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Re: [HCDX] Dxers Unlimited's weekend edition for 4 -5 August 2007
Radio Havana Cuba
Dxers Unlimited
Dxers Unlimited's week end edition for 4-5 August 2007
By Arnie Coro
radio amateur CO2KK
Hi amigos radioaficionados worldwide... this is the weekend edition of
your favorite radio hobby program coming to you from sunny Havana, where
local temperatures have gone up to more than 35 degrees Celsius, and
frequent summer thunderstorms have limited my radio monitoring time,
because amigos, when the storm clouds approach, your only option is to
disconnect all radio equipment from the antennas, the power line and it
is also advisable to disconnect the earth grounding system too.
ITEM TWO: Extremely low solar activity continues.... the July official
sunspot average published by the Royal Observatory of Belgium was 10, a
clear evidence that we are still going trough the solar cycle's
minimum...And the most recent forecasts are telling us that during the
next several days a blank solar disk is to be expected, with zero
sunspots prevailing together with rock bottom figures of the 10.7
centimeters microwave solar flux. The extremely low solar activity is
causing very poor daytime propagation on the frequencies above 15
megaHertz...
More about solar activity and the HF plus low band VHF propagation
update and forecast as always at the end of the program...
ITEM THREE: Coming up in a few seconds, after a short break for station
ID... I am Arnie Coro, radio amateur CO2KK your host here in Havana...
...............
Yes, you are listening to the weekend edition of Radio Havana Cuba's
Dxers Unlimited, and here is ITEM THREE...
Our technical topics section of the show, that is devoted today to
answering a question from a listener. He is experimenting with the
Closed Coupled Resonators type of multiband antennas and wanted to know
more about this system that uses a single feedline connected to one of
the three close to each other antennas... Up to five antennas can be fed
using this system, but the more common CCRs or closed coupled resonators
antennas are two band or three band systems. As a matter of fact there
is a very well designed commercial amateur three band Yagi antenna array
that very succesfully uses the CCR system for the antenna's active
elements. Here is now my answer to the request by the Dxers Unlimited's
listener request:
Dear amigo: Nice to hear from you again, and learn about your antenna
experiments.
Here is all that I can tell you about my experience with the CCR
Close Coupled Radiators antenna system
The CCR wire antennas for the HF bands that I have tested here seem to
work very well after spending time adjusting them.
The maximum number of wire antennas that I think is possible is 3 or
perhaps 4.
You can start with a half wave dipole , fed via a 1 to 1 balun and using
a 50 ohms qood quality, well shielded coaxial cable.
Tune this antenna , for example, to resonance at 10.1 megaHertz ( the 30
meters band ).
Then you can add a wire cut as a half wavelength antenna for the 14.1
megaHertz frequency, placing it about 10 centimeters ( 4 inches away )
from the "fed dipole "
Your third antenna of the CCR system may be a half wavelength antenna
for the 18.1 mHz band, placing it also at the same distance of the "fed
dipole " ( This third one could also be for 21.1 , 24.9 or 28.4 mHz, as
required )
Then you must work with your SWR meter to obtain the best possible SWR
on the three antennas, something that is achieved by NOT MODIFYING the
length of the "fed dipole", but doing so with starting with the 20
meters band ( 14.1 mHz antenna ) and then optimizing the SWR for the
18.1 mHz antenna.
You may notice some interaction between the adjustments, but with the 10
cm ( 4 inches ) separation, this won't be really significant and you
will end up with a nice three band system that works very well You may
attempt to add a 4th wire , cut as a half wavelength element for the 15,
12 or 10 meter bands, and with very careful adjustments the 4 bands CCR
antenna will also work quite well, but the three band system is easier
to adjust.
You may install two antennas, one for the 40,30,and 20 meters band and
another one for 20,15 and 10 meters band.
Vertically polarized CCR antennas are trickier to adjust because
of the instability caused by the ground-counterpoise system that you may
have in use... In general CCR verticals must be installed with no less
than 8 radials cut for each of the bands that you are going to use, or
at least 8 radials for the lowest frequency band.. The radials must be
1/4 wavelength long, and you can intertwine another set of 8 radials 1/8
wavelength long at the lowest operating frequency.
I hope this helps you, and as a good friend said when he saw the CCR
wire 3 bander , the question is why don't simply tie the three dipoles
together at the center and feed the three at the same time via a one to
one balun...
ANSWER: Because the CCR is a new concept, and as I told him, one always
wants to learn about new antennas. Besides that, it seems like the CCR
three bander produces a cleaner vertical pattern than three pararell fed
dipoles ... And the next day, I received a very nice answer telling me
that his three band antenna was working very well on the 40, 30 and 20
meters band. He used fiberglass insulators to keep the three wires
separated from each other by about 10 centimeters or 4 inches, the
distance that was found to provide the best coupling and lowest standing
wave ratio.
.................
You are listening to the weekend edition of Dxers Unlimited, coming to
you when the daily solar flux is at the rock bottom levels of between 68
and 72 units... Now here is item four : Amateur radio satellites are in
orbit, not one or two, but several of them, but they all seem to be
getting very little use ... Today I will try here to attempt to
understand why the existing amateur radio satellites are seeing such
little use, and the first thing that comes to my attention is that among
radio amateurs there is very little knowledge about ham satellites and
how you can operate using them. After the fiasco caused by the failure
of the Oscar 40 super amateur satellite that was supposed to last for
many years in its elliptical orbit, interest in amateur satellites
dropped dramatically,and in my opinion it has never recovered. Another
contributing factor to the present low use of ham satellites was also
the failure of the popular Russian RS10 and RS12 easy sats, that could
be accessed using very simple antennas and equipment.
Now there are some signs of a revival in interest in the use of amateur
satellites, that focuses mainly on using them during ham radio contests
to boost the number of points by both club and individual stations, at a
moment when as we all know well, HF propagation conditions are very poor.
But, again, after carefully attempting to find out why ham radio
satellites see such little use nowadays, there seems to be yet another
important element, and that is the fact that the presently available
satellites are at very low altitude Earth orbits, so the time available
to make two way contacts is really very limited for even the best
possible conditions between two stations...
Prospects for a satellite with similar operating characteristics as the
doomed Oscar 40 are not optimistic at all, so my point of view is that
amateur radio satellite communications will remain at the present low
ebb for years to come... Yes, it is one of the more than 81 ways you and
I can enjoy the radio hobby, and at the present time it doesn't require
a lot of expensive equipment or sophisticated antennas...So, if you are
already an amateur radio station operator, explore the possibilities of
testing your ham station's satellite communications possibilities...At
these times of extremely poor HF propagation conditions , satellites
keep operating as usual, because they don't depend on solar activity to
provide two way communications...
.......
This is Radio Havana Cuba, the name of the show is Dxers Unlimited and
here is our next item... the ever popular, la numero uno YOU HAVE
QUESTIONS AND ARNIE HAS THE ANSWERS... Today's question was sent by
listener Doris from Atlanta, Georgia. She ASKS ARNIE , why is it
possible for her to sometimes pick up distant FM stations from her tenth
floor apartment location, that she can't hear on her car radio... Well
amiga Doris, the difference has to do with what engineers know as
effective antenna height, an ever important parameter for VHF, UHF and
Microwave operations... Your tenth floor apartment's effective height
above average ground extends the coverage of your FM radio a lot as
compared to the range that you can achieve with the car's FM radio
antenna that is at no more than about 2 meters or six feet above the
ground...
By the way amiga Doris, I am sending to you via e-mail the complete
detailed building instructions for a nice FM broadcast band antenna that
can be built using wire and PVC tubing. It is a two element cubical quad
that I have used here successfully to pick up FM broadcast band DX from
distances of up to two thousand miles when sporadic E openings have
happened...
And now amigos, as always at the end of the program , here is Arnie
Coro's Dxers Unlimited's HF plus low band VHF propagation update and
forecast... Solar activity is , and will continue to be for the next
several days at extremely low levels... with solar flux between 67 and
72 units and daily sunspot count at zero or very near zero... Expect
possible sporadic E openings by the end of the week, according to the
most recent forecasts... Expect daytime maximum useable frequencies not
higher than 18 megaHertz, and the best propagation conditions to be
available always after your local sunset. Join me next Tuesday and
Wednesday for the mid week edition of Dxers Unlimited amigos, and don't
forget to send me your signal reports and comments about the program to
arnie@xxxxxx <mailto:arnie@xxxxxx> , or VIA AIR MAIL to Arnie Coro,
Radio Havana Cuba, Havana, Cuba
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