Tuesday, July 24, 2007

DXers Unlimited edition July 21-22


By Arnie Coro - CO2KK

Hi amigos radioaficionados... I am Arnie Coro in Havana, and its my pleasure to share with you about seventeen minutes of on the air and on the web time talking about our favorite hobby, yours and mine...

RADIO... Item One: More days with an absolutely spotless solar disk are expected soon... not a single sunspot will be seen during a several days period according to solar forecasters, something that tells us a lot about the way solar cycle 23 is decaying...

Item Two: Everybody knows that whenever there is a massive emergency, cellphones simply stop working, or in the best possible scenario, it is very difficult to communicate using them. BUT, simple , relatively low cost amateur radio two meters and seventy centimeter bands continue to work nicely ,providing reliable communications links that are not dependent of the number of users of the system, like cellphones are...

That's why amateur radio continues to be regarded as a most reliable way of communicating during emergencies, something that here in Cuba we have found out when several powerful hurricanes , Michelle, Isidore, Lili, Charley and Dennis struck our archipelago !!! By the way, a low cost handheld FM two meter band transceiver and a very simple antenna system is all you will need to stay in touch via a repeater, even under the worst weather conditions !!!

Item Three: More about the Micro Vert antenna, and how it compared to a one meter diameter magnetic loop...Some experts are telling now that what is actually radiating in the case of the MicroVert antenna is a section of the outer braid of the coaxial cable feedline ! And at the end of the program, our exclusive and not copyrighted HF propagation update and forecast... Stay tuned... in just a few seconds more radio know-how for your enjoyment follows... I am Arnie Coro in Havana...

This is Radio Havana Cuba, the name of the show is Dxers Unlimited, and for first time listener's information this is a twice weekly program devoted to the promotion and development of the wonderful hobby of radio, one you can start enjoying without investing a single cent... just by using your already existing radios to catch far away stations, in other words to enjoy DXING ... !!! More about the Micro Vert ultra compact single band antenna...All I can say is that it seems to work, after all... For the past several days I have experimented quite a bit with the 40 meters band version of the Micro Vert, with my new PSK31 digital communications mode capability at CO2KK, and among the findings that I wish to share with you is that it makes a nice receiving antenna for both the 49 ,41, 31 and 25 meters international shortwave broadcast bands... and that , of course is a bonus... as the Micro Vert antenna is usually thought as a single band system for amateur radio work, in other words a rather narrow band antenna... But, I found this quite by chance, when connecting the Micro Vert's 50 ohm coaxial cable downlead to an amateur band's transceiver that also has extended coverage of the HF spectrum. The transceiver was tuned to Radio Havana Cuba's 9550 kiloHertz frequency, and to my surprise, the station came in loud and clear with the Micro Vert... The Micro Vert cut for the 40 meters ham band , used as a receiving antenna delivered excellent reception on 41 meters , as one could expect, but it did also provide quite good reception of the 31 ,25 and 22 meters bands broadcasters...

Later I ran another detailed comparative test on the 40 meters band while running 20 Watts of PSK31 mode , using the Micro Vert and a One Meter Diameter Magnetic Loop , so that both antenna could be switched very fast at the receiver's input. Results showed that , depending on the distance from the transmitting station, one could receive always equal or better signals on the Micro Vert... without having to retune every few kiloHertz, as you have to do with the Magnetic Loop...

The Micro Vert is a rather practical and compact single band solution for radio amateurs that otherwise can't operate on the HF bands due to lack of space for a standard size antenna system. So far I have built three of these antennas, one for 40 meters, another one for 30 meters and still another one for the most popular DX ham band of them all: 20 meters. In all three cases it was not really difficult to tune up the antennas, and results show, that even under recent poor propagation conditions, the Micro Verts have allowed me to carry on nice two way contacts....

The worst signal report given for the Micro Vert on 20 meters by a station about 1500 miles away from Havana, was about 2 S units below my very efficient quarter wave ground plane ... While the signal from the ground plane was reported as S9...the signal from the Micro Vert after a fast switch over was S7, an indication that DL7PE, Juergen, the inventor of the Micro Vert was absolutely right when he affirmed that his antenna design could make possible HF operation for many amateur operators that live in the cities...and for that very same reason could not install
antennas for the HF ham bands.
.....
Several days in a row without a single sunspot are now not an uncommon happening !!! Some newcomers to solar observations might have wondered if this was normal or not... but long time observers, like my good friend Angel Gonzalez Coroas , are not shocked by the spotless Sun...

If you want to run your own propagation forecating software, feed the program with a solar flux figure of 70 and you will be hitting ballpark figures during the last 10 days of July !!!

And now, just before going QRT , here is Arnie Coro's Dxers Unlimited's HF propagation update and forecast... CQ magazine's VHF contest is in progress as you are hearing this show, and there are good chances of Sporadic E openings for the participants to enjoy. Solar flux at rock bottom levels near 70 and no sunspots in sight on either side of the Sun...Few chances if any of maximum useable frequencies going above 20 megaHertz, except perhaps via Trans Equatorial Propagation.. Hope to have you all listening to the mid week edition of Dxers Unlimited next Tuesday and Wednesday UTC days amigos !