Dxers Unlimited
Dxers Unlimited's weekend edition for 26-27 March 2005
By Arnie Coro
radio amateur CO2KK

Hi amigos radioaficionados... from Havana, this is the weekend 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... 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 continue to forecast that   upcoming solar cycle 24 will be the worst in many , many years... as a matter of fact, the peak mean sunspot number expected is barely 75, something that will turn the frequency range above 20 megaHertz into the equivalent of a VHF band !!!... So, start to prepare for much lower solar activity to last for a loooong time amigos !!! Item two: DRM, digital radio mondiale broadcasts are definetely harming reception of regular , standard, AM double side band plus full carrier, A3 mode international shortwave broadcasts... Poorly adjusted transmitters used for the DRM transmissions are to be blamed according to experts, while other 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... This has led to several chief engineers at stations suffering from interference from DRM transmissions asking for those DRM broadcasts to be placed on a 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 non existent ..
Your comments about DRM broadcasts are invited amigos, just take a little time to send me your opinion about DRM to arnie@rhc.cu, 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 contest is in progress at the
moment you are listening to this show, and yes, you can pick up Tango forty
nine Charlie, the Cuban multi operator station now participating in the CQ
WorldWide WPX contest that every year sees stations from more than one
hundred and fifty countries active with the world's most rare callsigns...
In the case of this contest, what the winners will achieve is working the
greatest number of station's prefixes, as those are the multipliers of the
contest... Be on the lookout during your local evening hours on the 160, 80
and 40 meter bands, and possible on 20 meters too... Duringg daylight hours
the active bands for DX participants are going to be 20, 15 and 10 meters,
but with the present level of solar activity, 10 meters may be partially
open to some areas, or closed as if it were a VHF band !!! Operating during
amateur radio contests is always a challenge and is one of the more than 78
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@rhc.cu 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 weekend edition of Dxers Unlimited...it's the antenna
topics section, an answer to a problem that a Cuban radio amateur CM2TN is
facing with his G5RV antenna for the 80 to 10 meter bands... Rodolfo, CM2TN
called me on the phone as 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 for the
short version designed to work between 7 and 29.7 megaHertz and 13.4 meters
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... but
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, now in full swing here in the
Northern Hemisphere... At CO2KK my ham radio station I am picking up
amateurs from South America on the 6 meters band practically every day, with
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 50 megahertz band, 6 meters, with stations in Argentina,
Uruguay, Brazil, Paraguay and Chile during the equinoctial DX seasons.
...
You have QUESTIONS, and Arnie tries to answer them as soon as they arrive
here to my e-mail box arnie@rhc.cu, or at the postal address Arnie Coro,
Radio Havana Cuba, Havana, Cuba... Today's question came from Germany ,
where many listeners pick up our English language webcast that goes on the
air from 05 to 07 hours UTC... Amigo Dieter from Cologne asks if it is
possible to use a retired C band satellite dish antenna for amateur radio
work... Answer, sure amigo, you can turn that parabolic reflector into a
useful antenna for both terrestrial and space Dxing depending on the type of
mount that you decide to use. For terrestrial applications the typical 3
meters diameter C band retired satellite antenna will make an excellent
reflector for amateur radio bands in the range between 70 centimeters and 5
centimeters... but as I just said, it will require a rather expensive
mounting system so that the dish can be installed at enough height above
ground and also rotated in azimuth... Some amateurs that live at hilltop or
mountaintop locations have used the C band antennas at ground level, and
aiming them by hand with excellent results, but not everyone has the
priviledge of enjoying such excellent " made for VHF, UHF and Microwaves "
locations...
And now as always at the end of the program here is our exclusive and not copyrighted HF plus low band VHF propagation update and forecast... sunspot count around 65 , and there are possibilities of high latitude aurora borealis Saturday evening local time in North America, the effective sunspot number was very low Saturday morning my local time in Havana, with an estimated ESN, or effective sunspot number just around 25.. while the solar flux was near 80 .... and the A index at 18 units was showing the effects of a geomagnetic disturbance that will probably be ending by Sunday , certainly not very nice propagation conditions for those participating in the CQ World Wide WPX contests, but as I like to explain to contest operators, abnormal propagation gives them a challenge and the opportunity to work many rare DX ... See you all at the mid week 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@rhc.cu !!!