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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


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