Re: [HCDX] Dxers Unlimited's mid week edition for 7 -8 August 2007

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

Radio Habana Cuba

Dxers Unlimited

Dxers Unlimited's mid week edition 7-8 August 2007

By Arnie Coro

radio amateur CO2KK

 

Hi mis amigos radioaficionados around the world and in space.. 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: One single solar active 
region on sight...... it has already produced class B and C flares and 
scientists predict that more are possible.

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 ... Item two: The electromagnetic ground plane single 
band antenna for amateur radio stations reviewed during a recent edition 
of Dxers Unlimited brought a lot of feedback from ham operators around 
the world... I have already sent out more than twenty 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 I warn you...it does has two drawbacks... 
you have to adjust the antenna system 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, and 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...

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, cellphones are practical, 
cellphones are convenient... but each cellphone system has a preset 
capacity to create links, and what 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 any communications emergencies. 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 at very low levels, with solar flux barely 
moving above 70 units... The effects of a high speed solar wind are now 
subsiding, and the geomagnetic field is expected to be back to normal 
when you are hearing this program. The all over darkness path from the 
Caribbean to Australia is providing excellent reception of short wave 
stations during the local time period here extending from about one o 
clock in the morning, that is zero five hours UTC until a few minutes 
after local sunrise... It is certainly a very interesting propagation 
path that radio amateur have enjoyed for 40 meters band contacts at this 
time of solar minimum  activity, I hope to have  you listening to our 
weekend edition next Saturday and Sunday UTC days , and also don't 
forget to send me your signal reports and comments about the program as 
well as any radio hobby related questions to arnie@xxxxxx 
<mailto:arnie@xxxxxx>, again arnie@xxxxxx <mailto:arnie@xxxxxx> or VIA 
AIR MAIL to Arnie Coro, Radio Havana Cuba, Havana, Cuba

 

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