RADIO HABANA CUBA
DXERS UNLIMITED
MID-WEEK EDITION
TUESDAY, May 21, 2002
By Arnie Coro CO2KKSend your comments, questions and ideas to: arnie@radiohc.org
Hi, amigos radioaficionados worldwide! You are now listening to the mid-week edition of your favorite radio hobby program coming to you from Havana. I am Arnie Coro, radio amateur CO2KK and as always, its my pleasure to share with you about seventeen minutes of air time that will be entirely, absolutely, devoted to our wonderful hobby: RADIO!!!
Here is item one: Digital communications modes continue to win a lot of interest among amateur radio operators around the world.... The so-called SOUND CARD modes continue to evolve with excellent freeware programs that are really user friendly and easy to set up...
Now a second generation of SOUND CARD ready amateur rigs is reaching the marketplace, interesting more hams in digital communications. Of course, to operate the SOUND CARD modes you will need a computer connected to your transceiver, but the computer itself need not be a state of the start GIGAHERTZ SPEED machine... even very modest (by today's standards) computers running at CPU clock speeds as low as 100 megaHertz will operate on the PSK31 keyboard to keyboard mode!!!
So amigos, it's time to start learning more about digital communications modes, and if you are not yet a licensed amateur radio operator, you can still monitor the digital modes with just a good quality communications receiver, a computer with the freeware software of your choice and a simple interconnecting cable between the computer sound card and your radio's audio output. More about digital communications later in today's Dxers Unlimited...
Item two: A lot of feedback from Dxers Unlimited's listeners around the world regarding the Australian-designed two-transistor regenerative FUN RADIO, later modified by yours truly to add a bit more audio output provided by an extra audio transistor... AND YES... it does pick up ham radio stations on both CW and Single Side Band, by making the detector oscillate... in classic regenerative receiver operating fashion... I have tested several field effect transistors in this receiver with excellent results in all cases... More about the AUSTRALIAN REGENERATIVE FUN RADIO later in today's edition of this program.
Item three: Very interesting 6 meter band openings continue to puzzle scientists, as we are now well into the summer season here in the Northern Hemisphere... usually not a good time for F2 long range DX...
Item four: Our popular you have questions and Arnie tries to answer them section of the program... and as always at the end of the show our exclusive and not copyrighted, in the public domain Arnie Coro's Dxers Unlimited's HF plus 6 meters propagation update and forecast. Margarita Delgado is my sound engineer and producer... I am Arnie Coro in Havana, stay tuned...
Item one now in detail: Recent advances in amateur digital communications modes software make possible some really outstanding results with stations that can be set up using older computers equipped with sound cards that are not really the most up to date state of the art hardware. The fact is that hams around the world are getting a hold of Pentium I generation laptops with CPU clock speeds in region between 100 and 233 megaHertz that are now showing up in the second hand markets and using those machines to operate the digital modes very effectively.
I do recommend the laptop approach for one solid reason, the laptop and notebook machines use liquid crystal displays that do not generate radio frequency noise like the typical cathode ray tube computer monitors do... So, by using a laptop or notebook connected to your transceiver or communications receiver, you don't have to deal with the interference generated by the high voltage sweep units of the cathode ray tube monitors... Freeware avaialable for the digital modes is becoming more and more user friendly, and now a new world of amateur radio communications is opening up using sophisticated signal processing technology that can literally recover signals that are way down below the noise level... So amigos, its about time to explore the digital communications modes.... run a search on any of the internet search engines by typing "amateur radio digital communications," or "amateur radio software" and start surfing to learn more about this fascinating way of enjoying our wonderful hobby....
Amigos, you are listening to the mid-week edition of Dxers Unlimited, coming to you from Havana... E-mail me your questions, comments and signal reports to me at arnie@radiohc.org and via air mail, send your signal reports and comments about the program to Arnie Coro, Radio Havana Cuba, Havana, Cuba...
Now item two in detail: The AUSTRALIAN Regenerative FUN RADIO provides really amazing performance when you realize how few parts are needed to build one... It's just a well-designed input tuned circuit and attenuator, the field effect transistor regenerative detector and in the original circuit, just one audio amplifier transistor working into an output transformer that feeds your headphones... In my improved version, I added a second audio transistor and a volume control potentiometer to boost the audio output and be able to control the audio output level. The field effect transistor used in the original circuit is a very common device, and I tested no less than seven other types just to see how the circuit behaved. I even tied the two gates of a dual gate field effect transistor and soldered it into the circuit to see what happened and it work pretty well too...
Then as always, experimenting here with simple circuits, I have just redesigned the detector to use a dual gate field effect transistor that should provide still higher gain and a very smooth regeneration control via the second gate... So, maybe next week I will be able to provide you all with the results of this experiment, in the meantime, start experimenting with the AUSTRALIAN FUN regenerative receiver... send for the circuit diagram.... just drop me an e-mail to arnie@radiohc.org and I'll send you the information about how to build this simple, yet amazingly effective little solid state receiver.
This is Radio Havana Cuba, the name of the show is Dxers Unlimited, and if you are new to shortwave listening amigo....this is the place to stay for a while and learn more about this wonderful hobby.... Now our popular "you have questions and Arnie tries to answer them" section of the program....
Question: Dear Arnie, don't have much space for an external antenna, I just measured that from the top of the single mast that I installed to the far end of my roof it's only a 6 meters, or about 20 feet, horizontal distance.... What's the best short wave antenna that I can fit into that short space avaialable?
Well, amigo Terry from Indiana, USA, let's use geometry to our advantage.... You can tie one end of your antenna to the top of the mast that as you say is 5 meters or about 16 feet high.... and then install a small stub mast of about 2 meters at the end of the roof... You can now install a sloping antenna between the two masts. OK, get the idea? The sloping antenna is going to be a little longer than if you install a horizontal wire...
Now here is what I would do: I would simply build a Tilted Terminated Folded Dipole or TTFD that will fit into that space, leaving just about 20 centimeters at each end for the antenna insulators... You will end up with an antenna of an overall length of, let's use some elementary geometry here... OK, your antenna length should be 6.35 meters, considering that you are leaving 20 centimeters at each end for the insulators. Now amigo Terry, let's test this TTFD's frequency coverage... The standard TTFD length for the lower frequency cut-off is a third of a wavelength.. so, now we multiply 6.35 times 3, and that equals, 19.05 meters....
So your antenna is going to work really well from about 14 megahertz, the 20 meter ham band, all the way up to 30 megaHertz.... and, you will also see that this compact version of the TTFD just 6.35 meters long will still provide nice reception on the 22, 25 and 31 meter bands, and it still outperform your radio's internal telescopic whip many times on the 41 and 49 meter bands...
Try it, believe me amigo Terry, this wideband TTFD's using a terminating resistor in the range from about 800 up to 1000 ohms and with the two wires separated by around 30 centimeters work amazingly well when fed via a 9 to 1 balun, or you can feed the antenna directly with open wire 600 ohm line and connect it to your radio via an antenna tuner of the balanced type. Just to prove my point, I built an antenna just like the one I have just described to you and have used it for general short wave listening and for operating CO2KK my ham radio station on the 20, 17, 15, 12, 10 and 6 meter bands with excellent results...
So amigo Terry, even a very short length NEW TTFD will provide you with much better reception than if you continue to use your radio's telescopic whip, or an indoor wire antenna, or even an external random length of wire... Go for it, the NEW TTFD is an amazing performer even when built in this ultra-compact version... And of course, if one has enough space, then go for the standard 13.4 meters long or 44 feet long NEW TTDF that provides excellent wide band coverage from 6 megaHertz all the way up to 30 megaHertz, with the additional benefit of giving you a nice transmitting antenna for your ham radio station covering from the 40 meter band all the way up to 10 meters with excellent results!
And now, amigos as always at the end of the show, here is Arnie Coro's Dxers Unlimited HF plus 6 meters propagation update and forecast... Solar flux is around 170 units, and there are two solar active regions capable of generating more high intensity solar flares like the X2.1 flare that erupted Monday May 20 at 15.27 UTC... There are chances for long range F2 type openings reaching well past the 50 megaHertz region of the spectrum...
Be on the alert for some 6 meter band openings on Tuesday and Wednesday UTC days... Best bands for daytime short wave listening will continue to be between 17 and 22 megaHertz, while night time reception will be nice between 9 and 18 megahertz.
See you at the weekend edition of the program amigos... next Saturday and Sunday UTC days, and don't forget to send your signal reports and comments to arnie@radiohc.org or via AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba!
Prepared 21-May-2002; received by NY Transfer News 22-May-2002, 21:00 EST
Arnie Coro CO2KK
Havana, Cuba
May 21, 2002Postal address:
Arnie Coro, "Dxers Unlimited"
Radio Havana Cuba, Havana, CUBA
e-mail: arnie@radiohc.org
To Arnie Coro's Dxers Unlimited
Back to NY Transfer's RHC main page