Radio Habana Cuba
Dxers Unlimited
Dxers Unlimited's midweek edition for Nov 13-14 2007 By Arnie Coro radio amateur CO2KK
Hi amigos radioaficionados... from Havana, this is the midweek edition of your favorite radio hobby program the one and only featuring the most up to date HF plus low band VHF propagation updates and forecasts... I am Arnie Coro, radio amateur CO2KK, your host here at Dxers Unlimited, a show devoted to the promotion and development of our wonderful hobby, yours and mine ... RADIO... Item one: Scientists now are voicing their different opinions about the forecasts that upcoming solar cycle 24 will be the one reaching the lowest peak number of sunspots in many, many years... as a matter of fact, the peak mean sunspot number expected, and this, I emphasize is according to one school of thought is said to be barely 75 mean sunspots, something that will turn the frequency range above 20 megaHertz into the equivalent of a VHF band for years to come!!!... So, if we believe this forecast it’s about time to prepare for much lower solar activity to last for a loooong time amigos!!! The other group of solar scientists says that cycle 24 may be very active, and even so active as to reach an average sunspot number that will get close to the record breaking cycle 19, the one that passed the 200 sunspot number mark Item two: Uncoordinated DRM, digital radio mondiale broadcasts are continuing to harm reception of regular , standard, AM double side band plus full carrier, A3 mode international shortwave broadcasts, inside the bands assigned by the ITU for that service...The reason has nothing to do with DRM broadcast technology at all, the main causes of this problem can be traced to not coordinating properly so as to make DRM transmissions compatible with standard AM and also because of poorly adjusted transmitters used for some DRM broadcasts that are to be blamed according to experts Several highly qualified radio broadcasting engineers think that there is no room for DRM on the present high frequency international broadcast bands due to what they describe as an unforethought incompatibility between AM and DRM..., in other words, they are appealing creating special frequency spectrum allocations for DRM transmissions, so that they will not interfere with the traditional technology used by short wave broadcasters since the very early days or radio. This criteria started when several chief engineers at stations suffering from interference from DRM transmissions asked for those DRM broadcasts to be placed on a separate segment of the assigned bands , effectively giving them a sub-band, something that in my opinion may prove to be a very wise move. In the meantime DRM, digital radio mondiale continues to be heard by only a very small number of listeners worldwide, as low cost, practical receivers for DRM are still practically non existent for the public to buy...
Once again your valuable comments about DRM broadcasts are invited amigos, just take a little time to send me your opinion about DRM to arnie@rhc.cu, or via air mail, send a postcard to Arnie Coro, Radio Havana Cuba, and Havana, Cuba...
Now stay tuned, for more radio hobby related information coming to you from Havana... I'll be back in a moment, after a short break...
......
More nice worldwide radio amateur contests will take place during upcoming weekends... In the case of these contests, what the winners will achieve is working the greatest number of stations, and each new country worked are the multipliers of the contest...!!! Operating during amateur radio contests is always a challenge and is one of the more than 80 ways that you and I may enjoy this wonderful hobby...
Item four: More ham radio software available free of charge... at absolutely no cost, thanks to ham operators that make their programs freely available for the benefit of radio amateurs worldwide... among them the excellent propagation forecasting and now casting program by W6EL, by Sheldon C. Shallon, who wrote it in 2001 and then very kindly made it freeware.... I have used the W6EL propagation forecasting program for the last four years with excellent results, and it compares extremely well with professional, and I must add pretty expensive, software used for precise calculations of short wave radio communications. W6EL's program is very easy to use, and works on many operating systems, but so far I have not seen a LINUX version for it...
In case you don't find W6EL's propagation software on the INTERNET's world wide web for downloading, just send me an e-mail and I will be very happy to send the dot zip file to you, as it is, believe it or not less than half a megabyte in size...There are also some very nice new ham radio software programs written to use the LINUX free and open source operating systems... Among them FLDIGI, that offers several digital communications modes, including the rather new OLIVIA and also the classic RTTY as well as the very popular PSK31.
Send your request to arnie@rhc.cu amigos, and sorry, there is no practical way for me at this moment to send this software by other means than as e-mail attachment amigos...
Item five at this midweek edition of Dxers Unlimited...it's the antenna topics section, an answer to a problem that a Cuban radio amateur was having with his G5RV antenna for the 80 to 10 meter bands... He called
me on one of our local 2 meters band FM repeaters to say that he was having problems with this G5RV antenna..., his rig was oscillating badly when connected to the G5RV multiband antenna, and we soon found out that his antenna tuner's capacitors were arcing between the rotor and stator plates. The problem only happened on 40 meters, and the automatic power shutdown of his recycled Yaesu FT80 will then trip very often in the middle of a QSO... After reviewing the setup at his station, I recomended that he changed the length of the open wire line feeding the G5RV antenna, and also that on 40 meters he used a one to one balanced to unbalanced antenna transformer instead of the four to one ratio he was using... It seems like the impedance transformation done by the open wire line was making the antenna tuner's job a very difficult one...
Once he changed the balun, the problem just vannished. The interesting thing about this problem is that he could work on 80, 20, 15 and 10 meters without any problem, and it was only when he attempted to operate on the 40 meter band that the problem knocked his station off the air...
I thought it would be a good idea to pass this along to Dxers Unlimited's listeners that are also amateur radio operators, because the G5RV compromise wire multiband antenna is very popular , despite the fact that it may act up on some bands as you have just heard. By the way, I have never installed a G5RV, because a fan type wire dipole, fed with 400 ohms open wire length and with its legs between 11 and 25 meters long is a much better antenna by all standards... Just remember to use three wires for each leg of the antenna and separate them at the end by about thirty percent of their length... For example, one of my favorite compact fan dipoles uses 7 meters long legs, separated by about
2.3 meters, providing the user with an antenna that works very nicely from 40 to 10 meters ... A longer version about twice that size provides not only coverage of 80 meters, but also some gain on the higher bands... The separation between the upper and lower wires of the 14 meters long fan dipole is 4.6 meters, but let me add that this is not really critical, as I have used this fan dipoles with less separation between the wires with very nice results... If you want to go by the book, the ideal length for these two antennas are 6.7 meters for the short version designed to work between 7 and 29.7 megaHertz and 13.4 meters for the version designed to work between 3.5 and 29.7 megaHertz.... The use 400 ohm impedance open wire line is essential to obtain the benefits of these antenna designs, and the actual length of the open wire line should be a bit more of a quarter wavelength at the lowest operating frequency , taking into consideration the velocity factor of the line, in this case about 0.92... By the way, as an additional bonus, the fan dipoles are really broadband antennas, so they are excellent for monitoring purposes and listening to international short wave broadcasts from 6 all the way up to 26 megaHertz, that is from the 49 to the 11 meters bands..
.....
This is Radio Havana Cuba, the name of the show is Dxers Unlimited, I am Arnie Coro, your host here at this twice weekly program devoted to all the different aspects of the radio hobby, from home radioastronomy to Dxing on the AM broadcast band with a crystal set... from working an amateur radio contest to wiring up your own low power QRP transmitter and using it on the air, accepting the challenge of operating with powers less than 5 Watts into the antenna... Yes my friends, radio is never boring, because you can always learn about a new and fascinating way of enjoying it ...Even at the solar minimum some very special propagation conditions dos how up... At CO2KK my ham radio station I am picking up amateurs from South America on the 10 meters band practically every day, despite the extremely low solar activity and those are amazing signals considering the low powers used... Even with a simple half wave wire dipole just 3 meters above my rooftop, I have made excellent two way contacts on the 28 to 29.7 megahertz band,10 meters, with stations in Argentina, Uruguay, Brazil, Paraguay and Chile.
...
You have QUESTIONS, and Arnie tries to answer them as soon as they arrive here to my e-mail box arnie@rhc.cu, or at the postal address Arnie Coro, Radio Havana Cuba, Havana, Cuba... Today's question came from Germany, where many listeners pick up our English language web cast that goes on the air from 05 to 07 hours UTC... Amigo Dieter from Cologne asks if it is possible to use a retired C band satellite dish antenna for amateur radio work... Answer, sure amigo, you can turn that parabolic reflector into a useful antenna for both terrestrial and space Dxing depending on the type of mount that you decide to use. For terrestrial applications the typical 3 meters diameter C band retired satellite antenna will make an excellent reflector for amateur radio bands in the range between 70 centimeters and 5 centimeters... but as I just said, it will require a rather expensive mounting system so that the dish can be installed at enough height above ground and also rotated in azimuth... Some amateurs that live at hilltop or mountaintop locations have used the C band antennas at ground level, and aiming them by hand with excellent results, but not everyone has the privilege of enjoying such excellent " made for VHF, UHF and Microwaves "
locations...By the way, once I placed a two meters band half wave dipole at the focus of a 3 meters diameter parabolic reflectors that was retired from satellite receive only duty and found out that it showed gain similar to a three element Yagi that was installed at the same height !!!
Now our exclusive and not copyrighted HF plus low band VHF propagation forecast... Solar activity is still at extremely low levels, zero sunspots one day after the other, and now expect a geomagnetic disturbance to make HF propagation at high latitudes still worse. The daily solar flux barely reaching 70 units.
See you all at the upcoming weekend edition of the program amigos, and don't forget to take a little time now to drop me an e-mail with a signal report and your comments about today's Dxers Unlimited, send mail to arnie@rhc.cu !!! Or Send an AIR MAIL Postcard to Arnie Coro, Radio Havana Cuba, Havana Cuba.
