[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [HCDX] Dxers Unlimited's script for 11/12 December 2007
Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited’s mid week edition for Dec 11-12 2007
By Arnie Coro
Radio amateur CO2KK
Hi amigos radioaficionados around the world and in space… welcome to the
mid week edition of RHC’s twice weekly radio hobby program, featuring
today an update about the recent significant increase in solar activity,
that sent the daily sunspot number up to 42 units, with the
corresponding increase in the daytime maximum useable frequencies .
I am Arnie Coro, radio amateur CO2KK, and as always it is nice to have
the opportunity of sharing with you about 17 minutes of on the air and
on the world wide web time… Here is now item two: A totally portable
loop antenna, that can be assembled and taken down in just a few minutes
can be built using simple construction techniques that can be put in
practice using simple tools. No need for a machine shop for building
this one, that can be transported very easily, because its longest
segment is just 40 centimeters long, so it fits easily into any travel
bag… The use of high quality bolts and wingnuts, allows the fast
assembly of the antenna, that can be made to reach a diameter as small
as one meter or a large as two meters. The one meter diameter loop will
work very nicely from 10 to 30 megaHertz, but its best performance will
show above 15 megaHertz. Likewise, an intermediate size loop, just one
and a half meters in diameter will provide good performance in the range
from 10 to 15 megaHertz… The larger loop allows operating from about 6
to 12 megaHertz, and although it is more difficult to handle, it is
certainly an ideal option for ham radio operators that enjoy backpacking
and other forms of portable operation.
More about the SEGMENTED LOOPS with wingnuts later in this mid week
edition of Dxers Unlimited…
Stand by for a few seconds, I’ll be back after a short break
For station ID…
…………….
This is Radio Havana Cuba, the name of the show is Dxers Unlimited, and
yes we do reply your QSL requests, via e-mail and also VIA AIR MAIL… We
do have now a nice pocket calendar that you can also request via e-mail
or by sending a postcard… Now here is item two in detail. The SEGMENTED
LOOP WITH WINGNUTS, came out as an idea that challenged the usual way of
building magnetic loop antennas. I discussed the effects of the many
contacts that exist when using the segmented loop technology and several
of my local radio engineering gurus said that for receive only antennas,
the losses could be neglected but that the concept needed practical
testing in the case of using this type of antenna for transmitting.
The first one that was built uses wide aluminum angle strips, each 50
centimeters long and with holes drilled at both ends.
The holes are for a 10 mm diameter bolt, and the succesive strips used
to assemble the antenna are kept connected with the 10 milimeters
diameter bolts, starwashers, pressure washers and a wingnut, so it is
very easy to assemble and dismount the antenna…The areas that are joined
have to be cleaned very well with fine sandpaper every time the antenna
is assembled, and I must add that this loop antenna is not intended to
be used as a permanent installation.
At the bottom of the loop the two opposing segments are joined via a
small box where the tuning capacitor is placed.
For receive only applications, the capacitor can be an air spaced
variable removed from an old vacuum tubes radio , but for transmission
one must use a variable capacitor with wide spacing and ceramic or
teflon insulation.
This type of antenna does require constant retuning, because it has a
very narrow bandwidth at resonance, so the usual way of using it is by
placing the antenna as near to the radios as practical. But beware that
when used for transmitting, the antenna generates a very intense near
field radiation, so it should not be used with powers above 25 Watts ,
in order to reduce exposure to electromagnetic radiation.
Homebrewing the SEGMENTED LOOP WITH WINGNUTS, can be accomplished with
standard hand tools and an electric drill … My first prototype took
about three hours to complete, and as a matter of fact the PVC mast that
supports the antenna was more difficult to build than the antenna
itself. For portable outdoors installations the antenna can be hanged
from a tree using dacron or kevlar rope, but you can also take along a
portable mast that can be easily assembled at the site.
My tests using a 10 Watts power output transceiver on the
20 meters band with the wonderful PSK31 digital keyboard to keyboard
mode with the SEGMENTED LOOP WITH WINGNUTS placed on my terrace,
provided two way contacts with stations in 10 countries and three
continents even though solar flux was at rock bottom levels. I then
proceeded to install a compact loaded dipole that is half the size of a
standard 20 meters band half wave dipole, and prepared a switching
arrangement so that the two antennas could be switched back and forth
immediately, so as to be able to compare signals, both when receiving
and when transmitting. The results after many comparative tests showed
that the time spent building the SEGMENTED LOOP WITH WINGNUTS, was worth
every minute of it…My previous experience with the compact dipole for
portable operation had left a very good impression, but the new loop
antenna exceeded all my expectations, with the only inconvenience that
if I wanted to move from the 14.070 kiloHertz PSK31 center frequency to
the SSB voice segment of 20 meters, I had to retune the magnetic loop
tuning capacitor for minimum standing wave ratio when transmitting or
simple for maximum signal when receiving…
Si amigos, yes my friends, oui mes amis… one inch by one inch that is 25
milimeters by 25 milimeters aluminum angle , 10 milimeters bolts and
starwashers, pressure washers and wingnuts , about three hours of your
weekend spare time , a high quality variable capacitor , a coupling loop
made of number 8 copper wire and a length of 50 ohm coaxial connector
for the particular radio you are going to use with the antenna are all
the materials needed to homebrew it…
The complete step by step building instructions with photos are now in
the works, and soon to be completed into a dot pdf file that can be sent
via e-mail, so if you are interested in the possibility of homebrewing
this portable antenna, just send me an e-mail to arnie@xxxxxx, or a
postcard VIA AIR MAIL to Arnie Coro , Radio Havana Cuba, Havana Cuba.
……..
You are listening to the mid week edition of Dxers Unlimited and here is
item three of today’s show…Digital Television Dxing is a new addition to
my list of the many ways one can enjoy our radio hobby… According to
reports from several listeners, Digital TV is much more difficult to
receive at long distances that analog signals, but I have not yet been
able to test Digital TV DX myself, so can’t provide an opinion on this
subject… anyway, the fact is that our hobby continues to develop and to
bring up challenges, like this new one, Digital TV Dxing amigos… Item
four: Just a few days for 2007 to come to its end, and several of the
2008 handbooks editions are now circulating… The two most popular for
short wave listeners are the World Radio and TV Handbook and Passport to
Worldband Radio… I haven’t seen them yet, but I can tell you that buying
one or the two of them is well worth the investment as the editors do
make a big effort to provide the most up to date information for radio
hobbysts.
For amateur radio operators, the Radio Society of Great Britain Radio
Communications Handbook is in my humble opinion an essential consulting
book at every radio amateur station… and certainly a more complete
compilation than the ARRL Radio Handbook.
Item five: Here is LA NUMERO UNO, the most popular section of Dxers
Unlimited… YOU have questions and Arnie tries to answer them as fast as
possible. Today’s first question came from listener Jordan from Canada…
He wants to know how the so called precipitation static can be
overcomed… He explains that when it snows at his location, radio
reception on the short wave bands becomes very difficult and that a
local very experienced radio amateur told him that this was due to a
phenomenon known as “precipitation static”… Well amigo Jordan your ham
radio friend was absolutely right… and it can also happen when it is
raining at a time that the atmosphere is paradoxically with a very low
water content… snow static, and rain static can’t be cleared by any
known method that I know about… You simply must relax and wait until the
noise clears amigo !
The second question came from the United Kingdom, where listener Milton,
who picks up our 11760 kiloHertz frequency during the early morning
local time, wants to know about the relative popularity achieved by the
many different digital communications modes that amateur radio operators
have now access to and are allowed by their telecommunications
administrations to use. Well amigo Milton, without any doubts the PSK31
keyboard to keyboard mode is the most popular one of them all, with more
and more ham radio operators around the world using it… The PSK 31 mode
can be implemented even using old computers and simple to install and
operate software, and after a few QSO’s you can become familiar with it
and its outstanding capability to provide DX communications using very
low power. Other more sophisticated digital modes require more bandwidth
and have so far not become so popular . Digital voice is now making slow
headway , and a recent version of a digital voice mode that uses a less
than one and half kiloHertz bandwith is now undergoing regular testing
by radio amateurs. So far the experiments show that the software used to
encode and decode the voice is good enough to produce practical results,
but it also seems that it does require more polishing on the part of the
software developers as decoding isn’t easy at all and the voices that
come out of the loudspeakers are very, very similar to robots of science
fiction films !
And now amigos, as always at the end of the program , here is our
exclusive and not copyrighted , in the public domain, Arnie Coro’s Dxers
Unlimited’s HF plus low band VHF propagation update and forecast… Solar
activity is hovering between low and very low… There is a very
interesting sunspot emerging from the limb of the solar disk that will
be capturing the attention of solar scientists during the next several
days because of its high solar latitude location. Solar flux was around
85 units and the effective sunspot number at 14 hours UTC Tuesday was
31, sending the daytime maximum useable frequency on North –South
propagation paths up to around 35 megaHertz… Sporadic E openings should
be becoming more frequent as we approach the winter solstice, and that’s
good news for TV and FM broadcast band Dxers as well as 10 and 6 meter
bands amateur radio operators. Hope to have you all listening to the
weekend edition of Dxers Unlimited, Saturday and Sunday UTC days, and
don’t forget to send me an e-mail with your signal reports and comments
about the program, send mail to arnie@xxxxxx or VIA AIR MAIL to Arnie
Coro , Radio Havana Cuba, Havana , Cuba
---[Start Commercial]---------------------
Preorder your WRTH 2007:
http://www.hard-core-dx.com/redirect2.php?id=wrth2007
---[End Commercial]-----------------------
________________________________________
Hard-Core-DX mailing list
Hard-Core-DX@xxxxxxxxxxxxxxxx
http://montreal.kotalampi.com/mailman/listinfo/hard-core-dx
http://www.hard-core-dx.com/
_______________________________________________
THE INFORMATION IN THIS ARTICLE IS FREE. It may be copied, distributed
and/or modified under the conditions set down in the Design Science License
published by Michael Stutz at
http://www.gnu.org/licenses/dsl.html