Re: [HCDX] Dxers Unlimited's mid week edition for 26-27 December 2006

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

Here is today's script of Dxers Unlimited

Radio Havana Cuba

Dxers Unlimited

Dxers Unlimited's mid week edition for 26-27 December 2006

By Arnie Coro

radio amateur CO2KK

Hi amigos radioaficionados... Seasons Greetings and a Happy New Year 
2007 to you all... I am Arnie Coro, radio amateur CO2KK, your friend in 
Havana and host of this twice weekly radio hobby program that tries to 
deal with every aspect of our wonderful way of enjoy our spare time... 
from winding a modulation transformer required to restore an antique 
transmitter, to the how to improve your 2 meter band handie talkie 
coverage during an emergency using readily available materials... from 
learning how to make your own HF propagation forecasts to teaching 
newcomers to the hobby the basics of radio communications 
technologies... YES AMIGOS, Dxers Unlimited's success is based not only 
in its coverage of a really widespread number of issues, but also by 
providing critical analysis of radio developments, like what we have 
been doing recently regarding the controversial DRM transmissions, that 
I agree with many listeners that wrote to me, can also be extended to the
IBOC or In Band On Channel transmission system for the
AM broadcast band too... About IBOC for FM I won't
comment yet, as it does require a very comprehensive
study of such a system in order to be able to voice
a well documented opinion. As regards to the short wave
DRM technology now in use , my opinion can be summarized in two aspects: 
One, the transmitters used for broadcasting DRM short wave signals are 
evidently not well suited for operating on that mode, and Two: the lack 
of receivers in general, and of at least medium priced receivers in 
particular is making DRM a quite
useless effort, and for station managers a real waste
of their budgets ....

More radio hobby related topics in a few seconds, when
Dxers Unlimited's mid week edition continues...

I am Arnie Coro in Havana

.......

Happy hams all along the Cuban archipelago, because
the number of people that passed the amateur radio
license test during the weekend was really impressive.
One of the reasons of the very high number of high
marks has to do with the excellent textbook that
was written and printed after the last National Convention of the Cuban 
Radio Amateurs Federation and the creation at each Radio Club of a 
teaching committee that took the task of giving classes to the newcomers 
to the hobby, so that they will be able to succesfully pass the test. 
For third class licensees, the Morse Code test
is now non excluding as it used to be... it just adds or
subtracts a few points to the overall test mark...
For all class of licenses the top speed required now is
just 5 words per minute, and my personal impression is that in the near 
future the ham radio exams will simply
drop the Morse code, and ask you more digital computer
modes related questions...

Item four: Low sunspot count doesn't mean good AM
broadcast band propagation as some people may think...
You may be seeing an almost zero sunspot count while
a high speed solar wind stream is impacting the Earth,
producing a lot of ionospheric noise and even a
magnetic storm... Item five: Just fixed a defective
Kenwood FM 2 meter band transceiver... and I don't
really know yet where the problem was located... The
"fix" consisted in going trough each and every soldering
point of the rig with high quality low melting point solder
and a lot of patience... The "repair" was suggested by
a website that provides information about the repair
of amateur radio equipment... So, if you find a broken
down Kenwood FM 2 meter band transceiver of
between 1990 and the year 2000, chances are that its
defect may be identical, poor soldering connections
especially at the ones that link one side of the printed
circuit board to the other side...After the soldering
session that took more than an hour and a half, the
rig came back to like with excellent sensitivity , and
also with full power output... so far, after two weeks
have passed, the radio continues to work nicely, so
it was obvious that no component was actually damaged
or out of parameters, just poor quality control at the
factory that allowed those units to escape despite a
soldering machine problem...

.....

Si amigos, we do QSL, and we do reply your radio
hobby related questions, no matter how difficult that
may seem to you and to us too... ASK Arnie is the
section of Dxers Unlimited, devoted to answering your
questions , like this one sent by listener David from
the Upper Michigan Peninsula... Dave asks Arnie
what can be done to remove the static electricity
that accumulates on his wire antenna , especially
during very dry and windy days... Well amigo David,
if your antenna is just used for receiving, it's very
easy to solve the problem by installing two carbon
resistors of about two thousand ohms each in
parallel, and then connecting them between the
antenna and ground... The resistors will act as a
permanent path to ground that will bleed off the
static so that it will never reach a high voltage...
If your antenna is used for transmitting then it is another different 
story, because you will need a special device
that is installed between the transmitter and the
antenna, and is also connected to ground. This device
has the property of ionizing the gas inside it after
a certain critical voltage level is reached, so you
must use the proper one according to your transmitter 's output power... 
I prefer to use a carefully calibrated
spark gap between the antenna and ground... Because
that one I can monitor easily , something that can't be done with the 
gas discharge protection devices...
For all practical purposes there are two approaches
when dealing with static electricity building up...
One is to keep the antenna permanently connected
to a ground systemwhen not in use, and the other is
to when the antenna is in use, keep discharge resistors
of gas discharge devices connected to ground.
Not too long ago I was asked by a local radio amateur
to take a look at his HF transceiver that had loosed
a lot of sensitivity.... and all we found was a dead
MOS FET input amplifying device, possible due to
a local thundertorm, as my friend recalls that after
the storm the radio had lost it usually very good ears !!!
It took about an hour to change the radio frequency
amplifier and readjust the front end a bit... By the way
there are many somewhat old, but certainly still in
good condition to restore back to full operational
capabilities hanging around all around the world, as
the "art" of fixing electronic equipment is now something
of a lost thing of the past, as no one even attempts anymore to fix 
those radios because the extremely high
cost of specialized labor... After a four or five hours long
repair job, you may be charged for labor more than
the actual cost of a new rig !!! And amigos, I am not
kidding !!! I have received many e-mail message
and letters asking what to do with broken down
receivers and transceivers in need of repair, as th
cost seems to be astronomical...

....

Antenna, antennas, without antennas, radio won't
exist, and every day someone seems to come out
with a new idea on how to design a new antenna
system... Some of those ideas are esoteric and
meaningless, like the now ill fated CFA or Crossed
Field Antenna, that seems to be more of a scam
than anything else. But also from time to time
someone comes out with a good idea, or a modification to an already 
existing antenna... One of the best examples
is the FOLDED GROUNDED MONOPOLE,that is
so succesfully used nowadays by AM broadcast band
stations to replace the series fed isolated from ground
vertical radiators. Using the folded grounded monopole
has many advantages for the AM stations, among the
the fact that damages from lightning strikes are much
less , and also that they can now rent tower space to
other users of the radio frequency spectrum , like
cell phone systems and microwave relays.
Radio amateurs have been very slow in picking up the
idea of the folded grounded monopole vertical, despite
the fact that it is very easy to implement, and provides
nice bandwidth. As a matter of fact, AM stations have
converted existing antennas to the folded monopole
with very little investment and in a very short time.
Here in Cuba many AM broadcast stations are succesfully
using the folded grounded vertical monopole antenna
and some of them are operating with diplexers, feedin
two transmitters on different frequencies  to the same
antenna system, something that saves a lot of resources.
......

Dxers Unlimited's mid week edition continues now
with more comments from listeners about the terrible
effects of poorly adjusted DRM transmissions...
According to several reports received here, signals
up to thirty, yes you heard it right, thirty , three zero
kiloHertz wide have been reported on some of the
DRM transmissions, making reception of stations
located up to thirty five kilohertz away from the
poorly adjusted DRM broadcast very difficult indeed.
I think it is up to the telecommunications authorities
of the nations where the affected stations are located
to file up the corresponding complaints to the offending
broadcaster's telecomms administration, so that
approppriate action can be taken.
Discussing this excessive bandwidth problem with
one of Cuba's top most broadcasting engineers, he
told me that , in his opinion, had to do with the fact
that the DRM technology requires that the transmitter
be capable of a very high degree of linearity, and at
the same time be able to manage a very wide margin
of peak to average power ratio. He then added that
old transmitters used for standard AM type broadcasting
are certainly not capable of handling the DRM
requirements... If you , as a regular listener of
short wave broadcasts hear a rush type noise that
seems to blanket your favorite station reception,
be almost sure that a DRM transmission is taking place
nearby without due regard and respect for your
station from the broadcaster using DRM. If  you notice
this kind of problem, send an e-mail to arnie@xxxxxx
Now, 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 at very low level, but two small sunspot
are now in sight, after days with a spotless Sun,
solar flux hovering around 75 units, and the A index
has moved down now... after the solar wind speed
has diminished. Good chances for VHF E skip openings
during the next two weeks , so keep watch on the
low band TV channels where they are available, and
on the amateur bands, watch for very short skip on
twenty meters, as both are good indicators of ongoing
Sporadic E openings... Send me your signal reports
and comments about the program to arnie@xxxxxx
or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba
Havana, Cuba

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