellent choice to be used when extremely strong winds are expected, like when a hurricane is approaching.
An EMGP or electromagnetic ground plane antenna for the 40 metersamateur band, will be only about three and a half meters high above the ground plane, but I must clarify to my listeners that it would not be a very good emergency antenna because it will not have enough high vertical angle radiation , something that is essential for short range Near Vertical Incidence Skywave propagation, as required for short range communications within an affected area.
Nevertheless, modeling the EMGP as a "real life" antenna on 6 meters proved to be a very interesting and rewarding experience, and something that was done in just a few hours of my weekend spare time...
If you don't have enough space where to install a short wave antenna system, don't overlook the possibility of homebrewing an EMGP antenna, that when properly made, will provide reasonable results on the band for which it is cut on transmit, and good receiving on the next lower and higher adjacent bands.
If you want to know more about the EMGP , the Electro Magnetic Ground Plane antenna, send me an e-mail to inforhc@enet.cu , and I will reply with the EMGP Antenna Design Package, with detailed instructions on how to homebrew these antennas for the amateur bands between 80 and 10 meters meters...
......
Si amigos, yes... ASK ARNIE continues to be at the top of your preferences, according to the e-mail messages, letters and actual on the air two way amateur radio contacts... here is ASK ARNIE today... answering a question sent by listeners Rosie in Alberta, Canada,a listener from the USA, Pedro in California and Ian , who tells me that he listens to our 11760 kiloHertz transmitter quite often at his Southern England QTH.
I also received a report and the same question from New Zealand where our 11760 kiloHertz 100 kiloWatts to a 6 dB gain omnidirectioanal antenna deliver a nice signal too, with amazing good quality as amigo Brian tells me in his e-mail.
Well Rosie, Pedro,Ian and Brian want to know more about the recently advertised and much prometed Spiral end loaded antennas that I mentioned here at Dxers Unlimited, and in the case of Ian, who happens to be a very enthusiastic radio amateur operator, he wants me to telll him the difference between the Petlowany and Tak antennas, if there is any difference at all...
Well amigos, the spiral end loaded antennas are really nothing new at all... I remember reading about spiral loaded antennas for the very low frequencies a long time ago, in an article that presented an extensive review of several types of top loaded antennas for operation on very low and extremely low frequencies, using huge top hats made by spiraling a lot of wire .
Then many years ago , some time after reading that article, I went to Cardenas , a city of Matanzas province near Varadero beach. Cardenas has a very nice seaport , where a coastal radio station using the callsign CLC, operated on the now no longer used 600 meters or 500 kiloHertz marine band was installed.
To my surprise the vertical antenna located an an excellent salt marsh swampy area on one side of the bay, had a rather large sized top hat to provide additional loading to the about 70 meters high tower, that was physically too short to resonate efficiently on the 460 to 512 kiloHertz band where it had to operate.
This was just a capacity hat made of spokes and wires, and not a spiral top loading of the tower.
Several months later I had the nice opportunity of talking to the designer of that low frequency band antenna system, and he told me that due to the complexity of the spiral loading configuration, he had opted for the much simpler capacity hat, but he added that a spiral loading system proved to be much more efficient when he was doing "the numbers", that meaning when he was calculating the new antenna for the marine communications site.
I asked him about the size of the projected spiral loading device and he said that even when made with the same diameter as the capacity hat, the spiral was much more efficient and provide much better loading of the structure, something that is essential on those very short antennas for the long waves.
Then, he told me about an experiment that ran under his supervision, when two engineering students that were writing their thesis , made a 10 megaHertz scale model of the 500 kiloHertz antenna system... in other words a one twentieth scale ratio.
The students, the designer said, had much more time to play with the antenna's top loading, and they found out that winding a one quarter wave of wire into a spiral of enough diameter , the antenna's resonant frequency went down dramatically while retaining a rather high radiation efficiency.
But again, he added, the main problem was not of an electrical nature, but one related to the mechanical complexity of keeping the spiral wound loading device in place at the top of a tower when heavy winds are blowing.
In the case of both the Petlowany and the Tak spiral loaded antennas, because they are both dipoles used in a horizontal configuration , keeping the end loading spirals in good shape is not as complicated as with the high towers...So, amigos, now you know a bit more about spiral loading of antennas, and why the Petlowany and the Tak antennas are almost identical !!!
.....
Now ready to copy, as the program is coming to an end, and Arnie Coro's Dxers Unlimited's HF plus low band VHF propagation update and forecast will now go on the air... Solar activity was at extremely low levels, with ZERO sunspot count and the solar flux at 69 units and even lower below...
So, the daytime maximum useable frequency continues to be only barely above 20 megaHertz for short periods, and staying even below 15 megaHertz on some circuits ...
The chances for Sporadic E propagation in our hemisphere is now approaching a maximum for the year, as we enter the month of June...
By the way. there is great expectation for the upcoming ARRL June VHF QSO Party Contest, because if the very low solar activity continues , we may see some really big sporadic E events happening.
Hope to have you all listening to the midweek edition of the program that will be on the air Tuesday and Wednesday UTC days amigos, and don't forget to take a little of your valuable time to send your signal reports, QSL card requests and radio hobby related questions directly to inforhc at enet dot.cu, again, inforhc at enet dot cu or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba.