Dxers Unlimited
Dxers Unlimited's mid weeek edition for 27-28 May 2003

By Arnie Coro

radio amateur CO2KK




Hi amigos radioaficionados around the world... Yes , we are now more than two million people
worldwide holding valid amateur radio operators licenses,and the number of us is expected to grow,
especially in third world nations. Amateur radio is one of the more than 70 ways that you and I can
have a very good time enjoying the radio hobby amigos ... Item one: Sporadic E skip season now in
really full swing .. Monday May 26th saw many single, double and even triple hope E skip openings to
the enjoyment of TV and FM Band Dxers . 6 meter band radio amateur operators also had a
fantastically busy day all along North America, the Caribbean, Mexico and Central America, as the
band stayed open for almos 18 hours ! Even late in the evening my local time here in Havana, I was
picking up several 6 meter band automatic beacon stations, that indicated that the band was open ...
With the many new amateur HF transceivers now coming with the 6 meter band included , it is very
interesting to see that many hams in North America and Europe are now exploring 6 meters for the
first time... Sporadic E skip ,the most misterious of all known ionospheric propagation modes is
capable of producing 60 dB over S 9 signals at distances of a thousand miles or more while running
powers as low as 10 Watts... More about Sporadic E later in this mid week edition of your favorite
listener oriented radio hobby program... Dxers Unlimited coming to you from Radio Havana Cuba...
Item two: Antenna topics section today will be devoted to a very interesting multi-band system that
may be installed even when space is at a premium. It makes use of a technique that is now becoming
the de-facto standard for new AM broadcast station's transmitting towers... Item three: Thunderstorm
season also in full swing, so be pretty sure that you have both your antennas and your radios
disconnected when you finish operating... a lightining strike even a couple of city blocks away from
your location may destroy your receiver... so follow your friend Arnie Coro's advice and be really
sure that once you finish listening or transmitting if you are an amateur radio operator, yes, be
really sure that both the antennas and the power plugs are disconnected... Item four: A new ham
radio little fun rig , the SSW, my most recent brainchild... SSW stands for the SIX SOCKETS
WONDER..., I'll be telling you more about this easy to build weekend project later in today's
program.

Now stay tuned right on this same frequency or keep you connection to our streaming audio from
www.radiohc.cu Margarita Delgado is my sound engineer and producer ... I am Arnie Coro in Havana..

.....

This is Radio Havana Cuba, the name of the show you are listening to is Dxers Unlimited, and here is
item two, our main feature for today...

Multi-band or totally broadband antennas are your only choice if you happen to have space for just
one antenna system. The multi-band approach is followed by many radio amateurs, because when
properly tuned, a multi-band antenna can be a really good performer . Today I will tell you about a
rather unique multiband antenna , that uses a technique that has become the de-facto standard for AM
broadcast stations antennas, both for new installations, and for retro-fitting to already existing
systems... The multi-band sloping loaded vertical monopole...

the SLVM antenna, is very easy to build , and materials for making yours can be found at any
hardware store. The SLVM or Sloping Loaded Vertical Monopole prototype's main radiating element is
just 6.70 meters long, that's about 22 feet.

The main element is made using 450 ohm window ladder line if it is available, and if not , you can
make a homebrew open wire line with the insulated spreaders keeping the wires about 100 millimeters
or 4 inches from each other... By the way and this is very interesting, the homebrew open wire line
provides more operating bandwidth than the factory made window line, but of course, it will take
more time to make your SLVM if you have to homebrew the main element.

The SLVM main element has , as you may realize, two parallel wires, and they are connected together
at one end.. You should actually solder them together at the top end of the antenna. At the low end
of the antenna, one wire goes to the live side of an assymetric antenna tuner, and the other wire
goes to ground and to the set of radials required by this antenna.

Now let't take a look at the shorted end of the antenna... there you have to install a loading
coil... Don't worry , I will give you details of the coil in just a moment... Then after the coil,
the SLVM uses a capacitive loading hat made from eight wires and a spreader to keep them separated
from each other at one end...

The SLVM uses both inductive and capacitive loading amigos !!! And it does require the use of at
least one quarter wave radial for each band , but four for each band will be much better. Now , let
me give you the details for the loading coil...

it is wound using number 18 enamelled wire,that is a wire with a diameter of dot 71 millimeters, the
coil is closewound, and the coil form is just a length of PVC pipe of 25 millimeters or one inch
diameter.You must wind 40 turns , tightly wound and then the coil must be weatherproofed, something
that is done by using PVC electricians tape first and applying several coats of high quality acrylic
paint...

Just for your information, two coils built using that weatherproofing technology and exposed to our
Cuban tropical rainy weather and intense UV radiation, lasted for more than seven years without any
signs of problems. As a matter of fact, I opened them up, just to see how they had done, and was
very happy to see that the two windings of PVC electricians tape and three coats of acrylic paint
had protected the coils so well that after seven years they were in what could be described as "like
new conditions" .

The SLVM is very easy to install, and mine is sloping from one of the towers into the backyard...
The loading wires are made from number 14 or no 12 copper wire, and it's best to remove the plastic
insulation and use the bare copper wires.. You will need eight wires ... but they all won't be of
the same length... Sounds funny, but the fact is that you want the wires to spread from a common
point, where they are soldered to the top end of the loading coil...so they can not be of the same
length... Here is how I do it... I place the antenna flat on the drive way, and then solder the coil
to the top end of the ladder line... Then I use a high impact polyethilene square of about 100 by
100 millimeters, that's 4 by 4 inches... to which I attach the other end of the loading coil... Well
actually, the coil is held in place to the polythilene square by two plastic cable ties... Then at
the other end of the plastic square, I drill eight holes, one for each of the capacity hat wires...
The are all soldered together and then via a flexible section of coaxial cable braid, they are
connected to the loading coil...

Now, I spread the wires uniformly , at the other end, where they are tied to the spreader... Your
best choice is to make the spreader from a section of UV resistant CPVC water pipe, and then run a
wire horizontally along the spreader to which you must solder each of the eight wires forming the
capacity hat... By the way , it this sounds a bit complicated, just visit www.radiohc.cu and read
the script of the show... I use a CPVC pipe spreader that is one meter long, just 3.28 feet in
length... The antenna is installed at a sloping angle between 20 and 45 degrees.

And the antenna tuner is , in my installation, just about one meter above the backyard's soil...
held in place by a wooden post. From the antenna tuner to the station I run a length of RG213 50 ohm
coaxial cable. The antenna tunes on the following bands.. 40, 30, 20, 17, 15, 12 and 10 meters...
and the only inconvenience is that the tuning up of the system is not automated, so I have to go out
to the backyard and set the antenna tuner's controls for the center of the band I want to
use.Normally I leave my SLVM tuned to the 30 meter band, one of my favorite spots to enjoy amateur
radio CW Morse code radiotelegraphy two way contacts.... If you want to learn more about the SLVM
Seven amateur Band low cost antenna, just drop me an e-mail to arnie@rhc.cu, again, very easy to
remember, but write it down now... send mail to arnie@rhc.cu , or VIA AIR MAIL, send a postcard to
Arnie Coro , Radio Havana Cuba, Havana, Cuba, and please specify that you want the information about
the low cost easy to homebrew SLVM 7 band antenna system

.....

Si amigos, yes my friends, out mes amis... radio is a hobby you and I enjoy in many different
ways... and the different seasons bring in different flavors of radio.. Now, during the early and
mid summer, we have sporadic E skip, a propagation mode that adds many new stations to TV Dxers
logbooks, and that FM broadcast band Dxers also enjoy a lot. 6 meter band amateur radio operators
are able to work stations as far as three thousand miles away at times, when more than one patch of
sporadic E ionization is available and double, or even triple hop signals reach your radio... Be on
the lookout for sporadic E signals, the 27 megaHertz citizen band is a very good indicator of
possible openings, when loud skip signals reach your CB radio !!!

Item four...The SSW, my latest fun vacuum tube project... actually it was something that came almost
of nowhere... when I was organizing some electronic components ... Suddenly I ended up with three
different types of quartz crystal sockets, and three different types of sockets for vacuum tubes...
I decided to put the six of them atop a piece of breadboard, and wire it up as crystal controlled
oscillator... The SIX SOCKETS WONDER was born !!! It can be used as a quartz crystal tester,
frequency marker with a crystal of the approppriate frequency, it can also be used as a secondary
frequency standard , by placing in one of the sockets a 10 megaHertz crystal that is then trimmed to
the exact frequency. The SSW can also be used as a test injection oscillator !!! AND OF COURSE, it
works as a pretty cute one tube transmitter. By placing a 6L6-G on the octal socket, and feeding
just 200 volts to the plate , the SSW produces a nice QRP or low power output of 2 Watts,with an
input power of 6 Watts, and that is about 30 percent overall efficiency, exactly what to expect, by
the book, from a power oscillator connected directly to the antenna... Three resistors, three fixed
and one variable capacitor and a homebrew coil wound on a small length of PVC pipe completes this
little weekend project that I am now using quite frequently on the 30 meter ham band ... QRP of
course !!!

And now amigos as always at the end of the show here is Arnie Coro's Dxers Unlimited's HF plus 6
meters propagation update and forecast... The sunspot effective number SSN is now around 77, while
the K index was reaching one again a figure higher than 3 Tuesday morning local time in Havana, so
obviously some kind of propagation disturbance was in progress , so probably conditions at the time
you listen to the show are not going to be all that good amigos... Meanwhile, there is a high
probability of more sporadic E events happening during the next six to eight weeks, so keep a
constant watch for possible E skip signals on your TV... AND, don't forget to send your signal
reports, QSL requests and radio hobby related questions to arnie@rhc.cu, or VIA AIR MAIL to Arnie
Coro, Radio Havana Cuba, Havana, Cuba... see you all at the weekend edition of Dxers Unlimited, next
Saturday and Sunday UTC days !!!