Re: [HCDX] Dxers Unlimited's mid week edition for 10 -11 July 2007

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

Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited's mid week edition for July 10 -11 2007
By Arnie Coro
radio amateur CO2KK


Hi amigos radioaficionados around the world and orbiting planet Earth 
aboard the International Space Station... you are certainly most welcome 
to the mid week edition of Dxers Unlimited, coming to you from sunny 
Havana, where practically every afternoon we are having to deal with 
powerful thunderstorms. Our weather experts say that they are the result 
of the daytime heating of the Earth , and in our particular location, an 
area of very shallow sea, the Gulf of Batabano, located some 40 miles 
south of the Cuban capital, seems to provide an enourmous amount of 
water that
is transformed by the Sun's infrared energy into water vapor that  feeds 
the powerful cumulus nimbus storm clouds that drift from South to North 
into our metropolitan area .
And talking about summer thunderstorms that every year destroy a large 
number of radios and other high tech solid state microprocessors 
controlled equipment ...
Several Dxers Unlimited's listeners, worried about the summer 
thunderstorms causing damage to a lot of sensitive solid state 
electronic equipment, have recently sent e-mails to the ASK ARNIE 
section of the program, with a very interesting question. They all want 
to know if the fact that in the placewhere they live the electrical 
distribution system is underground, that is, no overhead wiring is used, 
their radios , computers, stereos and other equipment are better protected.
Here is the answer: NO, don't think that because electricity reaches you 
from an underground distribution network you are better protected 
against lightning damages.
Whenever a close electrical strike hits your immediate vecinity, you 
know, the kind of lightning that shows very little time difference 
between the light flash and the thunder, a tremendous amount
of energy is unleashed, including radio frequency generated by the 
lightning discharge... yes you heard it right, radiofrequency energy, an 
enormous peak of radiofrequency energy that covers a very wide range of 
the radio spectrum... And , also, not to be forgotten, a huge high 
voltage , high current spike that either attempts to reach ground , or 
that goes from the ground up to the thunder cloud.

As a matter of fact, solid state electronics is extremely fragile , it 
is certainly much less rugged than the classic vacuum tubes electronics 
that preceded it.  I have heard recently from several experts , that at 
this moment  there is a great concern among aircraft pilots, aviation 
maintenance engineers and flight safety experts about the extreme 
vulnerability of the new generation of aircraft equipped with solid 
state electronics in general and computers in particular,  that may fail 
catastrophically  in case of a direct lightning strike to the plane, or 
even to an accumulation of static electricity when the plane is flying 
near highly charged cumulus nimbus clouds .
At least two aircraft accidents that I have heard about may have been 
originated by lightning hitting a brand new aircraft that shortly after 
take off entered a thunderstorm in one case, and static electricity 
accumulation in the other.
So amigos, play it safe, during the summer season be especially careful 
with all your radios, computers, stereos, and as a good friend likes to 
say, even the microwave oven, simply disconnect all equipment from the 
power lines, and don't forget to also disconnect the grounding system 
too. As Sherlock Holmes used to say to Doctor Watson, don't forget also 
to unplug and disconnect all of your antennas... elementary my dear 
Watson, elementary...

...........
Si amigos, yes my friends, oui mes amis, you are listening to the mid 
week edition of Dxers Unlimited, your favorite listener oriented radio 
hobby program, coming to you from Havana, and here is our next item 
...Closely related to the summer thunderstorm season... For those of you 
living in areas where thunderstorms are frequent, an excellent accesory 
to add to your shack is a lightning detector connected to an aural and 
visual alarm, or even interconnected so that your equipment is 
automatically shut down as soon as the detector picks up low frequency 
radio signals coming from the nearby approaching storm. Such an 
electronic device is not difficult to design, because Mother Nature 
helps us by providing high intensity radio signals every time that a 
lighting bolt strikes the Earth or jumps across to heavily charged 
clouds. The radio signal is picked up by the alarm system, rectified 
into a direct current that is then amplified and used to trigger the alarm.
The threshold level of the thunderstorm alarm system can be easily 
adjusted to generate a warning signal well ahead of the arrival of the 
core of the storm.
Again, the circuit of the thunderstorm warning alarm is rather 
straightforward , a ferrite rod or a loop antenna, a low frequency wide 
band radio receiver, plus the rectifier and control system that is then 
used to trigger the aural and visual alarms by means of a mechanical 
relay or a solid state switch.
If you live in an area frequently hit by thunderstorms, home brewing a 
storm warning device or buying a commercially built one will certainly 
increase the chances of your valuable electronic
equipment of surviving , because you will be able to disconnect it 
before the storm is overhead...
.......

Now here is our technical topics section, that today will be devoted to 
recent developments in battery charging technology, that promise to 
prolong the life of rechargeable batteries a lot. This
new generation of so called intelligent battery chargers make use of 
sophisticated electronics and also charge the batteries in a very 
different way than the traditional chargers. Be aware that some rather 
new types of rechargeable batteries do require special chargers , 
especially designed for them. The lithium-ion rechargeable batteries 
have to be dealt with very carefully , and they must only be charged 
with the especially designed charger for them... because they can catch 
fire and even explode if improperly charged. The use of the new 
generation of battery chargers with voltage and current , as well as 
temperature sensing can be extended to older , classic technologies with 
many benefits. Standard nickel cadmium batteries when charged using 
pulsed direct current of a certain specific pulse width, have stayed 
alive well after their expected lifetime. The same applies to the higher 
current density nickel metal hydride batteries .
Do remember to keep your battery chargers contacts very clean, closely 
monitor them when in use, and don't forget to replace the alkaline long 
or lithium long life batteries required by many devices to keep the 
internal clocks and settings at regular intervals. There are some 
instances of solid state radios that not only loose their settings when 
the memory back up batteries die, but that even require complete 
reprogramming if that happens...
Last but not least, if you happen to live in areas where tropical storms 
or hurricanes may strike , keep your emergency batteries in good shape, 
and whenever possible buy a small solar panel that can be used to 
recharge the batteries after the storm is over, because as many of us 
know very well, a huge tropical storm can leave a widespread area 
without electrical service for several days or even weeks !!!
.....
You are listening to Radio Havana Cuba, the name of the show is Dxers 
Unlimited, and yes we do QSL, we verify reception reports sent to us via 
e-mail to arnie@xxxxxx or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba, 
Havana, Cuba... Here is now our next item of this mid week edition of 
the program...A VHF- UHF and Microwave radio contest is to take place 
during this coming weekend... It is sponsored by CQ Radio Amateur 
Magazine, and it usually provides VHF operators with very good 
opportunities to add new countries and grid squares to their records. If 
good sporadic E layer openings happen during the weekend, the contest 
scores rise dramatically, but if the openings are few , then operators 
must rely in much more sophisticated communications modes like meteor 
scatter propagation or even Earth Moon Earth two way contacts, that with 
present day technologies are much easier than how they were five or six 
years ago. Using sophisticated computer programs and computer optimized 
antenna arrays, meteor scatter contacts are now much easier to complete, 
and single Yagi antenna stations, running output powers of less than 200 
Watts are able to complete two way earth moon earth contacts with some 
of the big stations that listen at the low end of the two meters amateur 
band. Si amigos, yes my friends, VHF contests are quite different from 
the ones that take place on the HF or short wave bands, they are 
certainly more challenging  and luck seems to play a much more relevant 
role, because if you are in an area where a nice sporadic E skip opening 
happens, then you can achieve extremely high contest scores, even while 
running a very modest station !
........

And talking about VHF and UHF propagation, let me add that TV and FM 
broadcast band DXers are now enjoying the peak of the summer sporadic E 
skip season, that already has produced some very nice double hop skip... 
I was recently able to pick up an FM station in Colorado, at the same 
time that another one from Texas was coming in, and that was a very 
positive indication of a double hop sporadic E skip event. The Texas 
station was very strong, while the one in Colorado was fading in and 
out, but luckily at the top of the hour the station ID came through very 
clearly... I was using my wide band 40 to 160 megaHertz broadband 
antenna, that is almost omnidirectional, so the sporadic E propagation 
was pretty strong . Normally TV DX and FM broadcast band Dxers use  two 
  different antennas, a broadband omni as mine, and a rotatable log 
periodic capable of picking up signals between 50 and 250 megaHertz. TV 
and FM broadcast band Dxing is a lot of fun, especially when you are 
able to record the signals on tape to show them to your visitors... 
adding that in most cases they won't believe what they are seeing, 
saying that those signals came to your set via satellite !!!

..







---[Start Commercial]---------------------

Preorder your WRTH 2007:
http://www.hard-core-dx.com/redirect2.php?id=wrth2007
---[End Commercial]-----------------------
________________________________________
Hard-Core-DX mailing list
Hard-Core-DX@xxxxxxxxxxxxxxxx
http://montreal.kotalampi.com/mailman/listinfo/hard-core-dx
http://www.hard-core-dx.com/
_______________________________________________

THE INFORMATION IN THIS ARTICLE IS FREE. It may be copied, distributed
and/or modified under the conditions set down in the Design Science License
published by Michael Stutz at 
http://www.gnu.org/licenses/dsl.html