Re: [HCDX] Dxers Unlimited's mid week edition script for 12 -13 June 2007

["Prof. Arnaldo Coro Antich" <inforhc@xxxxxxx>]

Radio Habana Cuba
Dxers Unlimited
Dxers Unlimited's midweek edition for  June 12-13 2007
By Arnie Coro
radio amateur CO2KK

Hi amigos radioaficionados... from Havana, this is the midweek edition 
of your favorite radio hobby program the one and only featuring the most 
up to date HF plus low band VHF propagation updates and forecasts,always 
at the end of the show.
I am Arnie Coro, radio amateur CO2KK, your host here at Dxers Unlimited, 
a show devoted to the promotion and development of our wonderful hobby, 
yours and mine ... RADIO.

Item one: Scientists now have split opinions about the forecasts that 
upcoming solar cycle 24 will be the worst in many , many years, as a 
matter of fact, the peak mean sunspot number expected, according to one 
school of thought, is said to be barely 75, something that will turn the 
frequency range above 20 megaHertz into the equivalent of a VHF band for 
years to come !!!...

So, if we believe this forecast its about time to prepare for much lower 
solar activity to last for a loooong time amigos !!!

Item two: DRM, digital radio mondiale broadcasts are continuing to  harm 
reception of regular , standard, AM double side band plus full carrier, 
A3 mode international shortwave broadcasts...The reason has nothing to 
do with DRM broadcast technology at all, the main cause of this problem 
can be traced to poorly adjusted transmitters used for the DRM 
broadcasts that are to be blamed according to experts, while other 
highly qualified radio broadcasting engineers think that there is no 
room for DRM on the present high frequency international broadcast bands 
due to what they describe as an unforesought incompatibility between AM 
and DRM, in other words, they are appealing to special frequency 
spectrum allocations for DRM transmissions.
This started when  several chief engineers at stations suffering from 
interference from DRM transmissions asked for those DRM broadcasts to be 
placed on a separate  segment of the assigned bands , effectively giving 
them a sub-band,something that in my opinion may prove to be a very wise 
move. In the meantime DRM, digital radio mondiale continues to be heard 
by only a very small number of listeners , as low cost , practical 
receivers for DRM are still practically non existent for the public to 
buy...

Your comments about DRM broadcasts are invited amigos, just take a 
little time to send me your opinion about DRM to arnie@xxxxxx, or via 
air mail, send a postcard to Arnie Coro, Radio Havana Cuba, Havana, Cuba...

Now stay tuned, for more radio hobby related information coming to you 
from Havana... I'll be back in a moment , after a short break...
......

Si amigos, a nice worldwide radio amateur took place during the weekend 
but our main Cuban entry , special callsign station Tango forty nine 
Charlie, the Cuban multi operator ROVER station that participated in the 
ARRL June VHF QSO Party that every year sees VHF, UHF and Microwave 
enthusiasts from North America , Central America and the Caribbean 
taking part had to deal with extremely poor VHF 6 and 2 meters band 
propagation conditions...

In the case of this contest, what the winners will achieve is working 
the greatest number of grid squares, as those are the multipliers of the 
contest... !!!

Operating during amateur radio contests is always a challenge and is one 
of the more than 80 ways that you and I may enjoy this wonderful hobby...

Item four: More ham radio software available free of charge... at 
absolutely no cost, thanks to ham operators that make their programs 
freely available for the benefit of radio amateurs worldwide... among 
them the excellent propagation forecasting and nowcasting program by 
W6EL, by Sheldon C. Shallon, who wrote it in 2001 and then very kindly 
made it freeware....

I have used the W6EL propagation forecasting program for the last four 
years with excellent results, and it compares extremely well with 
professional, and I must add pretty expensive, software used for precise 
calculations of short wave radio communications. W6EL's program is very 
easy to use, and works on many operating systems, but so far I have not 
seen a LINUX version for it... In case you don't find W6EL's propagation 
software on the INTERNET's world wide web for downloading, just send me 
an e-mail and I will be very happy to send the dot zip file to you, as 
it is , believe it or not less than half a megabyte in size...

Send your request to arnie@xxxxxx amigos, and sorry, there is no 
practical way for me at this moment to send this software by other means 
than as an e-mail attachment amigos...

Item five at this midweek edition of Dxers Unlimited...it's the antenna 
topics section, an answer to a problem that a Cuban radio amateur was 
having  with his G5RV antenna for the 80 to 10 meter bands... He called 
  me on one of our local 2  meters band FM repeaters to say that he was 
having problems with this G5RV antenna... and we soon found out that his 
antenna tuner's capacitors were arcing between the rotor and stator 
plates. The problem only happened on 40 meters, and the automatic power 
shutdown of his recycled Yaesu FT80 will trip very often in the middle 
of a QSO.

After reviewing the setup at his station, I recomended that he changed 
the length of the open wire line feeding the G5RV antenna, and also that 
on 40 meters he used a one to one balanced to unbalanced antenna 
transformer instead of the four to one ratio he was using.

It seems like the impedance transformation done by the open wire line 
was making the antenna tuner's job a very difficult one.



Once he changed the balun, the problem just vannished. The interesting 
thing about this problem is that he could work on 80, 20, 15 and 10 
meters without any problem, and it was only when he attempted to operate 
on the 40 meter band that the problem knocked his station off the air.

I thought it would be a good idea to pass this along to Dxers 
Unlimited's listeners that are also amateur radio operators, because the 
G5RV compromise wire multiband antenna is very popular , despite the 
fact that it may act up on some bands as you have just heard. By the 
way, I have never installed a G5RV, as a fan dipole, fed with 400 ohms 
open wire length and with its legs between 11 and 25 meters long is a 
much better antenna by all standards.

Just remember to use three wires for each leg of the antenna and 
separate them at the end by about thirty percent of their length.

For example, one of my favorite compact fan dipoles uses 7 meters long 
legs, separated by about 2.3 meters, providing the user with an antenna 
that works very nicely from 40 to 10 meters .

A longer version about twice that size provides not only coverage of 80 
meters, but also some gain on the higher bands.

The separation between the upper and lower wires of the 14 meters long 
fan dipole is 4.6 meters, but let me add that this is not so critical, 
as I have used this fan dipoles with less separation between the wires 
with very nice results.

If you want to go by the book, the ideal length for these two antennas 
are 6.7 meters on each side of the dipole for the short version designed 
to work between 7 and 29.7 megaHertz and 13.4 meters on each side of the 
dipole for the version designed to work between 3.5 and 29.7 megaHertz..

The use 400 ohm impedance open wire line is essential to obtain the 
benefits of these antenna designs, and the actual length of the open 
wire line should be a bit more of a quarter wavelength at the lowest 
operating frequency , taking into consideration the velocity factor of 
the line, in this case about 0.92.

By the way, as an additional bonus, the fan dipoles are really broadband 
antennas, so they are excellent for monitoring purposes and listening to 
international short wave broadcasts from 6 all the way up to 26 
megaHertz, that is from the 49 to the 11 meters bands..
.....


This is Radio Havana Cuba, the name of the show is Dxers Unlimited, I am 
Arnie Coro, your host here at this twice weekly program devoted to all 
the different aspects of the radio hobby, from home radioastronomy to 
Dxing on the AM broadcast band with a crystal set... from working an 
amateur radio contest to wiring up your own low power QRP transmitter 
and using it on the air , accepting the challenge of operating with 
powers less than 5 Watts into the antenna.

Yes my friends, radio is never boring, because you can always learn 
about a new and fascinating way of enjoying it.

For example, communicating with ultra low power transmitters on the HF 
bands as done recently by radio amateurs has challenged some of the most 
advanced theories regarding communications using the ionosphere .

Theoretical analysis done in the past prescribed a certain minimum 
effective radiated power at the transmitting site in order to achieve 
contacts via the ionosphere, using powers in the range from 10 
milliwatts down into the microwatt region, has shown the amazing fact 
that signals do get back to Earth under some very special propagation 
conditions.

Another area of great interest explored by radio amateurs is 
transequatorial propagation.

At CO2KK my ham radio station I am picking up amateurs from South 
America on the 10 meters band practically every day, despite the 
extremely low solar activity and those are amazing signals considering 
the low powers used.

Even with a simple half wave wire dipole just 3 meters above my rooftop, 
I have made excellent two way contacts on the 28 to 29.7 megahertz 
band,10 meters, with stations in Argentina, Uruguay, Brazil, Paraguay 
and Chile during the equinoctial DX seasons, and now well into the summer .
...

And now our exclusive and not copyrighted HF plus low band VHF 
propagation forecast... Solar activity has again gone down to extremely 
low levels, as all the effects of the only big sunspot have totally 
faded away. So expect several days of very low solar activity with the 
daily solar flux barely reachin 70 units.
AND, let's wait and see if regular sporadic E openings begin to happen 
AFTER the contest, instead as when we needed them badly during the past 
weekend when the June VHF contest was taking place...
See you all at the next edition of the program amigos, and don't forget 
to take a little time now to drop me an e-mail with a signal report and 
your comments about today's Dxers Unlimited, send mail to arnie@xxxxxx 
!!! Or Send an AIR MAIL
Postcard to Arnie Coro, Radio Havana Cuba, Havana Cuba

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