Radio Havana Cuba

Dxers Unlimited

Dxers Unlimited's mid week edition for 4-5 July 2006

By Arnie Coro

radio amateur CO2KK

Hi amigos radioaficionados... welcome to the mid week edition of your
favorite radio show, now heard in New Zealand on an almost daily basis
due to the very interesting propagation path on the 31 meters band
around 0500 hours UTC that we are seeing on the 9550 kiloHertz frequency.

According to reports I have received here, our 9550 kiloHertz , 31
meters band English language broadcast on the air from 05 to 07 UTC
using one of the new HQ type ominidirectional antennas is been received
in New Zealand with pretty good quality... A very interesting
propagation path indeed... I remember working an amateur radio contest
during the past solar minimum, when our club station got a lot of points
and multipliers by working on the 40 meters band around that time, using
a simple 2 element wire Yagi beaming into the Pacific ...As solar cycle
23 continues to go down, we may see more and more of this type of nearly
antipodal propagation....

Item two: Thank you amigos, for the many nice birthday congratulations
received here... it was very rewarding to hear from so many long time
listeners and friends !!!

Be assured that all your congratulations messages had

a great effect on me, and that I will try to keep Dxers Unlimited as
your favorite radio hobby program, by doing all possible efforts so that
the program will be as interesting as ever on every future edition...

Item three: Milliwatting, that 's the name of running amateur radio
equipment below the 1 Watt power level... remember that 1 Watt is
equivalent to one thousand milliwatts!!! And yes, running here 120
milliWatts to a small receiving type NPN silicon transistor, I was able
to work

recently an amateur station in Western Canada, while using a very simple
wire antenna... The power for the 120 milliWatts rig came from a 12
volts gelcell, of the type used

for powering computer UPS systems... A 10 dB booster amplifier is now
under construction, so that , when properly calibrated, the new QRP
MilliWatter will provide the option of two power output levels at the
flip of a switch.... 100 milliWatts and 1000 MilliWatts... The little
rig is crystal controlled, with a VXO type of oscillator that can be shifted

around the 14.032 kiloHertz frequency of the quartz crystal... Maybe one
of these days, if you are already and amateur radio station operator, we
can have a nice CW morse code contact with my little new QRP MilliWater,
that by the way and for your information, was built using only recycled
components....

Stay tuned for more radio hobby related items coming to you from Havana.
I am Arnie Coro your host here at Dxers Unlimited...

......

Si amigos, this is Radio Havana Cuba, the name of the show is Dxers
Unlimited, and we are now testing another antenna... From 05 to 07 UTC
on 11760 kiloHertz our new Pacific Coast of North America antenna is in
use... again the frequency is 11760 kiloHertz, the program is in English
and the antenna is beaming 310 degrees azimuth from Havana, so I expect
it to be delivering a very nice signal from Northern Mexico, California,
Oregon , Washington and Northwest Canada... send your signal reports if
you are located in the coverage area, and a nice special QSL card will
be autographed for you and sent VIA AIR MAIL...

Item five: Lots of ham radio freeware programs, very well written, and
they run very well even when using older computers... the source of them
... LINUX freeware for amateur radio... I now have installed a very nice
digital modes communications program, that runs really well on an old
Pentium I machine with just 32 megs of memory... And those LINUX
programs are really compact, they are very well written and use up very
little disk space. I am now looking to try to find HF propagation
forecasting software written for LINUX machines, but so far my search
has proven to be fruitless... So amigos, if any of you Dxers Unlimited's
listeners around the world knows about any HF propagation forecasting
software for the Linux operating systems, please send me an e-mail with
the URL from where to download it to arnie@rhc.cu, again arnie@rhc.cu,
and don't forget to include also a signal report and comments about the
program...

........

This is Dxers Unlimited's mid week edition , coming to you from Havana,
I am Arnie Coro radio amateur CO2KK , and here is item six of today's
show: The "other" fan antenna is a lot of fun to homebrew... Why the
name... the "other" fan antenna... well it's because it is not the
classic multiple wires HF or VHF fan type antenna... This one is a
vertical that is built using the protective metal spokes cover of an
discarded electric fan... The typical 12 to 16 inch desk fan, that is
from 30 centimeters to about 37.5 centimeters diameter fan protective
cover is an almost ideal ground plane for a third of a wavelength
vertical antenna for the two meters band, and it can also be used as the
groundplane for a 70 centimeters band vertical array of phased linear
elements. My first "other fan" antenna is always ready to be transported
to wherever fast deployment of an emergency 2 meters band station may be
required. In my particular antenna design, I use a small length of
coaxial cable as a series reactance tuning capacitor for the one third
of a wavelength , or 120 electrical degrees high vertical antenna, that
in this case is just 67 centimeters high, and made of a 10 millimeters
aluminum tubing. The center of the 50 ohms coaxial feedline is connected
to the outside shield or braid of a short length of 50 ohms coaxial
cable, and the center is then connected to the vertical element. The
antenna is trimmed for minimum standing wave ratio by cutting small
lengths of the "coaxial cable capacitor", until a one to one SWR is
achieved... You will need a VHF standing wave ratio meter to tune up the
antenna... I have built my "fan protective cover ground plane vertical "
in such away that it can be easily transported, something that is
achieved by installing a SO239 female coaxial connector at the exact
center of the fan protective cover, assuring that very good electrical
contact exists between the connector and the metal hub of the fan
protective cover. The vertical antenna element is fixed to a 4 mm male
banana plug, so that you only need to plug in the vertical radiator
element in order to have the antenna ready for action !

Yes, you heard it right... an old 12 or better yet 15 or 16 inch
diameter fan metal protective cover is an almost ideal ground plane for
your new homebrew ultra low cost "FAN" antenna that can be used on both
the 2 meters and the 70 centimeters amateur band... and in those
countries where the 1.25 meters or 220 megHertz band is authorized for
ham radio use, the old fan protective cover will also be ideal to make a
"FAN" ground plane, or as a local friend calls it

a FANPLANE antenna... By using a air spaced small variable capacitor,
located at the underside of the fan protective,

you can tune the vertical one third of a wavelength element to minimum
standing wave ratio in a few minutes !!!

You see amigos, ham radio ingenuity is always finding new ways to enjoy
our hobby , and while spending very little money... The actual cost of
the "FAN PLANE" antenna is just the cost of the SO239 female coaxial
connector that is used a the center of the fan metal protective cover...
and even that can be replaced with a home brew insulator made from a
length of RG 17 cable center polyethilene insulator !!!

......

Well after our FAN PLANE antenna description, let's move on to a request
made by several members of the very popular GLOWBUGS e-mail list, that
is devoted to the use of vacuum tubes for amateur radio equipment...
They all want to know more about my latest "A LA COLLINS" regenerative
radio receiver design... Just to give you an idea of that project that
has taken almost all my spare time for the past two months or so, mainly
during the weekends, all I can say that the time spent on it has been
worth every single minute.

I was finally able to sit down and design the near optimum bandpass
input filter for the frequency ranges from 500 kiloHertz to 2.0
megaHertz, from 2.0 megahertz to 6.0 megaHertz and from 6.0 to 12.0
megaHertz... and have still to crunch numbers for designing the 12.0 to
22 megaHertz filter... All of these bandpass filters use homebrew high Q
optimized coils, that are built using the optimum diameter and length
required to obtain the maximum Q or figure of merit. I have yet to find
enough ceramic coil forms to build all the filters, so in the mean time,
I have used polyethylene coil forms that came from the center conductor
of the large diameter RG17 or RG19 type coaxial cables. A second less
desired option was to wind the coils using lengths of white PVC pipe,
and I have yet to measure the difference in Q factor between the coils
wound on the high quality low loss ceramic coil forms and identical ones
wound using white PVC pipe forms. As soon as results of these tests are
available I will publish them on the GLOWBUGS list...

The air spaced variable capacitors used for the bandpass filters that I
have already finished building are standard

dual gang approximately 350 to 400 picofarads receiving type variable
capacitors, of which I use just one section for tuning each of the
filter tuned circuits. In other words , each section is individually
tuned for optimum efficiency, and no attempt was made to make the tuning
of the two filter sections to keep tracking ... The filters are housed
inside steel boxes, with a lot of space between the coils and the walls
of the boxes, because I didn't want to spoil the Q of the coils... So,
no amigos, this is not a miniature receiver at all...

And all I can say so far, is that the individual fully shielded

band pass filters, when tested between the antenna and the input of even
very nice commercial HF receivers, provide a significant improvement in
performance , due to the added selectivity at the front end of the
radio... In an upcoming edition of Dxers Unlimited I will continue the
step by step description of Arnie Coro's " A LA COLLINS" Regenerodyne
Receiver... and now as always at the end of the show , here is Dxers
Unlimited's HF plus low band VHF propagation update and forecast...
solar activity has increased during the past several days, but now is
expected to remain at low to very low levels, and solar flux has reached
the 90 mark after a long period of very low figures , ranging between 70
and 80 units... Sunspot number is at 38 , and that's the optical sunspot
count, a high speed solar wind gust coming from a coronal hole is
expected to hit the Earth's magnetosphere and if this happens high
latitude propagation conditions will worsen, and AM broadcast stations
from the South will provide very good signals during today's and
tomorrow's evenings... Don't forget to send your QSL requests, signal
reports and comments to arnie@rhc.cu or VIA AIR MAIL send a post card or
letter to Arnie Coro, Radio Havana Cuba,Havana, Cuba