Radio Havana Cuba Dxers Unlimited Dxers Unlimited's Sunday July By Arnie Coro radio amateur CO2KK

Transcription

1 Radio Havana Cuba Dxers Unlimited Dxers Unlimited's Sunday July By Arnie Coro radio amateur CO2KK Hello amigos, welcome to this special edition of Dxers Unlimited, recorded two days before it went the air, because at the time you are listening I am going to be enjoying my summer holidays. Yes, I am your host Arnie Coro, radio amateur CO2KK, and as always it is my great pleasure to share with you about ten minutes of on the air, and also on the world wide web time... Here is now item one of this special edition of Dxers Unlimited. A ham radio operator, Gustav, is one of the many who listens to this program using a homebrew transistorized regenerative receiver. Gus wrote an telling me that his three transistors battery operated radio with plug in coils is

2 capable of tuning from the bottom of the broadcast band to the low end of the amateurs ten meters band. Gus uses an inverted L antenna for listening to the lower bands, and a nest of three dipoles cut for the 20, 15 and 10 meters ham bands. With the inverted L he uses a set of three elevated radials, and he feeds the nest of dipoles via a one to one balun and 75 ohms TV type coaxial cable, that is cheaper than the 50 ohms type. Gus enjoys using the battery powered home brew receiver for picking up DX on his favorite amateur band, that happens to be the 40 meters or seven megahertz band. He has made the coils to provide bandspread tuning from seven thousand dot zero zero zero up to seven thousand one hundred and twenty five kilohertz, so his radio tunes with excellent bandspread to the first one hundred and twenty five kilohertz of the very popular 40 meters band. As I do always, Gus received a fast reply

3 to his request for the new version of a classic two tubes regenerative receiver that he wants to build in order to compare its performance with his version of the HF9 three transistors regenerative that is now his main radio. I also added in my comments about DXing on the 40 meters band... emphasizing that slopers are an excellent choice, especially if you can install three of them using a single mast... I then added that there is even a more complex design, using five slopers, spread at 72 degrees intervals around the compass and using a complex relays switching system that makes the ununsed ones act as reflectors for the one active antenna.in use... This system, although rather complex to install, and requiring several high quality relays, is second only to a 4 elements full size 40 meters band Yagi placed at no less than 40 meters - a full wavelength- above ground. More about my advice about antennas to amigo Gus coming up in a few seconds after a short break for a station ID.

4 I am Arnie Coro in La Habana... cortina This is Radio Havana Cuba and here is more information about one of my favorite wire antennas for Dxing... One important thing about sloping dipoles that is often overlooked is that if they are fed directly with coaxial cable... My way of doing it is to use a one to one balun, so that the coaxial cable outer braid will not radiate and thus distort the vertical radiation pattern of the antenna. One interesting finding that came out of my experiments with half wave dipole slopers, was that adding a three, four or five quarter wave radials acting as a counterpoise, after the end insulator of the low end of the half wave dipole sloper antenna. At CO2KK, my amateur radio station operating on the 20 meters band with a sloper, using the three ground counterpoise elements spreading out provided wonderful

5 DX from Europe when installed with the antenna aiming at 45 degrees azimuth. It was a lot of fun to observe how my sloper gave better signals in Europe a local ham radio a friend of mine's 3 element full size Yagi... My friend said that my antenna was involved in some kind of witchcraft HI HI!!! But no, the witch doctor - yours truly demostrated to him that his full size 3 elements Yagi was just too close to the ground to be able to produce a low wave take off angle, as required for Dxing!!! Later I added another 20 meter sloper ""beaming "" to Japan, and it also worked very well. In my opinion the sloper is the lowest cost, most effective, easy to install and to tune, antenna for the frequency range from 3.5 to 29 megahertz when you want to work DX, and know in advance in which direction do you need to aim in order to add more DX entities. Summarizing... let me now ask a question... Is your 40 meters band sloper fed by directly connecting the center

6 of the coax to one side of the dipole and the braid to the other? If you are feeding it that way... it would not behave as a ""real sloper"", because the outer layer of the coaxial cable braid will radiate, contributing significantly to distorting your antenna's radiation pattern in the vertical plane!!! Sure amigos, your radio hobby related questions and comments, as well as new ideas to make Dxers Unlimited a more attractive program for the world's radio hobby enthusiasts are much appreciated, and do receive a fast and comprehensive reply... Now at the request of several Dxers Unlimited listener's that are also amateur radio operators, here is our next radio hobby related item... More about the Super Islander version 5 solid state receiver project is now completed. Among the features of this easy to reproduce design, is that it does not, and I repeat this, it does not use any rare or hard to find electronic components, something

7 that very often is the big stumbling block when someone attempts to homebrew a radio, and then finding out that the designers had included one or more very hard to find or also very expensive parts... Among my main sources of electronic components nowadays, are the compact fluorescent lightbulbs circuits, computer power supplies and motherboards, hard drives, TV sets, Fax machines and in general, obsolete, retired or damaged electronic gadgets that are in their way to the garbage bins... The Super Islander receiver forms part of a more ambitious project... a single band 40 meters ham transceiver that can be built either as a totally solid state radio, or can be part of a hybrid transceiver that uses vacuum tubes for the driver and final amplifier stage... Let me add that the Super Islander is a direct conversion type of receiver, using an extremely simple one transistor mixer, that is coupled to a very well designed front end using a dual tuned bandpass input filter and signal attenuator. The Super Islander's variable frequency oscillator design uses three common bipolar transistors,

8 and although it can not be described as state of the art technology. The prototype Super Islander version 5 and all the following modifications have proven to be very capable of picking up DX on the 40 meters band. Now,, please receive my apologies today, because this program was recorded well in advance of it going on the air, and for that reason, it was not possible to include at the end of the show, one of your favorite sections of the program Arnie Coro's HF plus low band VHF propagation update and forecast... As soon as I am back in town, Dxers Unlimited will again be offering the propagation information that, according to your messages, postcards and letters does help many of you to optimize your listening and for those of you that are amateur radio operators, it also helps to find new nice DX stations too!!! see you at the upcoming edition of Dxers Unlimited and remember that now our weekend program is on the air Sundays and Mondays UTC days just after the top of the hour newscast... send your signal reports and comments to inforhc at enet dot cu or via air

9 mail to Arnie Coro, Radio Havana Cuba, Havana Cuba