Dxers Unlimited

Midweek edition for: 6-7 December 2005

By Arnie Coro CO2KK

Hi amigos radioaficionados worlwide, I am Arnie Coro, radio amateur CO2KK,your amigo in Havana, and this is the mid week edition of Dxers Unlimited, reaching you under what could best be described as excellent HF propagation conditions, as the effects of a high speed solar wind and active solar sunspot region 826 faded away... The daytime 3000 kilometers F2 layer single hop propagation map shows areas where signals on the amateur 10 meters band may be heard during the next two to three days. As the winter solstice day approaches, we may see more sporadic E skip openings that make possible single hop propagation of signals in the frequency range between 20 and 150 megaHertz, but more typically only up to around 70 megaHertz or so... The winter sporadic E season has already started, and I have picked up several TV channel 2 stations from Central America , the USA and Mexico...Item two: CM2IRG, my good friend Reynaldo is a newcomer to the amateur radio hobby with his own home station.

During several years he operated from our Plaza Radio Club station, using his CL2BMC callsign... but now, thanks to a radio equipment recycling program , Rey has his own 2 meters band station. His radio , a Kenwood ex mobile unit was used by a Cuban taxi cab company that has now upgraded to more modern technology.. The old radios from the taxicabs went to the National Federation of Radio Amateurs as a donation, and they were distributed to the local radio clubs to those who didn't have their own home ham stations.

Rey's rig is running 20 Watt output of a nominal 25 Watts, as I reduced the power of the final stage a bit to reduce heat dissipation... We also worked on his antenna system, testing it for standing wave ratio and antenna pattern.

The two element vertically polarized Yagi is beaming at a repeater located some 50 miles west of Havana , at the Sierra del Rosario mountain range TV station site.

The 4 dB gain antenna is working nicely, and it has also coverage on the back of the beam to the three downtown Havana two meters band FM repeaters and to the local packet radio BBS.... By the way, the antenna that I designed for CM2IRG is very easy to homebrew, and required no adjustment whatsoever... we just checked it with a professional standing wave ratio meter and found out that the highest SWR was at the high end of our band that spans from 144 to 146 megaHertz. As Rey will operate his station mostly on the repeater segment, between 144.510 and 145.000, we decided to leave the antenna with the present element dimensions, and then proceed to cut the driven element a little bit to move the frequency response curve up ...
something we plan to do soon. The reason we didn't do it on Sunday is that the SWR tests were done during a visit that Roxana my wife, little Claudia our baby daughter and yours truly made to Reynaldo's and Ramil's home... Amateur radio is a hobby that develops ties between people and long time friendships.. by the way Ramil, Reynaldo's wife is also an amateur radio operator and she shares the same station with her husband...
More radio hobby related information coming up in a few seconds as Dxers Unlimited's mid week edition continues after a short break..................................

This is Radio Havana Cuba, the name of the program is Dxers Unlimited, and if you are a first time listener,
please take a little time to tell me and Dxers Unlimited's fans around the world more about how you enjoy the radio hobby... I recently received an e-mail from an old timer that is very much involved in antenna modelling, but not only using a powerful desktop computer and several sophisticated software packages... Amigo Otto also builds beautiful fully functioning scale models of his antenna designs...and he told me in his e-mail that he has now three ground plane systems to test his antennas... One is a copper plate about a 6 millimeters thick that he carefully has cut to a circular form of exactly one and a quarter meters diamter.

The second ground plane system is also made of copper plate but is a bit less than half the size, with a
diameter of 50 centimeters, and his third ground plane system designed to test antennas is using up quite some space of his backyard as it is 6 meters in diameter and formed by 120 equally spaced copper wires around a center copper plate. This large sized ground plane is located exactly one meter above the ground,
so Otto can actually crawl below the ground plane and place test instruments right at the base of the antenna... In a very funny way amigo Otto told me that he should had made the elevated ground plane or counterpoise higher, so that it would be easier to work below it...Now, I am sure that many of you will like to know what
amigo Otto, is doing with his three ground plane systems.

Otto tests antenna designs using several sophisticated measuring instruments, but also uses the experimental antennas to actually operate his amateur radio station. Among the valuable information he has provided is a complete set of measurements of a low profile antenna that he modelled after reading what Otto described as a very interesting paper about an antenna system made of four inverted L wires connected in pararell. He was surprised with the results obtained with this antenna on the six meters band , both with local stations and when the band opened up for DX during the past summer, he was able to work quite a few stations with this unique antenna that is only 30 centimeters high above the copper plate ground plane.

A full size six meters band quarter wave vertical antenna is a bit less than one and a half meters high...so this
low profile system is 5 times lower in height than the quarter wave... Amigo Otto is continuing to test several
variations of the so called ElectroMagnetic Ground Plane or EMGP antenna... but so far the best results obtained continue to be with the four wires system... Scaling up this antenna for the most popular HF amateur band, the queen of DX, 20 meters or 14 megaHertz, may prove to be a worthwhile effort for many radio amateurs that do have access to rooftops of apartment buildings but that are restricted by building regulations from installing antennas that may be actually higher than the lightning rods.

As I thought that this design was something really attractive for many Dxers Unlimited listeners that are also radio amateurs, I asked Otto to model it with all of his sophisticated computer antenna modeling programs... and he came out with an antenna system that is actually less than one meter high above the ground plane... Just to give me an idea of how a simplified single element version of this antenna might work, I have built one for twenty meters using an eight wire counterpoise, and so far results are quite interesting ... Next step will be to place it side by side with a full size quarter wave vertical antenna with an identical eight wire counterpoise, and to connect both antennas to a switch, so that I can change instantly between one or the other right in the middle of a two way contact, or when receiving a weak station... That's the kind of antenna performance test that in my opinion is THE WAY TO GO when you are looking for higher performance under restricted space conditions... Antenna modelling with computers and actual antenna modelling with real life wires and elements is one of the more than 77 ways that you and I may enjoy more our wonderful hobby... radio !!! By the way there are lots of nice computer software programs for antenna modelling that can be downloaded freely from several Internet websites... Run a search on any of the popular Internet search engines with the words
antenna modelling software linked by a plus sign between words and be prepared to start downloading by the most popular ones like MMANA, a Japanese freeware that work's great and the different versions of the NEC , Numerical Electrical Code software ...........................

Yes, it's true , scientists are able to monitor what's happening on the farside of the Sun... in other words , using
sophisticated Heliosysmic techniques, solar researchers can know when medium and large sunspots are there... Right at this moment heliosysmic analysis show the presence of at least a large sized sunspot on the farside of the Sun, and this one may be one that's not new at all.... a sunspot still active after rotating away from Earth view... And talking about sunspots the daily optical sunspot count is around 85 and now moving down... something that in my opinion will enhance the chances of sporadic E layer events during the next several
days... QSL on the air... Si QSL on the air, to all Dxers Unlimited's listeners that have sent e-mail messages to arnie@rhc.cu, or postcards and letters VIA AIR MAIL to Arnie Coro, Dxers Unlimited , Radio Havana Cuba, Havana, Cuba, YES amigos there is a que, a waiting line now for answering your radio hobby related questions , as there are no less than 53 questions to be answered both on the air and also via direct e-mail
or AIR MAIL letters to listeners that have asked them...Among the most popular questions at this particular moment are those related to how the HF bands will behave during the really low ebb of the solar cycle....so, I will try to answer them during the weekend edition of Dxers Unlimited. Again, and just in case you tuned in late... present HF propagation conditions are pretty good, solar activity is low but enough to provide us with a rather nice F2 layer daytime propagation that may peak up to frequencies as high as 30 megaHertz on the
better propagation paths.

06-Dec-2005 at 1208 UTC SFI = 92 A = 3 K = 2

Conditions during the last 24 hours No space weather storms were observed for the past 24 hours.
Forecast for the next 24 hours No space weather storms are expected for the next 24 hours.

The Penticton Observatory SFI value on 5-Dec-2005 at 2200Z was: 91 Solar activity is expected to be very low to low.

The NOAA Sunspot number for 5-Dec-2005 was: 85 Most recent five days (oldest first): 57 79 98 75 91