Dxers Unlimited

Dxers Unlimited 27-28 April 2004

By Arnie Coro

Radio amateur CO2KK




Hi amigos short wave listeners,radio amateurs, TV Dxers, AM broadcast band Dxers, , si, YES, you
radio enthusiasts are now invited to join me for the next seventeen minutes at this mid week edition
of Dxers Unlimited, the radio hobby show for both beginners and experts alike.

I am Arnie Coro, radio amateur CO2KK , your host here in Havana, now ready for item one: listener's
feedback keeps me working the whole week amigos ! Radio hobby related questions, signal reports,
comments about Dxers Unlimited and other Radio Havana Cuba programs is always coming in when I have
my computer connected to the local ISP. and when we go to the Post Office , there is always a whole
stack of Dxers Unlimited's mail waiting . Here is now item two:radio noise is at this moment and
will continue to be in the immediate future our number one problem. The implementation of the so
called BPL technology, that is broadband over the power lines, is the biggest threat ever to the
radio hobby amigos ! But , fortunately, tests are demonstrating that BPL is not a very reliable
technology at all, using the frequency range from 2 to 80 megaHertz as it stands now. So, we may see
this version of BPL just go down the drain, as users realize that it brings them and their neighbors
a lot of headaches !!! Item three: Hurricane season here just a few weeks away, and that's why Cuban
radio amateurs continue their preparations to deal with the half year long tropical storm season
that starts on June the first and ends on November the 30th. Among this year's highlights regarding
emergency preparedness is the installation of several more 2 meter band FM repeaters, located at the
same sites as TV and FM stations , so that they can benefit from the use of standby Diesel
generators and especially reinforced towers, although I must say that when a hurricane comes in ,
even the most well designed and constructed radio and TV towers may be downed by the tremendous high
speed pulsating winds.

Item four: Tips and techniques is becoming increasingly popular among you all amigos, so I will try
to include this section of the show once a week . The Tip for today will be dealing with broken down
amateur transceivers, and some notes on how to try to fix them. ASK ARNIE will be our number FIVE
item here today, and as always , at the end of the show, I will be presenting Dxers Unlimited's HF
propagation update and forecast .

Stay tuned for more radio hobby related information coming to from Havana. I'll be back with you in
few seconds!!!

..

Si amigos ! We do QSL, SURE, and our beautiful QSL cards may form part of your collection very
easily, send me a signal report and comments about the program you hear to arnie@rhc.cu, again
arnie@rhc.cu, or VIA AIR MAIL to Arnie Coro, Radio Havana Cuba,Havana Cuba !!! BPL, broadband
Internet access using the power lines for transmission of the digital information requires sending a
certain number or radio frequency carriers over the AC power lines, so that the encoded digitalized
data can be picked up by connecting a special box to the power line using circuits that will
separate the digital information from the actual 60 Hz power line voltage.

The BIG problem is that no one has found, and I doubt very much it someone can do it, a way to keep
the carrier frequencies within the wires that carry the AC power to each individual home.

In other words, frequencies between a bit less than 2 megaHertz and 80 megaHertz will be radiated
into the vicinity, and I also expect carrier harmonics to appear, extending the frequency range of
the interference well past the 160 megaHertz limit.

As you can imagine, digital signals covering up all the radio frequency spectrum from 2 megaHertz
all the way up to 160 or even 200 megaHertz, will simply make impossible to use other radio
services, including international short wave broadcasting,aircraft long range communications ,
safety systems that operate on the VHF low and VHF hi bands etc. So far several national
telecommunications authorities have banned the use of BPL with the present HF to VHF low band
technology , and they are very seriously considering the possible implementation of a different BPL
system that uses higher frequencies !!!.

Be on the alert about BPL, and if the area where you live is wired up for this system, keep a close
watch about the noise levels generated by the BPL system, and file a complaint with your local
authorities as

early as possible.This may or may not prove to be effective, but my opinion is that as more experts
become aware of the many radio systems that may be disrupted by the BPL installations, we may see
shut downs and possibly the abandoning of that technology in its present form.

..

This is Radio Havana Cuba, the name of the show is Dxers Unlimited, and our mid week edition
continues with TIPS and TECHNIQUES that today will be providing information about both hybrid and
fully solid state amateur radio transceivers that need repair. You may find them at hamfests, garage
sales, sitting on top of shelf at a radio amateur's shack. they are now growing in numbers because
fewer people can be found to repair them than ever before. Another limiting factor for the
proliferation of broken down ham radio transceivers that are not repaired is the high cost of such
repairs, that make it a better choice to buy a new one if you can afford it. Nevertheless, here are
a few tips about these older transceivers that in many cases may put them back to work. First of
all, start taking a detailed visual inspection tour of the rig, using a high intensity light source
and a magnifying glass. It's surprising to see how many of these broken down rigs will give you
immediate clues about what was the reason that they stopped working. Just to put you an example,
recently I had the opportunity to take a look at a Kenwood TS520 rig, one of the most well designed
and rugged transceivers ever produced. The rig's receiver was working quite well, but it won't
transmit. Following the detailed and well illuminated visual inspection procedure, I soon found out
a badly burned final amplifier stage radio frequency choke, and two leaking electrolytic high
voltage capacitors. I changed the two capacitors, and hand wound a radio frequency choke of the
appropriate inductance , it was not a look alike of the original part, but my guess was that it
would work at least on the 40 meters band. The owner of the TS520 had operated the radio into a
badly mismatched antenna system, and that burned the radio frequency choke. the two bad capacitors
in the high voltage power supply showed the typical leakage of such components after more than 20
years of operation. By the way, the TS 520 that had been out of service for several years, is now
back on the air at the home of a disable radio amateur ! Always check the power supplies of these
radios, and be sure that the all solid state rigs are never operated at voltages higher than 14
volts DC, as a matter of fact, it is always a good idea to back the voltage output of the typical
13.8 volts DC power supply and operate the transceiver with about 12.5 volts or so, you will loose a
little power output from those solid state final amplifier transistors, but the rig will certainly
last longer !!!

..

You are tuned to Radio Havana Cuba, on the air via short wave and on the world wide web streaming
audio from www.radiohc.cu... And now here is la numero UNO, number one most popular section of the
show, ASK ARNIE.Today I will be answering two questions, one sent by listener

Raul in Mexico, and the other by listener Michael in Germany. Amigo Raul sent a question to ASK
ARNIE, he wants to know what can be done to reduce the size of a horizontal or vertical antenna to a
minimum, and how much can an antenna be reduced in size and still work more or less properly. Well
amigo Raul, just to give you an example, an antenna for the 40 meter amateur band, in this case a
horizontal dipole, can be cut in size by about 60 percent,that is more than half,and still provide
quite effective performance. The problem is how you do it, so as to keep losses at a minimum. A
combination of both inductive and capacitive loading is the way to go, and I am sending to you via
e-mail one of my most recent antenna designs, a 40 meter dipole that is just 9 meters or just a bit
less than 30 feet. It uses two coils located at halfway of each of the two legs of the antenna, and
four spokes located at the end of each leg to add capacitive loading.

After a lot of testing, I settled with this antenna, as a still smaller, more compact one proved to
be both difficult to tune and had high losses. If you have any doubts about the 9 meters long
compact 40 meter band dipole, just e-mail them to arnie@rhc.cu, and I will be more than happy to
clear any doubts you may have.

Now here is Michael's question, Michael lives in downtown Berlin, and he has to face a typical
problem of people living in cities. Radio frequency noise, in this case coming mostly from electric
vehicles, in other words,streetcars that pick up the energy to operate from overhead lines !!! Sorry
amigo Michael , but there is no cure for such man made interference that comes from poor contacts
between the electric vehicle power pick up and the overhead line. I remember traveling to Matanzas
by means of Cuba's only electric railway, and trying to use my radio during the more than two hours
trip without success due to the noise coming from the wiping contacts between the electric train and
the overhead power line. My advice amigo Michael is for you to obtain a fast acting gating audio
filter, that may help to reduce the noise bursts coming from the streetcars !!!

...

And now amigos, as always at the end of the show, here is our exclusive Dxers Unlimited's HF plus
low band VHF propagation update and forecast. First sporadic E openings already happening and that's
good news for 6 meter band radio amateur operators, TV Dxers and FM band Dxers. So far I have seen
the maximum useable frequency supported by a sporadic E cloud go past 50 megaHertz , something that
made possible copying several beacons on that band.

Solar flux is now hovering around 100 units, and there is one active sunspot group, number 599 that
according to scientists has enough energy to produce M type solar flares during the next several
days. My own monitoring of the 19 meters international broadcast band Sunday evening my local time,
showed several strong signals , indicating quite good propagation. Be on the lookout for signs of
the typical rising

Maximum useable frequency curve, associated with Sporadic E events, and if you are a radio amateur,
start calling CQ as soon as possible when this happens, and you will be pleasantly surprised to make
some nice two way contacts. See you all at the weekend edition of the program amigos !!! And don't
forget to take a little time and send me your signal reports, comments about the show and radio
hobby related questions to arnie@rhc.cu or VIA AIR MAIL , a postcard will be fine. mail to Arnie
Coro, Radio Havana Cuba, Havana, Cuba