Dxers Unlimited
Dxers Unlimited mid week edition for 2-3 September 2003

By Arnie Coro

Radio amateur CO2KK




Hi mis amigos radioaficionados around the world, listening on the HF or via our web streaming audio.
This is the mid week edition of your favorite radio hobby program, coming to you from Havana. I am
Arnie Coro, radio amateur CO2KK , and here is item one for today... September is here, and we should
see lots of interesting propagation events during the next four weeks !!! As the autoumn equinox
approaches here in our Northern Hemisphere, the spring equinox will also be nearer down under, and
for a brief period the whole planet Earth will be receiving an almost equal amount of solar
radiation, leading to what propagation experts describe as equinoctial propagation conditions. Yes
amigos, twice every year we radio enthusiasts enjoy a few weeks of very interesting propagation
conditions and we are now just entering that period, so be on the lookout for nice DX especially
around your local sunset and local sunrise periods.... Item two:11760 kiloHertz now on the air in
English from 05 to 07 UTC. This is a test transmission so reports are most appreciated, send them to
arnie@rhc.cu, again arnie@rhc.cu... Item three: A very clever noise cancelling system can be
assembled from passive components... the system requires the use of two antennas, one to pick up the
maximum local noise possible, and the other one to try to pick up the wanted signals... Phasing the
noise signals properly will produce a certain degree of noise cancellation, sometimes enough as to
make reception of some stations possible, despite the very high local radio noise levels. There are
several designs of passive noise cancelling systems available, and all I can say that even a rather
simple one I built here recently, when adjusted with patience, did reduce the local noise level
significantly , especially around the 60 meter Tropical Band, where you can pick up Radio Rebelde's
5025 kiloHertz station, Cuba's only Tropical band broadcast..... Item four : TV DX season, well TV
DX sporadic E season is now over, but we enter into a very interesting season for TV DXERS... the
tropospheric ducting conditions are now starting in areas of the Northern Hemisphere, where the
weather patterns change at this time of the year... So have your TV Dxing setup ready, and keep a
special watch on your weather maps.... Tropo Ducting is weather related, so you can actually make
very good forecasts by watching the weather maps and learning how to interpret them !!! Item five:
Yes its very popular, and listeners tell me they like it a lot... ASK ARNIE, will answer today three
questions sent in by Dxers Unlimited's listeners, and as always at the end of the show... Our
exclusive and not copyrighted HF propagation forecast will provide you with practical tips on how to
optimize your short wave listening and , or, amateur radio activities... Margarita Delgado is my
sound engineer , I am Arnie Coro in Havana, back with you in a few seconds amigos ... stay tuned to
our short wave signals or connected to our streaming audio !!!

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You are tuned or connected to the English language service of Radio Havana Cuba, this is Dxers
Unlimited's mid week edition and here is ASK ARNIE, our popular section of the program devoted to
answering radio hobby related questions to listeners all around the world.. Today's question one:
Comes from California, listener Frank near Los Angeles, wants to know if it is good practice to
change all electrolytic capacitors of vintage electronics before putting the equipment in service...
Well amigo, that's the way to go if you can afford it, have the right replacement capacitors at
hand, and happen to have the time to do job !!! Yes, it is a lot safer to just remove the old
electrolytics , the capacitors that are most likely to fail on a re-start up of old radio gear... As
I said, it will take a lot of time to do it, but the time spent is really worth every second of
it... Having ALL the capacitors changed with fully tested and properly re-formed before installing
new ones will prolong the life of the equipment that you want to restore... BUT the electrolytics
are not the only cause of problems when restoring antique electronics... I have found that bypass
capacitors , especially the ones connected to the high voltage B plus are likely to fail on a
re-start after the equipment has seen years of inactivity... As a good friend of mine that
specializes in restoring antique radios likes to say... it's always good practice to also change ALL
the paper bypass capacitors... And to have fun later testing each one of them individually with a
capacitor tester or a Resistance , Capacitance and Inductance bridge... Guido, my friend says that
it is quite interesting to test for the tangent of Delta of the capacitors, the angle of the
dielectric loss... He recently showed me a plastic bin full of paper bypass capacitors he had
removed from a Hallicrafters SX 25 Receiver he was restoring... He had carefully tested each of them
with the bridge,and each capacitor was in a small envelope with the full data of the test results...
Sure, not a single one was up to the minimum parameters required, especially regarding the high
voltage leakage test that Guido runs on all capacitors, even the brand new ones to be installed as
replacements on the antique gear. Arnie, he said, more than once even a brand new high quality
polyester bypass capacitor has shown leakage currents high enough to just throw it away !!! So amigo
from California, the answer is yes, and not only for electrolytics, also paper bypass capacitors
should be totally replaced when doing a well done restoration project. After all you want your
revived radio to sound good for a loooonnng time !!! Question number two coming to you after a short
break ...

......

Si amigos, this is the mid week edition of Dxers Unlimited, and here is ASK ARNIE , part two: the
question was sent by several listeners, and I am going to answer to all of them simultaneously...
QUESTION: Arnie, is it true or not that reception conditions on the HF bands were better thirty or
forty years ago ??? Well, there seems to be some kind of long winded thread going on at several
short wave listening and ham radio e-mail reflectors regarding this particular topic... After
searching around for historical data, the answer is that every time a solar cycle starts going on
its downward slope, propagation conditions take a turn for the worse, and paradoxically, part of the
downward slope is actually worse than the very last months of the cycle.... This is due to the fact
that geomagnetic storms caused by solar events like coronal holes and flares do happen more
frequently at a certain phase of the solar cycle that happens to come after the peak has passed.....
My forecast for the year 2004 for example, calls for much more stable propagation conditions than
what we have seen during the whole of 2003..... Question number three: Sent by listener Adam in
Barbados, he wants to know if locating his receiving station right next to the shore line will
improve his radio reception... and the answer amigo Adam is YES, no doubt about that... if you can
find a location right next to the ocean, your reception of AM medium wave band signals will be much
better than when you are inland... And short wave reception will also be better as your noise
sources will be only half as when you are completely sorrounded by land... Amateur radio operators
that operate during contests , have learned that placing their HF antennas right at the beach, with
the ground radials into the water provides a significant enhancement of both received and
transmitted signals... Another bit of information that will help you decide for the seaside property
is the fact that the conductivity of the earth near the ocean tends to be much higher than inland...
!!! That's why those that like to enjoy AM or Long Wave broadcast Dxing travel sometimes hundreds of
miles to set up a special DX expedition station right next to the ocean, in order to be able to pick
up DX stations that can simply never be heard far inland... Hope this helps you amigo Adam, and as
soon as you move in to your new property, write again and tell me about the reception you are
getting there !!!..

AH ! That's good, time to answer a fourth question: The next one on the cue came from Canada, where
Dxers Unlimited has lots of fans, like my good friend and regular listener Bruce Atchinson VE6XTC...
well the question came from British Columbia, listener Al asks if he can adapt a microphone
originally to be used with a computer sound card to a homebrew transceiver he is building...Well
amigo Al, you must remember that some of those computer microphones have not one, but two microphone
elements inside, each one feeding a stereo channel... Find out if your mike is stereo by testing it
on a stereo audio amplifier, putting the volume of one channel down to zero and listening. If you
still get audio output , the microphone is a stereo unit, and for your ham radio application you
will need to connect only one of the two elements... By the way one of the cheapest and most
effective microphones that I have tested here are the ones that are used for wireless telephone
handsets... The old wireless phones that are discarded will provide you with lots of nice electronic
components, including a good for voice work microphone that can be easily removed from the handset.
These are usually electret microphones that require a permanent DC voltage applied to their built in
impedance converter unit, that changes the very high impedance of the electret device into the low
impedance that the typical audio pre-amp can handle....

And now amigos , at the end of the show , as always here is Arnie Coro's Dxers Unlimited's in the
public domain , free for all radio hobbysts around the world, HF propagation forecast... and YES,
today I am not providing a Low Band VHF propagation forecast , because the probabilities of openings
between 30 and 60 megaHertz are extremely low at this moment, something I expect to be changing in
about 2 weeks, when the Trans Equatorial Scatter season will be starting... Well here is the 3 to 30
megaHertz data: Noise levels in the 3 to 10 megaHertz range will continue to be rather high due to
tropical thunderstorm activity . The daily MUF peak, the maximum useable frequency to the best
possible DX location will be limited to around 22 megaHertz , with possible very brief periods when
the MUF via the F2 layer may reach up to 30 megaHertz... Solar flux will be around 110 units, and
the effective sunspot number will continue to go down during the next several days...Nightime
reception of short wave broadcasts will be best between 9 and 16 megaHertz, as the 6 and 7 megaHertz
bands will have to face rather high noise levels due to atmospherics... Send your best loggings and
share them with other Dxers Unlimited's listeners around the world, but remember that what may be
heard very well at one location, may prove to be impossible to pick up at other site... send your
reports to arnie@rhc.cu, and don't forget to include your home postal address so that we can send
you our QSL card, verifying your reception of Radio Havana Cuba amigos... See you next Saturday and
Sunday UTC at the weekend edition of Dxers Unlimited ...