RADIO HABANA CUBA
DXERS UNLIMITED
WEEKEND EDITION
SATURDAY, JANUARY 5, 2002
By Arnie Coro CO2KKSend your comments, questions and ideas to: arnie@radiohc.org
Hi, amigos radioaficionados! Welcome to the weekend edition of your favorite listener-oriented radio hobby program, I am Arnie Coro, radio amateur CO2KK, your friend in Havana and host of this twice weekly program, entirely, absolutely devoted to our wonderful hobby, the one and only you can enjoy in more than 64 different ways... Because yes, I did found yet another way of enjoying the hobby, by collecting radio publications of all types....
Now here is item one: Although this last one was not Earth directed, it did produce a very interesting display... Yes, I am talking about the last solar flare that scientists recorded on Friday... Solar activity continues in high gear and accordingly we are witnessing an unprecented period of very high maximum useable frequencies that amateur radio operators on the 6 meter band have used to add lots of new countries to their logs...
Item two: The most popular question asked by Dxers Unlimited's listeners since the very early days of the program is: "Arnie, I have just enough space for a single outdoor antenna....please advise on the best possible antenna for short wave," and yes, we have always offered three options -- the wide band TTFD, or tilted terminated folded dipole, the wide band fan dipole, and the narrow band but ultra compact magnetic loop antenna.... with a fourth option following closely in the form of an inverted L antenna working via an antenna tuner unit!!!!
Item three: Had a nice time Saturday morning here working on the 12 meter amateur band to Europe... The 12 meters band is one of the narrow segments of short wave spectrum assigned to amateur radio in 1979 during the International Telecommunications Union World Administrative Radio Conference held that year... It is only 100 kiloHertz wide, and starts on 24.890 kiloHertz ending up on 24.990 kiloHertz. With a simple wire antenna, and running anywhere from 20 to 100 watts you can work the world on phone using the 12 meters band, amigos!!!!
Stay tuned for more radio hobby related items, coming up in a few seconds.
This is Radio Havana Cuba, the name of the show is Dxers Unlimited, and yes, we do QSL and also answer your radio hobby related questions -- just send your e-mail to arnie@radiohc.org and Via Air Mail (a postcard will be fine) send it to Arnie Coro, Radio Havana Cuba, Havana, Cuba....
Now, here is item four, You have questions and Arnie answers them.... Question: Arnie, how many wires I must use to make a true fan conical dipole? The question was sent in by a listener in Canada, who is going to build a fan conical dipole antenna. He wants to know how many wires are needed to make the conical fan behave as such, and not as a single wire antenna...
Well amigo, you should use at least five wires, separated to form the cone, and making the ratio of the cone length to diameter of no more than 5 to 1... In other words, a true conical fan dipole must really be defined geometrically in a proper way, in order to make it behave electrically as a broadband structure... although you can certainly build a fan dipole that may have a minimum of three wires and all of them placed on a single plane. This non-ideal system will work, providing a certain degree of extended bandwidth, and impedance variations that can be easily handled by a simple antenna tuner...
BUT, it you really want a conical fan dipole, then you must design a true circular cone system, defining its limits by a minimum number of five wires, while ten wires would be a much better option. Of course you can also make yourself a fan conical monopole, and use it as a broadband vertical antenna, but this other antenna will require the installation of a ground system of no less than sixteen quarter-wave radials at the lowest operating frequency... The conical fan dipole, with its legs extending to about 10 meters on each side of the center insulator, and with a length-to-diameter ratio of 3.33, is not only a very nice-looking antenna, but it also performs very well for both receiving and transmitting in the frequency range from 6 megaHertz all the way up to 24 megaHertz, a very nice four-to-one ratio.... The antenna should be fed using a balanced transmission line of an impedance as close as possible as 400 ohms, and the line should go to either a balanced antenna tuner, or connected via a balun to a standard coaxial line tuner... The conical fan dipole is an excellent broadband antenna, that outperforms the TTFD or Tilted terminated folded dipole, but that is somewhat more difficult to install and requires a lot more wire to make!!!!
You are listening to Radio Havana Cuba, this is the Weekend edition of Dxers Unlimited. and amigos I keep receiving very nice e-mail messages, postcards, letters and FAX messages encouraging me to keep up the good work during this year 2002. Yes amigos, you can all be sure, that as always, I'll do my best to make Dxers Unlimited your favorite technical radio hobby program, without forgetting operating tips and homebrewing of radio equipment, and our ever-popular Arnie Coro's Dxers Unlimiteds HF plus 6 meters propagation updates and forecasts....
Now here is item five... more about simple radio receivers that you can homebrew using recycled components.... Sunday afternoon several newcomers to our hobby will be building their first VFO variable frequency oscillators... The VFOs are phase two of a project that started by building a 13.8 volts DC regulated power supply, that all four of them are now working perfectly... The VFO will be followed by a single band receiver module, so that they can start listening to the 40 meter amateur band as soon as those four radios are finished.... These are all solid state radios, powered from the standard AC power line, and capable of providing room-filling volume. The parts to build them are not critical at all, and choosing the 40 meter band was a very good decision, as that amateur band is open during the day for short range contacts, but as soon as the sun begins to set, it opens up for a lot of DX.
The receivers have a well-designed input attenuator and bandpass filter, and although they are of the so-called direct coversion or homodyne type, they perform very well for receiving both CW Morse Code Signals and Single Side Band voice. This project will eventually end up in an amateur band transceiver, making use of all the building blocks that the newcomer wires up during the different stages... For example, the direct conversion receiver is used later as the tail end of a classic single conversion superheterodyne receiver, the VFO is simply moved from the 7 megaHertz band down to 5 megaHertz so that it will provide the appropriate injection frequency to produce a 2 megaHertz intermediate frequency...
Once the Phase two receiver is finished, its proud owner can add an audio filter for both CW and SSB, ending up with a nice, compact, and sensitive radio. Phase three requires the newbies to pass their amateur radio license test, so that thye can build a simple CW and Double Side Band 10 to 20 watt transmitter that matches with the receiver.
One of these solid state beginner's stations will provide many hours of radio operating enjoyment on the 40 meter band, and several of them have contacted more than 50 countries on both CW and Sideband using a simple half-wave 40 meter dipole antenna. A lot of the parts for the project can be found by recycling electronic components from old TV sets, VCRs, FAX machines, computers and other electronic gear, keeping the cost of the complete project rather low!!!
If you want to know more about this step-by-step project to build your own power supply, receiver and transmitter, just drop me an e-mail to arnie@radiohc.org and I will be very happy to send you a complete description of this beginner's station which, by the way, can also receive at least one international short wave broadcast band!!!!
Yes amigos, homebrewing your own radio gear is a lot of fun, and among the equipment that you can build all by yourself, maybe with a little help from an experienced amateur radio enthusiast, the antenna tuner is my favorite project.
A very simple yet effective tuner needs but a few parts, is easy to wire up, and will enhance your reception tremendously, even when you are using a very simple antenna system... Two variable capacitors, a hand wound coil on a length of PVC pipe, a multi-position wafer switch, and your tuner is ready, needing only connectors and cable to install it between your receiver and your antenna...
This homebrew tuner will dramatically improve the performance of the typical small portable short wave radio, that's why I always tell radio hobbyists to build at least one of them!!!! Yes, homebrew tuners are a lot cheaper, and they do work very well when properly built!!!
Want to build your own antenna tuner? Then just drop me an e-mail and I will send you the circuit diagram of a very nice tuner that can be switched into several different configurations to obtain optimum results... send your e-mail to arnie@radiohc.org or an AIR MAIL postcard to Arnie Coro, Radio Havana Cuba, Havana, Cuba.
And now amigos, as always at the end of the show, here is Arnie Coro's HF plus 6 meters propagation update and forecast: Very high maximum useable frequencies during the daytime hours continue to provide 6 meter band operators with unique two-way contacts on the MAGIC BAND!!!! And I expect excellent DX conditions on 6 meters to continue for the next ten days!!! Meanwhile propagation on the 10 and 12 meter bands, and on the 13 meter international short wave broadcast band continues to be excellent... I have worked many 10 meter band Single Side Band voice stations during the past several days while running just 5 watts to a half wave dipole antenna...
Solar flux has stayed above 200 units for many, many days, providing the ionosphere with lots of free electrons to make radio waves travel fantastic distances!!!! So here is your friend Arnie Coro's advice: Monitor the higher frequencies, in the range from 20 to 50.5 megaHertz for the best DX opportunities of this winter!!!
Prepared Jan-05-2002; received by NY Transfer News Jan-08-2002, 06:00 EST
Arnie Coro CO2KK
Havana, Cuba
January 5, 2002Postal address:
Arnie Coro, "Dxers Unlimited"
Radio Havana Cuba, Havana, CUBA
e-mail: arnie@radiohc.org
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