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Re: [HCDX] Dxers Unlimited's mid week edition for 2-3 January 2007



Radio Havana Cuba

Dxers Unlimited

Dxers Unlimited's mid week edition

for January 2-3 2007

By Arnie Coro

radio amateur CO2KK


Hi amigos radioaficionados !!! Happy New Year 2007 !!! Welcome to the 
Year of the Quiet Sun, when solar cycle number 23 is expected to come to 
an end, although some scientists believe that it may last even until the 
middle of next year 2008...

I am Arnaldo, Arnie, Coro, radio amateur CO2KK, your host here at this 
twice weekly radio hobby program that started some twenty years ago as a 
once a week ten minute show, that was only devoted to short wave 
listening, and has evolved into the most comprehensive radio hobby 
program now in existence, according to feedback from listeners like you 
, who keep Dxers Unlimited as your favourite show... ASK ARNIE, 
continues to be LA NUMERO UNO, the most popular section of the program , 
but closely followed by the HF plus low band VHF propagation forecast 
that goes at the end of the show,and if you thought that the number 
three most popular section of the program was the one devoted to 
technical topics , you were right, and this one came tied with the 
antennas topics section... Now some of your New Year's wishes that I 
have received with the many e-mail messages wishing us here at Radio 
Havana Cuba a happy 2007... Among the requests were

to include more amateur radio hobby topics for beginners , now that in 
many countries, passing the amateur radio license test has been made 
easier by the removal of the CW Morse Code requirement. Another 
frequently mentioned request asks for more operating tips, including 
special propagation reports when amateur radio contests are approaching. 
Amigos, I want to thank you all very much for sending those valuable 
opinions, and be assured that Dxers Unlimited will continue to be your 
favourite radio hobby program , dealing with my now revised list of 80 
different ways you and I enjoy this wonderful way of spending our spare 
time in a most fascinating and relaxing way...

Stay tuned as the first Dxers Unlimited program of 2007 continues after 
a short break, I am Arnie Coro in Havana, back with you in a few seconds.

.....

You are listening to Radio Havana Cuba, the name of this show is Dxers 
Unlimited, and when it started some twenty years ago , it was supposed 
to be devoted only to short wave listening, but now, you can learn here 
about such interesting aspects of the radio hobby as home brewing ultra 
simple radios and accepting the challenge of picking up long distance 
stations with them, or installing a magnetic loop antenna to make 
possible operating your amateur station from a high rise apartment 
building where no external antennas are allowed, you can also enjoy 
listening to the technical topics section contents, guiding you trough 
sometimes controversial technical stuff, like the so called Crossed 
Field Antenna , or CFA, one of the greatest scams ever in antenna 
technology... No amigo the CFA antenna doesn't work at all, and as a 
matter of fact, at least two of those antennas sold to broadcast 
stations have been the subject of great controversy that ended up in 
court. The most recent one is a lawsuit by a station located in the Isle 
of Man, that was erroneously led to believe that a CFA antenna would be 
better than any other “classic” design ...

Si amigos, yes my friends, here at Dxers Unlimited, you can learn how to 
talk to ham radio operators via satellite using a hand-held dual band

FM transceiver, or show your children how radio and computers working 
together can make possible extremely low power two way contacts around 
the world...

Now, let's try to update the backlog of questions sent to ASK ARNIE 
during the past two weeks, when obviously many of you had a little more 
time to relax and listen to the radio, or surf the web and read the 
scripts of the program that are now available at several websites and 
mailing lists... Today's question, sent by three listeners, one in 
Canada, the other in Trinidad and Tobago and the third in Germany, they 
all three say in their e-mail messages sent to arnie@xxxxxx 
<mailto:arnie@xxxxxx> , that they want to know more about digital radio 
broadcasting and how I see its future... So , here we go... First of all 
digital radio broadcasting as we know it today provides listening to a 
very small number of radio's worldwide audience... That's a fact that no 
one can deny... Second: The existence of several different digital 
broadcast technical standards is making a very negative impact in the 
expansion of this new technology, and in the third place is the fact 
that radio receivers for picking up digital broadcasts are still rather 
expensive, and in many instances hard to find.

Digital broadcast technologies for local ground wave transmissions on 
both the AM long wave and medium wave bands, and also on the VHF FM 
bands, when received at a fixed site seem to work quite well now, and 
the audio quality that can be implemented is as good as one may want. 
But there are quite a few problems still to be solved when , for 
example, digital radio signals are received in areas where , in the case 
of AM medium wave broadcast band stations, the ground wave and the sky 
wave combine with each other randomly to produce a very annoying signal 
fading. Digital radio technology so far hasn't solved this problem, so 
when you are located inside that critical reception area, your radio's 
suddenly goes silent for certain short periods, a very annoying problem 
to say the least.

Digital radio broadcasts on the FM band suffer from a similar problem 
due to the so called multipath propagation , so when you are travelling 
on a vehicle and listening to a digital station, you are likely to 
experience the same annoying total drop outs in service.

Yes, of course, there are ways to go around this problem, but they will 
require a totally different technology that will include a high degree 
of redundancy into the digital streams, and a sophisticated receiver 
that will actually do a lot o signal processing before sending the audio 
to the loudspeakers or headphones !!!

Later in today's program, I'll tell you more about DRM, Digital Radio 
Mondiale's efforts to broadcast using short waves, that so far have 
proven to be a total failure.....

.....

Si amigos, 2007 is here now, and during the next 363 days we are going 
to watch how solar activity continues to go down, taking us into solar 
minimum... So be prepared for very poor HF propagation conditions that 
will keep the bands above fifteen megahertz totally dead ...

Now here is , as requested by many listeners, more information about a 
radio noise related topic... Those sending the request wanted to know if 
it is true that the new high intensity light emitting diodes lamps are a 
good replacement for the energy saving fluorescent electronic lamps that 
generate so much radio frequency noise.

Well amigos, so far the high intensity light emitting diode lamps that I 
have learned about seem to require the use of a certain number of those 
devices in order to achieve enough light output, as technology has not 
yet provided a large size light emitting diode , large enough to produce 
a light output similar to even a small 5 Watt incandescent bulb... But, 
let me say that I am still in doubt with the new high intensity light 
emitting diode replacement lamps, because I haven't had the opportunity 
of seeing how do they provide the low voltage required to operate the 
LEDs... If the low voltage is obtained by means of a simple dropping 
resistor and rectifier diodes combination, then the lamps will not 
generate radio frequency noise, but if some type of radio frequency 
oscillator is used, then they will cause interference to radio 
reception, as is the case with the present day energy savers fluorescent 
lamps that make radio reception so difficult wherever they are in use.

Been an experimentally minded person, as I am, during the long new 
year's eve weekend I decided to do some experiments with light emitting 
diodes that I were at hand. These are not the high intensity white light 
diodes, but served well for my purpose of testing the way that they can 
be supplied with the low direct current voltage required for their 
operation. I ended up with two really nice cluster lamps, one made with 
five red el e dees, and the other one made with five green ones...First 
thing I learned during the experiment was that the green diodes require 
a higher voltage to operate, and in second place was the fact that for 
some reason it was better to feed the diodes with individual voltage 
dropping resistors than placing them in series connection to use a 
single voltage dropping resistor... Anyway, the experiments were a 
success, but both lamps, the red and the green , had to be powered from 
a four and a half to six volts direct current source, that could be 
either three or four series connected batteries, or an AC power supply...

Now, I must wait for feedback from Dxers Unlimited listeners around the 
world, to provide your own personal experiences with the high intensity 
light emitting diodes lamps, in order to see if your results match with 
my experiments here, and the reason for having to ask you for this 
practical results is that so far I haven't been able to obtain some high 
intensity white light emitting diodes ...

So , if you have already tested the new white light high intensity LED 
lamps, please send the results of your noise tests to arnie@xxxxxx 
<mailto:arnie@xxxxxx>, again its arnie@xxxxxx <mailto:arnie@xxxxxx> , so 
that they can be shared with Dxers Unlimited's worldwide audience 
amigos... And don't forget that if you can obtain enough of those 
diodes, assembling your own lamp to replace the energy saving 
fluorescent noise maker nearest to your radio is certainly going to be a 
nice weekend project too...

.....

As promised, here are some comments about DRM , Digital Radio Mondiale 
broadcasts of short wave and the problems they are causing to other 
stations using the classic AM technology... According to the opinion of 
a senior Cuban broadcast engineer that has observed several DRM 
transmissions using sophisticated spectrum analysis hardware and 
software,he is of the opinion that most of the time the excessive 
bandwidth used by the DRM signals has to do with poorly adjusted 
transmitters, mentioning that DRM's is a very demanding transmission 
mode that requires an extremely linear transmitter, something that in 
his opinion is not possible from older equipment forced to broadcasting 
DRM signals....

And now amigos as always at the end of the program... here is Arnie 
Coro's Dxers Unlimited's HF , plus low band VHF propagation update and 
forecast...

Solar activity is now oscillating from very low to low,solar flux around 
90 units, and a high speed six hundred kilometres per second solar wind 
is causing some geomagnetic disturbances. The solar active sunspot 
region that produced the big X flares during the previous rotation is 
back now, but it has decayed, so only class C or an occasional class M 
flares are expected. The winter sporadic E season is about to come to an 
end now, as we move away from the winter solstice... Enjoy the radio 
hobby amigo,and share

your experience with others by sending me your comments and questions to 
arnie@xxxxxx <mailto:arnie@xxxxxx> or VIA AIR MAIL to Arnie Coro, Radio 
Havana Cuba, Havana, Cub


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