Re: [HCDX] Dxers Unlimited's mid week edition for 27-28 February 2007

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

Radio Habana Cuba
Dxers Unlimited
Dxers Unlimited's mid week for 27-28 February 2007
By Arnie Coro
radio amateur CO2KK

Hi mis amigos radioaficionados... Hello short wave listeners, radio 
amateurs, TV Dxers, Low frequency LOWFERS, homebrewers of radios... 
hello to all of you my good friends and listeners of Dxers Unlimited. I 
am Arnie Coro, radio amateur CO2KK, and as always, its my pleasure to 
share with you about seventeen minutes of airtime... Here is now today's 
program menu: Item one: Very few sunspots, as expected during solar 
minimum, and that has sent the daily maximum useable frequency curve way 
down... as expected. More about sunspots and short wave propagation 
later , at the end of the show when I will be presenting Arnie Coro's 
Dxers Unlimited HF propagation update and for the next four days... Item 
two: The electromagnetic ground plane single band antenna for amateur 
radio stations is a very special type of antenna that I have already 
talked about here at Dxers Unlimited but it continuues to bring a lot of 
feedback from ham operators around the world... I have already sent many 
  e-mail messages with all the information, including graphics and a 
table of measurements to help build the EMGP antenna for different 
amateur bands... The EMGP is a very low height antenna system that 
although it requires very small masts, its radiation efficiency compares 
to a full size quarter wave vertical antenna system. BUT, as always you 
don't get something for nothing. and this antenna does has two 
drawbacks... you have to adjust it very carefully for a center frequency 
of operation and there is not a lot of bandwidth either side of the 
optimum frequency to which the antenna is tuned, also  matching the 
antenna to the typical 50 ohm coaxial cable downlead may be a time 
consuming job. But on the brighter side, once the antenna is adjusted it 
is a set and forget procedure.... I tested several EMGPs and although 
the tests were not over a long period of time, the EMGP compared to a 
standard reference half wave dipole at the typical height that we radio 
amateurs can install HF antennas, produced very nice results...That's 
because it is certainly a lot take off angle radiator... the low angles 
you want to work DX amigos !!!
If you want to know more about the EMGP low profile single band antenna 
, just send me an e-mail to arnie@xxxxxx, again, arnie@xxxxxx, or VIA 
AIR MAIL, send a postcard to Arnie Coro, Radio Havana Cuba, Havana, Cuba 
, more radio hobby related information coming up in a few seconds after 
a short break. This is Radio Havana Cuba, you are listening to Dxers 
Unlimited's mid week edition, stay tuned...
....

Si amigos, yes my friends, sure, there are many ways to enjoy our spare 
time by playing with our radios, antennas and all the associated 
equipment... Take for example the wonderful time spent assembling a new 
two meters or 70 centimeters band repeater that will be placed at a high 
rise building or maybe at a TV transmitter site way up atop a mountain, 
to provide coverage of an extensive area when using just small hand held 
FM transceivers or mobile radios installed on cars and trucks. Two 
meters and 70 centimeters band repeaters, when properly installed and 
mantained have proven, once and again, that they are able to provide 
excellent quality and very reliable communications links during 
emergencies, when many commercial systems just fail due to heave 
traffic... Yes cellphones are wonderful, but each cellphone system has a 
preset capacity to create links, and when that capacity is exceeded, the 
cellphone base stations simply fall into a lockout mode... something 
that simply can't happen with an amateur band FM repeater... Here in 
Cuba, we have assembled and installed many two meter band repeaters 
during the past 5 years, and they have proven to be really useful during 
the recent communications emergencies that happened when several 
hurricanes have struck our archipelago ... one of them was hurricane 
Dennis, the fourth tropical storm of a very active season, that reached 
up to Category 4 in the Saffir-Simpson scale that has a top limit of 5. 
More than eight hundred Cuban radio amateur operators volunteered their 
services during the hurricane Dennis emergency in 2005, providing vital 
links between weather stations, high power weather radar installations, 
the command posts of the National Civil Defense organization and many 
other sites, like the water reservoirs . If your local radio club has a 
two meters or a seventy centimeters band repeater, or for that matter an 
FM repeater operating on any of the amateur bands authorized for that 
type of automatic station, by all means help the persons running and 
mantaining the repeaters... One never knows when the next emergency will 
come out of nowhere and that nice repeater station that you normally use 
to chat while driving to work, may turn into the most useful 
communications tool to handle emergency traffic !!!
.......
This is Dxers Unlimited's mid week edition amigos, and here is item five 
: YOU HAVE QUESTIONS AND ARNIE TRIES TO ANSWER THEM, the most popular 
section of this program according to the statistics of our 
correspondence department ... Today's question, came from seven 
listeners located at such distant places as Alaska, Japan, New Zealand, 
Sweden , Ireland, India and Malaysia... They all want to learn more 
about the compact MOXON rectangle antenna system and why I have 
recommended it so much to Dxers Unlimited listeners... Well amigos, the 
MOXON rectangle antenna has a unique property as compared to a standard 
2 element YAGI antenna... and it is the fact that one can build a MOXON 
RECTANGLE antenna so as to make it a very rugged system, that can stand 
extremely high wind gusts without been damaged.
Some 2 meters band repeater operators are now using the MOXON rectangle 
antennas at sites where wind gusts may peak regularly above the 80 to 
100 miles per hour mark... While classical arrays of half wave dipoles 
may fail under such harsh weather conditions, the Moxon rectangle arrays 
stay up, increasing the all important reliability of the repeater even 
under stormy weather conditions.
Now, I am sure you all will want to know why the MOXON RECTANGLE antenna 
offers that high reliability,and the reason is no other than its 
mechanical design.
Contrary to the very exposed to wind gusts induced vibration typical of 
dipole elements, the MOXON's closed rectangle construction makes this 
antenna a very rugged radiating system. If built using large diameter 
copper pipe, a MOXON antenna for the 2 meters or 70 centimeters bands, 
will provide very good operating bandwidth and high reliability even 
under the most extreme weather conditions.
One further advantage of the MOXON antenna , is that it is very easy to 
build using common tools and readily available materials. The ones I 
have built here for the 6 meters band work very well and can be easily 
rotated by hand, because by building them using lightweight materials , 
this antenna is easily transportable and makes an ideal one for contest 
operation from a remote site.
So far I have seen MOXON RECTANGLE antennas made by using copper wire 
and fiberglass spreaders for the 20, 17, 15, 12 and 10 meter bands...
The MOXONS are single band antennas, that provide an apparent gain 
similar to a well designed 2 element Yagi , but that are more rugged and 
easier to build than the YAGIS, especially for the HF bands...
I hope that this answers your questions about the MOXON Rectangle 
antenna, and for all of you highly motivated with antenna design, a 
visit to www.cebik.com, will allow you to learn a lot more about this 
compact and efficient antenna, that also has an additional advantage, 
because it matches to 50 ohms coaxial line really well...
....
You can send your radio hobby related questions directly to my e-mail 
address... its's very easy to remember... arnie@xxxxxx, again, 
arnie@xxxxxx, and VIA AIR MAIL, send a postcard to Arnie Coro , Radio 
Havana Cuba, Havana , Cuba, and now here is another very popular section 
of Dxers Unlimited, our technical topics section ... Today 's tip is 
related to the revival of gell cell sealed accumulators... the ones used 
for computer UPS systems, home alarms and of course portable low power 
amateur radio stations... The typical gell cell accumulator is capable 
of providing either 6 volts or 12 volts, at current ratings that go from 
about 4 to 10 ampere hours... Anything higher than 10 ampere hours will 
be rather large sized and bulky...
If you take a look at the typical gell cell accumulator, you will see 
that it is totally sealed, and there is no way to add electrolyte or 
deionized water to each of the
battery elements connected in series to provide 6 or 12 volts to our 
radios...
Here is what I do here to revive GELL CELL accumulators, although after 
using the process to be described, the GELL CELL battery can no longer 
be moved around as it will be loosing its "sealed" nature.
Well, what I do is simply to drill trough each of the battery cells so 
that deionized water or battery electrolyte can be added with the help 
of a plastic syringe.
Be extremely careful when handling the battery and the electrolyte, and 
after topping up each cell, then proceed to put back the plugs, recharge 
the battery at a rate of one tenth of its capacity , and then run a test 
with your radios... In most cases I have obtained very good results that 
have prolonged the useful life of the GELL CELL ACCUMULATOR , for up to 
one more year of continuos use.
.....
And now amigos , ready to copy, here is our exclusive and not 
copyrighted HF plus low and VHF propagation update and forecast... Solar 
activity has continued to be very low with the effective sunspot number 
at a rather low figure. The solar wind gust that was expected to impact 
the Earth's magnetosphere simply didn't happen, and that's good news for 
those of you living a latitudes above 40 degrees North, where the impact 
of those proton showers really make the ionosphere behave very poorly 
....now much higher than one week ago....Solar flux is running around 75 
units, with the A index at a nice and low 03 around 15 hours UTC 
Tuesday, the effective sunspot number was 15 at that same time, and the 
optical sunspot count went up to 22 on Monday… Hope to have you 
listening to the weekend edition of Dxers Unlimited next Saturday and 
Sunday UTC days, and don’t forget to send me your signal reports and 
comments about the program to arnie@xxxxxx, of VIA AIR MAIL to Arnie 
Coro, Radio Havana Cuba, Havana, Cuba
 
 
 
 
 
 



---[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