Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited's mid week edition Dec 12-13 , 2006
By Arnie Coro
radio amateur CO2KK
Hi amigos radioaficionados worldwide ! Your short wave receiver is now
tuned to Radio Havana Cuba's twice weekly radio hobby program, Dxers
Unlimited, with yours truly, Arnie Coro at the microphone. Here is item
one: Solar activity now moving down, as so far no more big sunspots
followed the active region that generated two X class solar flares....
Item two: DRM, Digital Radio Mondiale totally stalled according to the
opinion of mass media experts, that rightfully have voiced their
opinions that without low cost radios capable of picking up the DRM
short wave broadcasts , the digital transmission system is doomed to
failure. Besides the lack of receivers at a reasonable cost , those who
have already experienced DRM reception not at a one day demonstration,
but on a regular , daily basis, are telling engineers that the total
drop out of the audio output experienced by DRM broadcasts is very
annoying to say the least. For those of you not familiar with DRM,
Digital Radio Mondiale, it is a standard specifically created to
broadcast digitally instead of using the classic analog radio modulation
technologies, AM and FM that we listen to every day. Stations
broadcasting using DRM have not made public audience research statistics
or comments by potential listeners, something that in my humble opinion
really doesn't help DRM at all, because lack of such information is
something to worry about. According to several mass media researchers,
the pattern followed during the introduction of DRM technology for short
wave broadcasting is basically wrong, because low cost radios for DRM
reception have not become available yet, and besides that, the promotion
of the technology has also been mishandled by the DRM Consortium, who
seems to be much more concerned about the engineering problems regarding
the transmitters than with the actual reception of the broadcasts.
More about digital communications modes later , as Dxers Unlimited's mid
week edition continues.. I am Arnie Coro in Havana,
.......
Si amigos, yes my friends, I want to ask each and everyone of Dxers
Unlimited listeners around the world a single question today... Get
ready for writing it down, as I think this is going to be one of the
first ever open polls about DRM Digital Radio Mondiale.... In a couple
of minutes I will be formulating the question, to give you a chance to
find paper and a pen or pencil to write it down.. In the meantime let me
add that radio amateurs are using digital communications modes with a
high degree of reliability and energy efficiency... A keyboard to
keyboard narrowband mode, PSK31 is now , at the low ebb of the solar
cycle, becoming more and more popular among those amateur radio
operators around the world that have learned how to connect their
computers to their radios . PSK31 running between 10 and 25 Watts power
has proven to be extremely effective on the 20 meters ham band, and as
recycled computers become cheaper and their availability increases, more
and more radio amateurs around the world are learning how to communicate
using PSK31.... Now, ready for today's question... Here we go...
Ready to copy: Here we go:
Have you ever listened to Digital Radio Mondiale, DRM
broadcast transmissions on short wave ?
Again, here is the basic question
Have you ever listened to Digital Radio Mondiale , DRM broadcasts
transmission on short wave ?
And in case that your answer is yes:again, in case your answer is yes,
give your impressions about those DRM broadcasts regarding quality and
reliability of reception.
So, in case you have listened to DRM add your comments about quality and
reliability of reception to your YES answer to the question.
As soon as all the answers are received here, I will compile them and
analyze them using standard statistical methods, and of course, made the
results of this poll public, by reading them on the air, and publishing
them on our website.
Your answers about DRM will certainly help to have a much better picture
of what's happening with this technology amigos !
.......
Now, let's go to Arnie's workshop, where an antenna project is in the
works, to help several of the new local radio amateurs that have
recently obtained their ham radio license. This antenna is very easy to
homebrew and has a very low cost. Readily available materials are used
in the project and each antenna comes out of the workshop adjusted for
minimum standing wave ratio .
This is a variation of the so called SLIM JIM antenna, made using
standard 300 ohms Television twinlead and a length of PVC pipe. The
antennas here in Cuba are cut for 145.2 megaHertz , so that they will
provide the lowest possbile standing wave ratio between 144.5 and 145.5
megaHertz, the most used part of the two meters band all along the Cuban
archipelago. Cuban 2 meter band repeaters operate between 145.110 and
145.490
with one odd frequency repeater in Havana using the European R1 channel
of 145.600 , and all use the minus 600 kiloHertz shift. SLIM JIM
antennas built using TV twinlead fitted inside PVC pipes are very rugged
and reliable, and they are also very easy to transport and install,
providing a lot of gain over the typical 2 meters band handie talkie
short vertical antennas that are connected directly to the rig, the so
called rubber duck
or more properly short helically loaded vertical antennas. At my
workshop, the standard procedure for assembling the SLIM JIM takes about
one hour, and the antenna comes out with either a female coaxial
connector at the bottom , or with a length of coaxial cable, usually
about 3 meters or 10 feet to which a male coaxial connector is attached.
The length of the PVC pipe is such that at the bottom of it there is
room to fit a mast U clamp, so the antenna can be easily attached to any
existing pipe mast.
Comparative measurements done between the handie talkie's factory short
antennas and our homebrew SLIM JIM's show that the SLIM JIM provides
anywhere between 6 and up to 10 dB gain over the rubber duck antennas,
depending on how long or how short the rubber duckies are, and to which
part of the 2 meters band they are tuned.
Without any doubt this variation of the J pole antenna, known as the
SLIM JIM, shows better performance than the classic 300 ohm twin lead J
pole, and that's why we are homebrewing them here . Information provided
at the website of Professor L.B.Cebik, that has the URL
www.cebik.com is extremely useful to help you to design a SLIM JIM
antenna for the two meters band. again the URL or W4RNL website is
www.cebik.com, where you will find lots of extremely useful and very
well written as well as easy to understand antenna related information.
.......
QSL on the air, QSL on the air, to all Dxers Unlimited's listeners that
have requested the Hybrid Regenerodyne Homebrew Receiver files via
e-mail... Sorry, but I haven't been able to finish preparing the dot zip
package, mainly because yours truly is not particularly good at doing
computer electronic schematic diagrams... I do need to practice a lot
more, so that the schematic diagrams come out faster... anyway, I think
that before 2006 is over, the dot zip computer file with all the
required information to build the Hybrid Regenerodyne receiver and its
power supply will be finished,and then I will start e-mailing it to all
of you who have requested it. Let me remind you that this is a very
flexible receiver design, aimed at experimenting on all bands from the
AM medium wave broadcast band up to the 6 meters or 50 megaHertz amateur
band. The audio amplifier module and power supply are built on a
separate chassis and are housed inside a nice wooden cabinet that serves
also as the loudspeaker baffle, and this module will work very well also
as a standalone unit for further radio hobby experiments that you may
want to perform in the future.
The radio receiver's radio frequency module and detector are built on a
separate chassis, with the regenerative vacuum tube detector contained
into a very tightly shielded enclosure to prevent leaktrough of signals
at the detector's operating frequency from coming in. The detector's
tuning range is practically
unpopulated during the local daylight hours, but during the evening,
signals in the range from 1.7 to 4.0 megaHertz may leaktrough past the
front end and into the detector, so that's the reason that the detector
has to very extremely well shielded in an enclosure made of
steel if possible, so that it will provide both magnetic and
electrostatic shielding. The regenerative detector's coil of the
prototype was wound on a beautiful ceramic form, that I installed well
removed from the walls of the enclosure, so as to keep the coil's Q as
high as possible.
Si amigos, you may start thinking about the year's 2007
first radio project: Arnie Coro's Hybrid Homebrew Regenerodyne .... send
your request to be included in the HHR receiver's mailing list to
arnie@rhc.cu, again, arnie@rhc.cu, and all information about this and
other regenerative receiver projects will be sent directly to your
e-mail address amigos !!!
Radio is a wonderful hobby, and I can assure you that the unique
experience of listening to a radio that you have built yourself is
something that you have to experience in order to really understand it !!!
......
And now amigos, as always at the end of the show, here is Arnie Coro's
HF plus low band VHF propagation update and forecast. Solar activity is
moving slowly down, and we haven't seen more big solar flares during the
past several days, after the unusual X9 and X6.5 flares generated by
active sunspot region 930.... Solar flux is now around 90 units and
moving down, but, we may see more more class C solar flares during the
next two to three days. Local evening propagation conditions are going
to be good between 3 and 10 megaHertz, but the maximum useable frequency
available to any part of the world from your location is going to drop
dramatically as the sun sets ... And at daybreak, the maximum useable
frequency curve will show a very slow upward swing, because of the low
solar flux prevailing at this moment. An early start of the winter
Sporadic E season may be in progress, so watch for E skip signals on low
band TV stations, channels 2 to 4 in the Americas, and for 10 and 6
meter amateur bands DX anywhere in the northern hemisphere. See you next
Saturday and Sunday UTC days amigos, at the weekend edition of Dxers
Unlimited. Don't forget to send your comments about this program to
arnie@rhc.cu, or VIA AIR MAIL to
Arnie Coro, Radio Havana Cuba, Havana, Cuba
Dxers Unlimited DRM Opinion Poll + answers
and comments
Lots of answers coming in from all over the
world regarding the questions I asked during the most recent mid week
edition of Dxers Unlimited about DRM , Digital Radio Mondiale... and I
will review some of them in detail and add some comments from my own
tests and detailed observations...
.....
Here is now the first part of the results of the opinion poll launched
here during this past mid week edition of Dxers Unlimited about DRM,
Digital Radio Mondiale system.
Let's start with the first statistical analysis of the
answers so far received , all via e-mail , because
replies to the poll sent by AIR MAIL are going to take a little more
time as expected.
Well, so far one hundred and ninety seven e-mail messages received from
twenty three nations and territories, of which one hundred percent, yes,
, all, each and every one of them were critical of the Digital Radio
Mondiale system, and to this I must add, that some of the messages
received contained very angry and well documented comments about how the
present DRM broadcast transmissions are producing heavy interference to
standard analog international short wave broadcast transmissions, an
issue that I think deserves a lot more of attention from the Engineering
Departments of the stations involved in the use of the DRM technology.
Another important fact about the comments coming from listeners from
five continents is that not a single person has been able to find a
commercially built working DRM receiver that can pick up those
broadcasts reliably.
I emphasize reliably, because one of the main objections to the DRM
technology is precisely that it is not reliable for everyday listening
because of its characteristic sudden drop outs, when the sound of
the station you are picking up simply vannishes, and nothing is heard
for a certain period of time... then listeners explain in their e-mail
answers to the poll, that the audio suddenly
comes back with a plop or click sound, and you loose whatever was on the
air during the DRM drop out.
Just to give you an idea of how the replies that came in to arnie@rhc.cu
read, here is an example
From a listener in the US state of Virginia, who is also
a ham radio operator:
Arnie,
1. "Have you ever listened to Digital Radio
Mondiale, DRM broadcast transmissions on short
wave?".
Answer. Yes with receiver, computer and software.
2. "And in case that your answer is yes: again, in
case your answer is yes, give your impressions about
those DRM broadcasts regarding quality and
reliability of reception."
Terrible and useless. Broadcast was Radio Sweden
via Sackville, Canada. So many dropouts and signal
not locking that program was useless. Analog signal
from Sackville, Canada is usually very strong.
As we know a digital signal is either received or
not. There is nothing in between.
We need a new Q code for DRM. I propose QRD (as in
crud. Crud is English slang for rubbish).
DRM also causes hash to analog broadcasts making
analog broadcasts often useless.
Unsure how people will receive DRM broadcasts
without affordable receivers.
And he continues by making a comment that I fully
agree with, regarding the present use of DRM transmissions
If DRM continues, specific out-of-band frequencies
should only be used for DRM.
Signed Kraig, from Virginia
Another answer to the DRM poll came from the United
Kingdom, where listener Alan has experimented with
a very expensive commercial version of a receiver
that is advertised as fully DRM capable. Alan says that
he has very carefully evaluated DRM reception from
different transmitting stations, and notice he makes
a very good reference to transmitting stations , and not
to the program source, something that speaks highly
about the excellent analytical job Alan has done for
more than a year now. He comes forward with a one
sentence opinion that I fully endorse:
Arnie, DRM, Digital Radio Mondiale, is doomed to
failure, because it the technology is simply not good
for short wave broadcasting applications. The drop
outs, those black holes during the reception of
DRM broadcasts are horrible, making the reception
of stations using DRM very annoying to say the least.
Now more about DRM, its problems, difficulties
and its very bad impact on analog short wave broadcasts
that are operating legally near the frequencies of the
DRM transmissions that are generating so much unwanted
interference, that is certainly producing a lot of problems
on the international high frequency broadcast bands
where DRM transmission are taking place on
frequencies adjacent to analog broadcasts.
According to several senior broadcast engineers that
yours truly has asked for opinions about DRM, the
problems of this technology are divided into three
main areas:
One: the technical characteristics of the transmitter
used for DRM and how the actual DRM signal
to be broadcast is adjusted to comply with the
bandwidth regulation in effect on the HF bands
Two: The lack of "memory", that is according to one
of Cuba's most prominent broadcast engineers and
university telecommunications engineering professor
Jorge Inclan Artze, who unfortunately passed away
recently, the DRM technology is fundamentally wrong
for short wave broadcasting, because those who
designed it , according to Inclan and I quote from my
notes of an interview about this topic " they simply
forgot that short wave propagation via the ionosphere
is totally different from the ground wave propagation
used by daytime AM broadcast band and FM broadcast
band stations" And Inclan added that the basic idea
of digital broadcasting is good, but that it must
be combined with sophisticated computer hardware
and software in order to make it a viable and reliable
option. He then asked his wife Aida, to draw for me
some of his ideas, because Inclan had lost his eyesight
many years ago. Aida, also a senior broadcast engineer
drew a block diagram in which the role of a buffer
memory and a redundant transmission of signals
system were integrated so that the extremely annoying
dropouts will simply dissapear if, and they both Inclan
and Aida underscored, if, a time window long enough
to compensate for deep fading was included in the
software that will handle this digital broadcasting
technology that would be capable of dealing with the
typical short wave ionospheric propagation conditions.
Now amigos, another of the answers to the DRM
poll that came from a long time listener in the USA...
And before reading it, let me add that due to the great
impact that this topic has had, I will be continuing to
review it on our upcoming mid week edition, where I
will also repeat the DRM poll's questions for those of you
that have now become interested in this controversial
topic...
Amigo Randall, from the USA, a long time listener wrote
and says: Dear Arnie, DRM in its present form simply
doesn't work...and it is a nuisance to analog signals
that otherwise could be well heard by listeners...
DRM transmissions MUST be entered at the ITU
as experimental, and they MUST be moved away from
the internationally assigned short wave broadcast bands
until the DRM or other new technology that is better
are fully compatible with existing 10 kiloHertz wide
analog A3 Double Side band plus carrier broadcast
transmissions...
More about DRM and your opinions that are reaching
me here from all over the world in upcoming editions
of Dxers Unlimited, and if you want to send your
points of view about DRM, send them to arnie@rhc.cu
of VIA AIR MAIL to Arnie Coro, Radio Havana Cuba
Havana, Cuba
