"Arnie Coro Antenna"
KE5LDO
I built this years ago as a quick antenna for receiving and
transmitting. It is name after Havana Cuba's Arnie Coro, since He came
up with it over 20 years ago.
1. Take a 45 ft/15 meter 52 ohm Coax, or multiples up or down.
2. Dress it as center conductor and braid on both ends.
3. Solder a 50 OHM resisitor on one end, connecting the center and the
braid.
4. On the other end, solder a piece of coax. with braid to center
conductor, center conductor to braid. On the other end, solder a
PL-259, or whatever your rig accepts.. Then connect it to your
receiver/transmitter.
5. You now have a balanced, low noise antenna. I would suggest a 10
watt or hgher resistor for the amount of power you are going to use if
transmitting.
--
KE5LDO
nm...@wt.net
It's not April 1, 2009 yet... :/
Richard Clark
<KE5LDO....@radiobanter.com> wrote:
>
>I built this years ago as a quick antenna for receiving and
>transmitting. It is name after Havana Cuba's Arnie Coro, since He came
>up with it over 20 years ago.
Did Fidel put Arnie against the wall when he published how to
construct a TRANSMITTING antenna?
He should have if for no other reason than the arbitrary instructions:
>1. Take a 45 ft/15 meter 52 ohm Coax, or multiples up or down.
What significance is 45 feet (or 15 meters)? Is this a magic number?
>2. Dress it as center conductor and braid on both ends.
Dress right, or dress left?
>3. Solder a 50 OHM resisitor on one end, connecting the center and the
>braid.
Wouldn't a 50 Ohm resistor present a SWR of 1.04:1? This isn't about
efficiency, is it?
>4. On the other end, solder a piece of coax. with braid to center
>conductor, center conductor to braid. On the other end, solder a
>PL-259, or whatever your rig accepts.. Then connect it to your
>receiver/transmitter.
Shouldn't this be 4(a) and 4(b)?
For 4(a) What happened to the resistor?
For 4(b) Why the connector? Just run the existing line out to 4(a)
>5. You now have a balanced, low noise antenna. I would suggest a 10
>watt or hgher resistor for the amount of power you are going to use if
>transmitting.
Why would you use a resistor for receiving? If it were for
transmitting, I can see why Cuba is still under domination by the
Castros.
Something must have been lost in translation - or maybe the process of
getting through the communist censors. Perhaps this was the CIA
antenna design for the Bay of Pigs.
73's
Richard Clark, KB7QHC
Tom Donaly
You can look up Arnie's website on Google, go there, and read for
yourself what Arnie's idea of an antenna is. The poster is pulling a
fast one.
73,
Tom Donaly, KA6RUH
Sal M. Onella
"Tom Donaly" <dtdo...@sbcglobal.net> wrote in message
news:PHtil.11844$W06....@flpi148.ffdc.sbc.com...
> You can look up Arnie's website on Google, go there, and read for
> yourself what Arnie's idea of an antenna is. The poster is pulling a
> fast one.
Arnie Coro's website does discuss the item described.
http://www.mail-archive.com/hard-c...@hard-core-dx.com/msg18595.html
He doesn't claim it works well (nor should he).
At one point he describes burying it to stealth it. When I was moving an
antenna, I had both dipole elements laying on the ground but still
connected. Just for laughs, I tuned it up. I could hear a few other people
but nobody could hear me. I think burying an HF antenna should be followed
by a shopping trip for some writing paper and stamps. You'll need 'em.
Helmut Wabnig
wrote:
no no,
that is the perfect example of a dummy load with a radiating cable.
w.
Wayne
"Helmut Wabnig" <hwabnig@ .- --- -. dotat> wrote in message
news:cv5lo4hk84jar17m2...@4ax.com...
At one time, I lived in an apartment and used a similar, shorter antenna for
2 meter operation via a repeater. It was easy to build, and worked fine
because I didn't need much signal to hit the repeater.
--Wayne
Spin
antenna you had? I wonder if one were to make a longer version would it
have gain & a wider bandwidth?
"Wayne" <mygarb...@verizon.net> wrote in message
news:gmf2ol$h9e$1...@news.motzarella.org...
Wayne
"Spin" <noe...@alone.invalid> wrote in message
news:MBEil.1193$N02...@nwrddc02.gnilink.net...
> Wayne........That's interesting.....Can you elaborate on that 2 meter
> antenna you had? I wonder if one were to make a longer version would it
> have gain & a wider bandwidth?
>
>
quarter wave of coax terminated in a 10 watt dummy load. The quarter wave
was connected as previously described, with the shield of the quarter wave
connected to the center conductor of the feedline and the shield of the
feedline connected to the center conductor of tthe quarter wave. I was just
trying to get a dummy load to radiate enough for a short path to a repeater.
(Transmitter ran 10 watts)
At a different time, I simply terminated a feedline (low quality RShack
RG-58) with a 10 watt carbon resistor (unshielded and 3 inch leads). It
worked about the same.
However, remember that I was only trying to hit a single repeater, and a
whip antenna with just a few milliwatts would have worked on that particular
path. The "antenna" was very poor, but there may be paths where it is an
acceptable compromise.
Jim Lux
Think of this as a variant on taking a 1/4 wave of wire and attaching it
to the center conductor of the feedline (or, just stripping 1/4wave of
shield off the coax) with no choke, balun, or anything else. It's a sort
of sleeve dipole: The "outside" of the feedline coax essentially acts as
the other half of the dipole.
Depending on where it's installed, it might work, might not. No
decoupling means that the whole feedline potentially radiates, etc.
Probably no worse than a lot of other improvised antennas.
Put a really good choke around the coax at the 1/4 wave point, and it
starts to look better, but, having the feedline essentially hanging off
the end of the dipole means that you've got conductors in the high E
field part of the antenna, so there will be capacitive coupling.
Doing the Coro style thing with the resistor, etc, in effect makes this
another of the many "resistively loaded dipole" schemes where you give
up some efficiency in exchange for a better match. No different in
concept (although different in design) from the T2FD sorts of things
from B&W, etc.
Tom Donaly
I notice Arnie has a terminated, folded dipole or whatever you call it
on his web page. He doesn't offer it as anything other than what it is.
Most of his stuff has always been for people of limited means who still
want to enjoy amateur radio. Cubans are good at that type of thing
because their crappy economic system and the American boycott have
forced them to be that way.
73,
Tom Donaly, KA6RUH
Richard Clark
wrote:
>At one time, I lived in an apartment and used a similar, shorter antenna for
>2 meter operation via a repeater. It was easy to build, and worked fine
>because I didn't need much signal to hit the repeater.
Hi Wayne,
In my basement shack, using a 300mW 2M Alinco HT, I can hit my buddy's
repeater 10 miles away. The HT's antenna, fully extended, is only an
8 inch whip.
It doesn't need a resistor. It doesn't need fancy cable preparation.
It is roughly one-hundredth the size of Arnie's, operating at
one-twentieth the wavelength as Arnie's(?).
So, the amended Arnie's minimalist design:
1. Take a 45 ft/15 meter 52 ohm Coax;
2. connect center conductor and braid together on both ends;
3. throw a 50 OHM resistor over your right shoulder for luck;
4. then connect that coax through a tuner to your transceiver;
5. listen and talk to the world.
This pretty much describes my antenna that I could use to listen to
Radio Habana Cuba (and more) when I was a kid. However, I was driven
by economic necessity to be more minimalist. For instance:
1. Take a 45 ft/15 meter surplus armored 1" multi conductor cable;
2. strip out the wire from inside the cable for other projects;
3. keep the 50 OHM resistor for other projects;
4. then connect that cable shell through a tuner to my receiver;
5. listen to the world.
Using the armored shell was an extravagence, as I could have had used
one of the wires that formerly ran through it. That antenna heard
Habana, Quito, Sydney, and Cape Town (or Jo'burg) quite easily.
My radios back then were a Knight Kit Star Roamer, a BC348, a BC453,
and a RBB-1. I used the BC348 as a highly selective, second IF
(85kHz) conversion to the other sets.
Harold E. Johnson
> and a RBB-1. I used the BC348 as a highly selective, second IF
> (85kHz) conversion to the other sets.
>
> 73's
> Richard Clark, KB7QHC
More likely, it was the BC-453 you used for the selectivity although it
wouldn't tune as high in frequency as the IF in the BC348. Must have used it
for the Knightkit
W4ZCB
Roy Lewallen
> Wayne........That's interesting.....Can you elaborate on that 2 meter
> antenna you had? I wonder if one were to make a longer version would it
> have gain & a wider bandwidth?
Just remember the general rule for antennas: small - efficient -
broadband: pick any two.
Roy Lewallen, W7EL
Roy Lewallen
>
> Arnie Coro's website does discuss the item described.
> http://www.mail-archive.com/hard-c...@hard-core-dx.com/msg18595.html
> He doesn't claim it works well (nor should he).
>
> At one point he describes burying it to stealth it. When I was moving an
> antenna, I had both dipole elements laying on the ground but still
> connected. Just for laughs, I tuned it up. I could hear a few other people
> but nobody could hear me. I think burying an HF antenna should be followed
> by a shopping trip for some writing paper and stamps. You'll need 'em.
>
Buried antennas were seriously investigated by the military some time
ago, and are probably still in use. While terribly inefficient, some can
radiate enough to be useful, and invisibility can be an asset. I was
told long ago that the reason NEC-4 was prohibited for export for so
long was that it could be used for designing buried and therefore
invisible antennas.
Roy Lewallen, W7EL
Michael Coslo
> Dress right, or dress left?
Took some balls to ask that question... ;^)
- 73 de Mike N3LI -
Richard Clark
Hi Harold,
You are right, I got the BCs backwards.
Jim Lux
Actually, I think it was the NEC 3 variant that first introduced buried
wires, and was classified as Defense Critical Technology. "The only
difference in the capabilities of these codes is that NEC-3 can model
wires that are buried or penetrate from air into the ground, while NEC-2
is limited to antennas in free space or above a ground plane."
from Burke's NEC validation paper published at that conference in Ankara
Turkey in 1989.
That paper also mentions an experimental version NEC3VLF (improving
performance for electrically small antennas), NEC4X (better modeling of
endcaps), NEC3I (for insulated wires), NEC-GS (ground screens), etc.,
all of which probably wound up in NEC4 in one way or another.
A notable export controlled application of such codes is modeling wires
submerged in seawater.
The export controls still exist, by the way, for NEC4.. when you get a
copy, don't you have to certify who the end user is? and agree to ITAR
compliance, etc.
https://ipo.llnl.gov/technology/software/documents/NEC.pdf
>
> Roy Lewallen, W7EL
>
christofire
"Jim Lux" <james...@jpl.nasa.gov> wrote in message
news:gmf7bc$ker$1...@news.jpl.nasa.gov...
The section of line at the end, terminated with the resistor, will present
something like 50 ohms between its terminals (outer and inner) at the point
where it is connected to the feedline, even if its terminals are reversed,
so if the outside surface of its outer conductor and the outside surface of
the outer conductor of the feedline present some sort of dipole to the same
point, the ~50 ohms will shunt the terminal impedance of that dipole. So if
the dipole actually radiates in the manner of a half-wave wire dipole its
VSWR could be improved by omitting the resistor.
Working: VSWR = (1+{Rho})/(1-{Rho}) where {Rho} is the magnitude of Rho, the
reflection coefficient for voltage at the dipole's drive point and Rho =
(ZL-Z0)/(ZL+Z0) where ZL is the impedance of the load at the end of the
feedline of characteristic impedance Z0.
~72 ohms from a half-wave dipole alone yields Rho = 0.16 for Z0 = 52 ohms,
and so VSWR = 1.38.
~72 in parallel with ~50 = ~29.5 ohms for the parallel combination yields
Rho = -0.28 so {Rho} = 0.28 and VSWR = 1.78.
Of course, if the 'dipole' does not radiate in the manner of a half-wave
wire dipole then this may not apply (e.g. if it is buried).
Chris
christofire
"christofire" <chris...@btinternet.com> wrote in message
news:YKudnWQm1avC9RbU...@bt.com...
... and replacing it with a short circuit! (important point, omitted from
posting)
Roy Lewallen
> . . .
> The export controls still exist, by the way, for NEC4.. when you get a
> copy, don't you have to certify who the end user is? and agree to ITAR
> compliance, etc.
>
> https://ipo.llnl.gov/technology/software/documents/NEC.pdf
Until a few years ago, NEC-4 could only purchased by a U.S. citizen for
use within the U.S. Anyone else would have to apply for an exception via
diplomatic channels.
Now, there are no restrictions except for a very few prohibited
countries (e.g., North Korea). Licenses are routinely granted for users
all over the world. The program is, however, still protected by copyright.
Roy Lewallen, W7EL
Sal M. Onella
"Roy Lewallen" <w7...@eznec.com> wrote in message
news:jI-dneBR7_230RbU...@posted.easystreetonline...
>
> Buried antennas were seriously investigated by the military some time
> ago, and are probably still in use. While terribly inefficient, some can
> radiate enough to be useful, and invisibility can be an asset.
Agree.
I didn't mean to imply that a buried antenna wouldn't work at all. Dirt's
not a perfect shield material, which is what would be required for zero
radiation.
Cecil Moore
> I didn't mean to imply that a buried antenna wouldn't work at all.
How about in a dry sandy desert?
--
73, Cecil http://www.w5dxp.com
JosephKK
wrote:
Methinks you forgot inexpensive. Still pick any two.
Sal M. Onella
"Cecil Moore" <nos...@w5dxp.com> wrote in message
news:nzVil.13060$as4....@nlpi069.nbdc.sbc.com...
I don't know.
John Smith
> I built this years ago as a quick antenna for receiving and
> transmitting. It is name after Havana Cuba's Arnie Coro, since He came
> up with it over 20 years ago.
Frankly, I have wondered about this. If I hooked an antenna up to my
dummy load, how far could I transmit? What kind of kilowatt signals
would be able to move my meter needle?
Or, was that only a dream? <grin>
Regards,
JS
John Smith
> ...
> In my basement shack, using a 300mW 2M Alinco HT, I can hit my buddy's
> repeater 10 miles away. The HT's antenna, fully extended, is only an
> 8 inch whip.
> ...
> 73's
> Richard Clark, KB7QHC
Don't be shy, or try to be modest ... it is guys like you that made
first contact with the aliens!
Modesty will get you no where ... <sly smile>
Regards,
JS
John Smith
WOW! I thought only males had those!
Thanks, you learn something new everyday ... ;-)
Regards,
JS