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Re: [HCDX] Dxers Unlimited's script for 8-9 September 2007
Dxers.. Unlimited
Dxers Unlimited’s weekend edition for Sept 8 -9 2007
By Arnie Coro
Radio amateur CO2KK
Hi amigos radioaficionados ! Equinoctial propagation just about to be in
full swing all around the world , and lots of Dxers Unlimited’s
listeners are already enjoying it according to the reports that I am
receiving at my e-mail address, arnie@xxxxxx… Several experienced
amateur radio operators say that even the slight propagation
disturbances of the past several days have helped in a way, by providing
some unique contacts from stations not normally heard on some bands.
Ionospheric absorption is also rather low, precisely due to the rock
bottom low solar activity prevailing during the past several days and
that helps too…
Item two: QSL on the air to the many Dxers Unlimited’s listeners that
send questions to my program. YES, there is a cue or waiting line of
sorts, but I have found out that many questions are quite similar and
that helps to answer them on the air to many listeners at the same
time.. Perhaps the wording was a little different but the essence of the
question is the same… That explains why in some programs I make
reference to questions sent in by listeners in several countries… Item
three: Talking about questions, a ham radio operator asked recently
while we were in a two way SSB contact on the 20 meters band what he
could gain by changing his three element monobander , replacing it by a
13 element log periodic array. He was quite shocked when I said that on
the 20 meters band he would gain absolutely nothing !!! Then , the
lengthy explanation about how the log periodic arrays really work
followed, and my Canadian friend found out that a typical log periodic
Yagi array for the HF bands provides the operator with what could best
be described as an almost infinite number of three element Yagis from
the lower cutoff frequency to the antenna’s highest possible operating
frequency… More about the very interesting wide band log periodics in
today’s Dxers Unlimited’s antenna topics section.
Item four: My CW key here is a retired computer mouse… yes, I heard that
on the popular 30 meters CW amateur band the other day… and I was really
happy when the operator sending that explanation about his CW key added
that he got the idea by listening a few years ago to Radio Havana
Cuba’s Dxers Unlimited’s program… As you can guess amigos, that
literally “” made my day “”…
Today we will also feature our most popular section of the show, YOU
HAVE QUESTIONS, and Arnie tries to answer them, and as always at the end
of the program, our exclusive and not copyrighted HF plus low band VHF
propagation update and forecast.
Stay tuned for more radio hobby related information, right on this same
frequency or web connection. I am Arnie Coro in Havana, back with you in
a few seconds.
…..
Si amigos, sure, playing with antennas is one of the 81 ways you and I
enjoy playing with our radios… and here is our ANTENNA TOPICS section,
today devoted to a particular antenna, a very special one indeed that
has become the mainstay of many HF communications systems and that is
also finding use among the world’s international short wave
broadcasters… I am talking about the LOG PERIODIC YAGI antenna array…
The LOG PERIODIC YAGI is certainly a beautiful looking antenna, and for
those needing instant frequency changes trough a given range , the LOG
PERIODIC is an ideal antenna indeed. LOG PERIODIC antennas for the range
between 10 and 30 megaHertz are now quite popular, but you will also
find much larger versions designed to operate from 6 to 22 megaHertz,
especifically targeted for international broadcast stations use.
Amateur radio operators with a very affluent budget have also benefitted
from the log periodics, but in my opinion, they are not really worth the
investment for ham radio use. A 10 to 30 megaHertz LOG PERIODIC is a
really large antenna by all standards, and that’s why some antenna
manufacturers are offering a somewhat smaller version for operating
above 20 meters, that is , an antenna with its lower frequency limit set
at 13 megahertz and its upper frequency limit at 30 megaHertz.The size
of such 13 to 30 megaHertz LOG PERIODICS is much more manageable for a
typical amateur radio installation, and such antennas may have from 7 to
15 elements, with the ones with more elements offering better performance.
A 13 to 30 megaHertz log periodic YAGI will provide the operator with
the possibility of operating on the 20, 17, 15, 12 and 10 meter bands,
so it is a 5 band antenna for ham radio, plus an excellent receiving
antenna for short wave listening on the 22, 19, 16, 13 and 11 meters
international short wave broadcast bands. And of course that the user
can also pick up many communications services, the so called utilities
that operate using that range of frequencies.
A 13 to 30 megaHertz LOG PERIODIC antenna for your amateur radio station
is certainly an expensive antenna if you build it properly, and it does
require a heavy tower and a heavy duty antenna rotor to handle it.
Now, for the real world gain figures… the typical LOG PERIODIC is more
or less the equivalent of a three element YAGI array on any frequency
all along its operating range…You may read some absurd claims from
antenna manufacturers, but all tests and computer modelling will take
you to the same ballpark figures, about 6 to 7 dB gain over a half wave
dipole…
Log periodic antennas for VHF and UHF frequencies are another different
story, as size is not then a limitation, and the designer can look for
more gain without having to worry about mechanical considerations.
One of my favorite TV and FM band Dxing antennas is a 13 element wire
LOG PERIODIC designed to operate from 50 to 200 megaHertz, a four to one
frequency ratio. It’s a nice looking antenna, it’s lightweight so I
have also used to operate a portable station on the 6 and 2 meters
amateur bands. You can learn a lot about LOG PERIODIC ANTENNAS by
running a search on one of the popular Internet search engines and
downloading some of the very interesting scientific and technical papers
available on the web about these antennas, or you can also go directly
to my good friend’s Dr. L.B. Cebik website and look for his authorized
opinions about the log periodics… the URL is www.cebik.com, again,
www.cebik.com, and I am sure that you will really enjoy visiting that
unique site amigos !
……
This is Radio Havana Cuba, the name of the show is Dxers Unlimited, and
here is now our popular, la numero uno !!! You have questions and you
make me work hard to answer them amigos !!! Today’s question was sent by
several listeners in the USA, Mexico, Jamaica and Canada.
They all want to know what is the lower power of radio frequency energy
that will make possible a two way radio contact via the ionosphere… In
other words, what’s the known minimum power that will bounce back to
Earth from the ionosphere. ANSWER: According to accounts by well known
QRP or low power amateur radio operators, powers as low as microWatts or
millionths of a Watt of power.
When HF propagation conditions are at their best, with minimum
ionospheric absorption and low noise levels, radio amateur QRP or very
low power rigs running 5 Watts or less are able to sustain excellent two
way contacts. Reducing power to the 1 Watt level increases the
challenge, and that’s exactly what many of us, QRP operators do, in
order to really test our antennas and receivers , and of course our
operating skills… Going down the MILLIWATT or thousands of a Watt level
is a greater challenge… but let me say that there are now several radio
amateurs that have worked more than 100 Dx entitities using powers in
the 100 milliWatt range. With such low power levels, you do need very
good antennas, an excellent receiver and last but not least, good
propagation conditions.
My 2 Watt power output 40 meter band CW rig is a good example of what I
am talking about… running that rig on the 7 megaHertz or 40 meters
amateur band is very enjoyable, as that part of the short wave spectrum
provides unique propagation conditions at certain times of the day that
make possible excellent two way contacts while running low power. So
amigos who asked, there you are, powers as low as millionths of a Watt
do propagate using the ionosphere as a turn around point, but more
typically powers around 1 Watt or so are considered the lower practical
limit for HF ionospheric communications .
…..
You are listening to the weekend edition of Dxers Unlimited coming to
you from Havana amigos… you can get in touch with us by sending an
e-mail signal report and comments about the program directly to
arnie@xxxxxx, or VIA AIR MAIL, a postcard will be OK and cheaper too,
just send me your postcard report to Arnie Coro, Radio Havana Cuba,
Havana, Cuba, and I’ll be very happy to QSL back to you , so please
don’t forget to send your postal mailing address with your e-mail
messages… Now Dxers Unlimited continues with TIPS and TECHNNIQUES a new
section of the program that is on the air today for the first time:
Todays’ TIP… how to select the best possible headphones for your short
wave radio… By all means avoid the HI FI headphones, you don’t really
need and don’t want wide band audio reproduction when listening to short
wave signals… The best headphones for listening to HF radio are the ones
used by aircraft pilots that are specifically designed to optimize voice
communications.. Sure, I agree, they are quite expensive, but they do
last a very loooong life.
You can find information about aircraft type communications headsets at
any aviation supply dealer…again, they will be expensive, but you will
also get a nice high quality noise cancelling microphone that forms part
of the headset, so that you will be able to use it with your amateur
radio station too… and this was our TIPS and TECHNNIQUES section of
Dxers Unlimited today amigos..
And now , just before going QRT, here is our exclusive and not
copyrighted HF propagation update and forecast… Sunspot number standing
now ZERO, yes you heard it right, it can’t go lower, its ZERO sunspot
count and the solar flux is also at rock bottom level of 67 units, and
for your information scientists consider a totally quiet Sun radiating
65 flux units … No data from the farside of the Sun available so it is
difficult to know what is going to happen in the next few days but
despite those ugly numbers during the rest of the week I see rather
good propagation conditions on the HF bands, something you can find out
by monitoring the bands , especially during the sunrise and sunset
periods, local time. Be on the lookout for some nice DX on the 60 meters
Tropical Band, where you can now find Radio Rebelde’s 5025 kiloHertz
transmitter that is on the air 24 hours a day. See you all at the
weekend edition of Dxers Unlimited amigos, and don’t forget that your
e-mail messages , postcards and letters are really important to keep the
show as useful to radio hobbysts as possible… send mail to arnie@xxxxxx
or VIA AIR MAIL to Arnie Coro , Radio Havana Cuba, Havana, Cuba
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