Re: [HCDX] Dxers Unlimited's weekend edition for 26-27 May 2007

["Prof. Arnaldo Coro Antich" <inforhc@xxxxxxx>]

Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited’s week end edition for 26-27 May 2007
Hi amigos radioaficionados , around the world and in space… I am 
Arnaldo, Arnie, Coro, radio amateur CO2KK your host at this twice RHC 
program devoted entirely to the promotion and development of our 
wonderful and fascinating hobby, the ever changing and always 
challenging RADIO.
Let’s begin this program with a news item about the forecasting of 
magnetic storm, in my opinion  a very significant breakthrough in solar 
physics and the vitally important relation of our homus sapiens species 
with the Solar System…
A scientist using the Solar and Heliospheric Observatory (SOHO) has 
found a way to forecast solar radiation storms. The new method offers as 
much as one hour advance warning, giving astronauts’ time to seek 
shelter and also ground controllers time to safeguard their satellites 
when a storm is approaching.
As many of Dxers Unlimited listeners have heard here, more than one 
telecommunications satellite has died when a strong magnetic storm has 
sent heavy ions into the critical areas of the spacecraft, damaging 
vital control circuits.

"Solar radiation storms are notoriously difficult to predict—they often 
take us by surprise," says physicist Arik Posner who developed the 
technique. "But now we've found a way to anticipate these events.", he 
added in a Friday press release.
Posner is a member of the research staff of the Southwest Research 
Institute in San Antonio, Texas USA and he also works at NASA 
Headquarters in Washington, DC. His study, titled “Up to one-Hour 
Forecasting of Radiation Hazards from Solar Energetic Ion Events” is 
published in the specialized scientific journal Space Weather.
The early warning of magnetic storms will also provide some interesting 
possibilities for amateur radio operators at high latitudes, as they may 
get ready to make some nice DX contacts via aurora borealis propagation 
that is usually associated with the solar magnetic storms.
Item two: Also related to solar activity… once again after a brief, 
really short period of enhanced activity, the Sun is back to the typical 
levels of solar flux that are experienced during solar cycle minimum… 
Flux levels of around 70 units, very close to the minimum baseline 
activity are now in progress.
Item three: The very low solar activity combined with the summer thermal 
expansion of the ionosphere has sent the daytime maximum useable 
frequency curve as low as it can go… and again, we are watching how once 
the Sun sets, a very interesting increase in the maximum useable 
frequency on some circuits takes place, providing a relatively short 
period of enhanced propagation conditions.
Item four:  Still another compact antenna is making headlines, the 
TAK-TENNA a dipole, makes use of two spiral wound loading coils at the 
ends of the very short elements, providing both inductive and capacitive 
loading…More about the TAK-TENNA in this weekend edition of Dxers 
Unlimited that will continue in a few seconds, after a short station ID…
I am Arnie Coro in Havana…
…….
This is Radio Havana Cuba, the name of the show is Dxers Unlimited and 
you can pick it up twice in the week, on Tuesdays and Wednesdays , our 
mid week edition, and on Saturdays and Sundays our weekend edition, the 
one you are listening to at this moment… Now, as promised earlier, here 
are some comments about the latest newcomer to the long list of amateur 
radio compact antennas, the TAK –TENNA, that uses a time proven and 
effective way of making a very short antenna that is still able to 
provide a rather reasonable radiation efficiency. The TAK-TENNA consists 
of a heavy and well built center insulator, two short braces made of 
aluminum tubing and at the ends of each of them a wire spiral that acts 
as an inductive and capacitive loading that makes the very short antenna 
resonate to the amateur band for which it is designed. The 40 meter 
model is so compact that it can be installed in a very small space, 
making possible to operate on that band that has become much more 
popular now that the solar cycle is at its very bottom. In order to 
better understand how it works, I built from scratch a 10 meter band 
model of the TAK-Tenna, using PVC pipe cross braces to keep the one 
quarter wavelength of wire spirals in position. The antenna is amazingly 
small, and it was possible to adjust it with the standing wave ratio 
meter for resonance on 28.4 megaHertz, while obtaining a rather nice low 
SWR from 28.0 to 28.8 megaHertz . Finding the correct setting for the 
wires that connect the aluminum legs of the antenna to the wire spirals 
wasn’t easy, but finally I ended up finding the right spot.
I used number 14 bare copper wire for the spirals that were
made with a total length of two and a half meters wound into a spiral 
with a diameter of 50 centimeters. Another experiment used a still 
smaller diameter spiral, but keeping the same quarter wavelength of wire 
to form the spiral.
As with any half wave resonant dipole antenna, the TAK-TENNA proved to 
have a rather sharp bi-directional horizontal pattern, so it was very 
easy to find a setting of the antenna that produced the minimum noise 
from my next door neighbors extremely noisy computer an monitor, 
something that could not be done with a fixed half wave wire dipole. 
Now, I must look for the proper materials, and build a pair of these 
antennas, one for 10 meters and the other one for the number one 
favorite DX band, 20 meters,
Before I forget, I used a simple coaxial cable choke balun right at the 
feed point and had no problems with parasitic RF currents at power 
levels of up to 200 Watts.
Small antennas are always coming into the attention of radio amateur 
magazine editors because for HF operation the size of the antenna is a 
limiting factor for many operators that can not work on HF with standard 
size antennas.
………..

ASK ARNIE, si, amigos, sure, you can send your radio hobby related 
questions to ASK ARNIE, la numero uno , the most popular section of 
Dxers Unlimited… Here is today’s question sent to ASK ARNIE, by listener 
Gabriel in Delaware , USA, and also answering a very similar question 
that came from Desmond in the UK… So amigo Gabe and Des, here is the 
question followed by my answer: Question… Arnie can you recommend a 
particular antenna design for someone that has a very small space 
available to install a short wave receiving and transmitting antenna? 
ANSWER: Amigos Gabe and Des my advice is to review the possibilities of 
using , for example, a flagpole antenna if it is possible to install a 
flagpole at your QTHs… A second option would be to explore the use of a 
compact short antenna that uses efficient loading, and a third one , 
that is becoming more and popular around the world, would be to use a 
magnetic loop antenna, that in the case of a receive only installation 
is very easy to homebrew, will cost practically nothing and also will 
prove to be highly effective in making better reception possible in high 
man made noise areas. The problem with a magnetic loop capable of 
transmitting is the extremely high voltages that even a low power 
transmitter will generate in the form of single or two turn coil type 
antennas, which can reach several thousand volts!!!
I regularly used with my bedside HF regenerative receiver an untuned 
short inverted L antenna, that provides very good reception on 
frequencies between 2 and 18 megaHertz, while at the same time making 
possible to listen to local and semi-local AM medium wave band broadcast 
stations.
The short inverted L is an option that may also be considered, and with 
a ground counterpoise it can be used for transmitting on the amateur 
bands from 10 megaHertz up, although its performance won’t be amazing as 
you can expect from a length of wire that is less than a quarter 
wavelength on the 30 meters band…. My inverted L is just five and half 
meters long, with about three meters moving up into the mast and the 
rest placed in a horizontal position . The wire that acts as a 
counterpoise is six meters long, and by using a homebrew multi-tap 
loading coil, I have used this antenna to transmit on 40 meters for 
local contacts too!!!
Amigos Des and Gabe, as you have just heard, there are many possible 
options to install HF antennas when you are very short of space, and I 
must add that it is a lot of fun to install different antennas and 
compare results, before settling down, as I did with my modest, yet 
efficient inverted L….that has allowed me to make many nice DX contacts 
on the 20, 17, 15 and 10 meter bands, despite the very low solar 
activity at this moment.
…….
Visit my workshop, join me for a tour of my workbench, where an old 
Pentium II motherboard was installed to a well preserved AT machine 
case, and provided with the LINUX operating system. The computer is now 
under test using software written for LINUX that allows working the now 
very popular PSK31 keyboard to keyboard communications mode. So far the 
rather slow by today standards 333 megaHertz CPU , an INTEL Mendocino , 
is letting me pick up many PSK31 stations on the 20 meters band , 
centering my scan on 14.070 kilohertz… I have now to install the 
permanent interface between both, one of my HF transceivers, a VHF two 
meters band rig and  the just revived Pentium II machine, in order to 
start working PSK31 on 20 meters on a regular basis, something that I 
want to be doing in the very near future. So those of you that are 
amateur radio operators and have already tested your stations using 
PSK31, be on the lookout for a two way QSO with a guaranteed QSL with 
CO2KK amigos!!!

And now as always at the end of the program, when I am here in Havana, 
this is Arnie Coro’s Dxers Unlimited HF plus low band VHF propagation 
update and forecast. Solar activity again at extremely low levels … 
solar flux at rock bottom 70 flux units …actually the forecast for
solar flux values through the end of the month of 70, 70, 65, 65, 65, 70 
and 70 for May 25-31. When the sun spotless for extended periods, we 
often sees solar flux values below 70, so a prediction of a solar flux 
of 65 implies no sunspots.

The three lowest solar flux values I am aware of were between July 
19-22, 1996, at the bottom of solar cycle 22, when they were 64.9, 66.1, 
65.4 and 65.1. There you
have it, the lowest, second lowest and third lowest solar flux
values, all during those four days of 1996.
This extremely low solar activity has sent the daytime maximum useable 
frequency curve into a nose dive, with only brief periods of good 
propagation at frequencies above 20 megaHertz. High probabilities of 
Sporadic E openings are still very much present, with an increase to 
happen by the end of the month as we enter into June, the month of the 
year that shows the highest number of Sporadic E events.
Hope to have you all listening to our mid week edition next Tuesday and 
Wednesday amigos, and don’t forget to send your signal reports and 
comments to arnie@xxxxxx or VIA AIR MAIL send a post card or letter to 
Arnie Coro, Radio Havana Cuba, Havana, Cuba

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