"Helmut Wabnig" hwabnig@ .- --- -. dotat wrote in message
...
On Wed, 04 Feb 2009 16:56:30 -0800, Richard Clark
wrote:

On Wed, 4 Feb 2009 22:15:09 +0000, KE5LDO
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


no no,
that is the perfect example of a dummy load with a radiating cable.

w.
-
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

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?


"Wayne" wrote in message
...

"Helmut Wabnig" hwabnig@ .- --- -. dotat wrote in message
...
On Wed, 04 Feb 2009 16:56:30 -0800, Richard Clark
wrote:

On Wed, 4 Feb 2009 22:15:09 +0000, KE5LDO
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


no no,
that is the perfect example of a dummy load with a radiating cable.

w.
-
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" wrote in message
...
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?


Sure. However, I'm not recommending it for anything. As I recall it was a
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.

Wayne wrote:
"Spin" wrote in message
...
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?


Sure. However, I'm not recommending it for anything. As I recall it was a
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.



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.

Jim Lux wrote:
Wayne wrote:
"Spin" wrote in message
...
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?


Sure. However, I'm not recommending it for anything. As I recall it
was a 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.


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.


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

"Jim Lux" wrote in message
...
Wayne wrote:
"Spin" wrote in message
...
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?


Sure. However, I'm not recommending it for anything. As I recall it was
a 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.

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.


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" wrote in message
...

"Jim Lux" wrote in message
...
Wayne wrote:
"Spin" wrote in message
...
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?


Sure. However, I'm not recommending it for anything. As I recall it
was a 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.

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.


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

.... and replacing it with a short circuit! (important point, omitted from
posting)

Spin wrote:
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

On Thu, 05 Feb 2009 12:29:16 -0800, Roy Lewallen
wrote:

Spin wrote:
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

Methinks you forgot inexpensive. Still pick any two.

On Thu, 5 Feb 2009 08:05:40 -0800, "Wayne"
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.

73's
Richard Clark, KB7QHC