[BARC-List] Dxers Unlimited's mid week edition for 14-15 March 2006

[Dan Malloy]

Radio Havana Cuba 
Dxers Unlimited 
Dxers Unlimited's mid week edition for 14-15 March 2006 
By Arnie Coro 
Radio amateur CO2KK 

HI amigos radioaficionados worldwide ! This is the mid week edition of Dxers
Unlimited coming to you from Havana, when solar activity continues to be at
very low levels , as we are seeing solar flux figures at very near the
minimum ever registered since that solar parameter started to be monitored. 
The very low solar activity brings also very low ionospheric absorption,
something that provides a very interesting scenario for the next three weeks
when we will go trough the Northern Hemisphere spring equinox and the
Southern Hemisphere autumn equinox, and that means that solar radiation is
equally spread all over Planet Earth for a short but very rewarding period
of time.Long distance HF propagation conditions are going to be very good
amigos ! Especially along the frequency range from 3 to 18 megaHertz. 
Item two: Testing 2 meter band handheld transceivers donated to our Radio
Club by a local company that replaced all of its communications equipment,
we found out that the handie-talkies could be reprogrammed to operate on the
2 megaHertz wide 2 meter amateur band here in Cuba. But that required us to
find both the soft and the hardware to enable our club's technical guru to
program the ninety nine available channels. At short notice, the guru
produced an optimized table of frequencies that included all the repeater
input and output frequencies , as well as our national priority channel 145
500, that has proven so useful during emergencies, as every Cuban radio
amateur knows that if no repeaters are within reach, monitoring 145.500
provides the best chances of establishing a communications link. 
A few days after receiving the donated FM transceivers, we were able to have
a lot of them in full operational condition, ready to go for the upcoming
Atlantic Hurricane Season, due to start next June first. Last year more than
one thousand Cuban radio amateurs took part in hurricanes related emergency
communications nets, and most of the traffic was done on precisely the two
meters band, thanks to the efficient network of repeaters that the Cuban
Federation of Radio Amateurs has helped to install and maintain. Long range
traffic goes on 40 and 20 meters, providing effective coordination with
other Caribbean nations located in the path of a storm. The excellent Cuban
Weather Service forecasts are also made available a few minutes after they
are written, because there is an amateur radio station located at the
headquarters of the Instituto de Meteorologia, the meteorology institute's
main venue in Casablanca, a small town across the Havana harbor. 
Among the things we have learned since the year 2000 , when stronger and
stronger tropical hurricanes have struck Cuba, is that emergency stations
need to have a good and reliable energy supply, and that standby antennas
should be ready to go up in case one looses the station's antenna during the
storm. 
As many of you already know, scientists are forecasting a very active 2006
Atlantic Hurricane Season, and that's why we are getting ready for it. 
Standby for more radio hobby related information coming to from Havana after
a short break 
.. 

Si amigos, yes my friends, this is Dxers Unlimited's mid week edition, and
here is our most popular section of the show, the one we devote to answering
your radio hobby related questions. Now listen to this one, as it is unusual
to say the least. It comes from listener Alex in North Carolina, and he
wanted to know why his neighbor's dog that has a special collar to keep him
within the front garden, starts to bark desperately whenever Alex started
using his 2 meters band FM transceiver. Well amigo, the secret of what's
happening was inside the neighbor's  dog special collar. I was  practically
sure that your two meter signal is somehow getting into the collar's
electronic circuit, and giving the dog a jolt every time you punch the push
to talk button of your 2meter rig. 
The area restraining collars work by picking up a signal from a buried
underground loop that when detected by the collar, gives the dog a small but
certainly unpleasant electrical shock. The dog then learns that it is very
convenient to stay away from the perimeter set by the buried wire.. But
apparently the dog collar's circuit was not fully protected against local
radio amateur's 2 meter band signals, that also trigger the electric shock
delivery , even when the dog is well away from the buried cable that makes
the system work. 
Now, as always, with any type of radio frequency interference you have to
handle it with great care and diplomacy. For example, you may ask your
neighbor to loan you the collar for a few hours, and even invite her or him
to be present when you open up the collar in search of the part of the
electronic circuit that may be receiving your 2 meters band signal and
activating the electric shock to the dog. Fortunately, amigo Alex has a good
background in practical electronics, and following my advice, he installed a
pair of radio frequency chokes of 2.3 micro henries inductance, and two
small disk ceramic bypass capacitors at the input of the dog's collar sense
coil. Now, not even running 500 Watts of CW on 144.200 will activate the
dog's collar.. 
So, the DOG COLLAR INTERFERENCE mystery was solved and now amigo Alex can
talk to all of his friends on 2 meters without hearing his neighbor's dog
barking at full power !!! 
... 
You are listening to the mid week edition of Dxers Unlimited, my direct
e-mail address is arnie at rhc.cu, again arnie at rhc.cu, and VIA AIR MAIL you can
send your postcards of letters to Arnie Coro , Radio Havana Cuba, Havana
Cuba.Here is now our next radio hobby related item. the antenna topics
section, one of your favorites is now on the air. Today, also answering a
question, I will tell you about coaxial cable losses, and why it so
important especially for long runs of cable when you are attempting to pick
up VHF and UHF frequencies. A few days ago a regular Dxers Unlimited's
listener sent an e-mail and asked me about why he was picking so few
stations with his new scanner , despite what he thought was a very nice
antenna installation. Amigo Arthur had installed a homebrew diskcone antenna
that he built using information I sent to him last year. He found out that
the diskcone worked very well when placed at his balcony rail, but contrary
to what he thought would happen, the antenna's performance actually went
down when he installed the diskcone six stories above his four stories high
apartment. In other words, he had to run a rather long length of coaxial
cable to connect the antenna that was now installed on a four meters high
mast on the building's rooftop . Arthur asked me via e-mail what I thought
was happening, and my reply had just one line: 
It read: Art, please tell me the type of coaxial cable you used to feed the
rooftop antenna. 
The answer came back that same evening: 
It read: Arnie, its RG58U coaxial cable, and the full length is 
220 feet, that I immediately converted to metric with my solar powered
calculator; almost exactly 67 meters. 
Then I went to a wonderful little book written by my very good friend NA5N,
Paul Harden, the name of the book is 
Data Book for Home brewers and QRPers, and sure enough 50 ohms coaxial cable
losses are listed there. As amigo Art wanted to use his diskcone for the
frequency range from 50 megaHertz all the way up to one GIGAHERTZ. that his
nice scanner covers. I could answer him back in just a few seconds with the
following one line e-mail 
Text: Art, need to change your RG58A cable, because attenuation at 50
megaHertz is at the very high figure of 3.3 decibels for each 100 feet or
roughly 30 meters. In a follow up e-mail I told art that if he really wanted
to use this diskcone antenna at the rooftop location, he would have to spend
a lot of money to buy very special low loss coaxial cable, because the
losses at the higher than 50 megaHertz frequencies are much more higher. 
The e-mail dialog continued, and Art ended up by following my advice,
installing his diskcone antenna using the balcony rail as the support and
connecting it to the radio using a short length of a low loss coaxial cable.
After finishing the installation , Art e mailed back to me, saying that he
was picking up air traffic a couple of hundred miles away on the VHF AM
aviation band that starts at 118 dot zero megahertz, and that he could also
pick up several amateur band repeaters on the 440 megaHertz band. The story
of what amigo Art did with the long run of RG58-U cable has a happy ending,
as he kept split the cable into four equal lengths of about 55 feet  or 17
meters each, kept two of them for his portable monitoring station, and gave
the other two rolls away at a radio club meeting, not before telling
everyone present to be extremely careful when using coaxial cables that are
to be used at frequencies above 50 megaHertz ! 
... 
Absolutely fascinating, that's the way to describe the unique thrill
experienced when picking up the long wave AM broadcast stations from Europe,
Africa and the Middle East here in the Americas. The extremely low
ionospheric absorption associated with periods of very low solar activity
that last for several days, provide almost ideal conditions for those long
wave stations to cross the Atlantic. Here in Havana, using a Russian built
consumer receiver that goes by the name of SELENA 205, I have recently heard
several long wave stations with very nice signals, and they provided me with
a nice tip to go up higher in frequency to search for the standard AM
broadcast band European stations that use 9 kiloHertz channel spacing
instead of the 10 kiloHertz spacing used in the Americas. 
And now amigos, as always at the end of Dxers Unlimited, here is our
exclusive and not copyrighted HF plus low band VHF propagation update and
forecast. Solar flux is very low, and will stay below 80 units for the next
several days if no new sunspot regions show up. The heliosysmic solar
analysis show that there are no big sunspots on the side of the Sun that we
can't see from Earth. Equinoctial propagation conditions are now in full
swing, as the spring equinox is just a few days away.Expect also possible
VHF tropo ducting in the Gulf of Mexico and northern Caribbean if an
upcoming cold front becomes stationary.No sporadic E events are expected
until a few weeks from now, when the summer E skip season is due to start.
Hope to have you listening to the weekend edition of Dxers Unlimited this
coming Saturday and Sunday UTC days amigos. And don't forget to take a
little time to send me your comments about the program and radio hobby
related questions. mail to arnie at rhc.cu or VIA AIR MAIL to Arnie Coro, Radio
Havana Cuba, Havana, Cuba