Joe Bloe wrote:
However, I did
get a two bits of good information, a closer explanation of the effect
of a fat conductor antenna, and a web-site with a calculator for just
such a thing.

You can probably arrive at the same correct technical
conclusions by downloading the free demo version of
EZNEC and selecting the diameter of the conductor.
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
Joe Bloe wrote:

However, I did
get a two bits of good information, a closer explanation of the effect
of a fat conductor antenna, and a web-site with a calculator for just
such a thing.


You can probably arrive at the same correct technical
conclusions by downloading the free demo version of
EZNEC and selecting the diameter of the conductor.

No doubt, Cecil. Of course this wasn't where the conversation started
at. I haven't tried EZNEC to model a cage antenna, will it do it? Or do
you just make the wires really thick? And how does really thick wire
compare to a cage of the same relative diameter?

- 73 de Mike KB3EIA -

On Thu, 17 Aug 2006 21:33:17 -0400, Mike Coslo
wrote:

how does really thick wire
compare to a cage of the same relative diameter?

Hi Mike,

Close, but no cigar. Actually, the degree of closeness depends on how
well the cage represents the solid. That degree is a function of the
number of wires that form the skeletal shape. Four is pretty lousy,
120 would be outstanding. Then there is something in the middle:

http://home.comcast.net/~kb7qhc/ante.../Cage/cage.htm
offers an example that may be suitable. This is a 4 meter tall
antenna that tunes all frequencies from 20M through 10M.

73's
Richard Clark, KB7QHC

http://home.comcast.net/~kb7qhc/ante.../Cage/cage.htm
offers an example that may be suitable. This is a 4 meter tall
antenna that tunes all frequencies from 20M through 10M.

73's
Richard Clark, KB7QHC

What is the diameter of the antenna design?

buck
n4pgw

--
73 for now
Buck
N4PGW

Richard Clark wrote:
On Thu, 17 Aug 2006 21:33:17 -0400, Mike Coslo
wrote:

how does really thick wire
compare to a cage of the same relative diameter?

Hi Mike,

Close, but no cigar. Actually, the degree of closeness depends on how
well the cage represents the solid. That degree is a function of the
number of wires that form the skeletal shape. Four is pretty lousy,
120 would be outstanding. Then there is something in the middle:

http://home.comcast.net/~kb7qhc/ante.../Cage/cage.htm
offers an example that may be suitable. This is a 4 meter tall
antenna that tunes all frequencies from 20M through 10M.

A single fat wire can be a reasonable approximation to a cage provided
that the diameter is very small compared to a wavelength. (The NEC
recommendation is around 0.02 wavelength maximum diameter, which you can
find in the EZNEC manual in the Building The Model/Modeling The Antenna
Structure/About Wires topic.) For a cage of only a few parallel wires,
you can use an equivalent diameter as follows, where d = the wire
diameter and s = ctr-ctr wire spacing, everything in the same units:

2 wires - Equiv. dia. = 1.414 * sqrt(d * s)
3 wires in a triangle - Equiv. dia. = 1.587 * cube root(d * s^2)
4 wires in a square - Equiv. dia. = 1.834 * fourth root(d * s^3)
N wires equally spaced on a circle with radius r -
Equiv. dia. = 2 * r * Nth root((N * d) / (2 * r))

-- derived from equations in Fundamentals of Coupled Lines and Multiwire
Antennas, by Hidenari Uchida (Sasaki, 1967).

I've made myself a note to include this in a future EZNEC manual update.

For cages larger than about 0.02 wavelength diameter, you should model
the individual wires.

Roy Lewallen, W7EL

Mike Coslo wrote:
Cecil Moore wrote:
You can probably arrive at the same correct technical
conclusions by downloading the free demo version of
EZNEC and selecting the diameter of the conductor.

No doubt, Cecil. Of course this wasn't where the conversation
started at. I haven't tried EZNEC to model a cage antenna, will it do
it? Or do you just make the wires really thick? And how does really
thick wire compare to a cage of the same relative diameter?

You can use the free demo version to model a large diameter
radiator with up to 20 segments. For the actual multi-wire
cage antenna, one would need to spring for the non-free
version which is, IMO, the best bargain in ham radio
antenna simulation software. Why ask questions here when
the answer is available to any individual who springs for
EZNEC?
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
Mike Coslo wrote:
Cecil Moore wrote:
You can probably arrive at the same correct technical
conclusions by downloading the free demo version of
EZNEC and selecting the diameter of the conductor.

No doubt, Cecil. Of course this wasn't where the conversation
started at. I haven't tried EZNEC to model a cage antenna, will it do
it? Or do you just make the wires really thick? And how does really
thick wire compare to a cage of the same relative diameter?

You can use the free demo version to model a large diameter
radiator with up to 20 segments. For the actual multi-wire
cage antenna, one would need to spring for the non-free
version which is, IMO, the best bargain in ham radio
antenna simulation software.

No doubt, it is great software.



Why ask questions here when
the answer is available to any individual who springs for
EZNEC?


First thing is that Mr Bloe didn't start the thread off as what the
bandwidth of a cage dipole was. The bandwidth question came later. So
while it is good advice to send someone to EZNEC, it is kind of
presuming the person already knows the answer to their question when you
expect them to *not ask the question* in the first place.

I find the topic interesting, and certainly the feedback I've gotten
from Richard and Roy have been very illuminating. So I encourage more on
the topic.

Sure beats those 2000 post threads we seem to get in here! I'd sooner
see topics such as this than you and W8JI sharpening your claws on each
other......hehe

- 73 de Mike KB3EIA -

Since it appears that the benefit of the cage is bandwidth I ran a few
scenario's with EZNEC and a 40 Meter vertical that is 33 feet tall.
note that I did not correct for resonance shifting and that I am
assuming that whatever the mesh is, it will not beat a solid.

http://www.dixienc.us/28FtVert/BandwithVsDia.htm

Given that most of us agree that trying to better a 2:1 SWR is into
diminishing returns I believe this illustrates the cage's loss of
popularity.

Defiantly an appealing sight though...

de W8CCW John


On Wed, 16 Aug 2006 14:06:06 -0700, Joe Bloe
wrote:

Hello,
My attention has been caught by the abilities of a "Fat Conductor"
for an antenna. I understand that this has been achieved by using
what is (little known about) a Caged Di-Pole. I have seen them before
in older photographs, mostly draped over an old steamship, stem to
stern.

The Caged Di-Pole is supposed to be very well suited for weak signal
reception. I know that a Yagi can do very well in this regard, but
its the art of it that I'm interested in, and as far as I can see,
it's almost an lost aspect of HAM radio nowadays.

Does anybody remember these things?

73's
Rob
John Ferrell W8CCW

"John Ferrell" wrote in message
...
Since it appears that the benefit of the cage is bandwidth I ran a few
scenario's with EZNEC and a 40 Meter vertical that is 33 feet tall.
note that I did not correct for resonance shifting and that I am
assuming that whatever the mesh is, it will not beat a solid.

http://www.dixienc.us/28FtVert/BandwithVsDia.htm

Given that most of us agree that trying to better a 2:1 SWR is into
diminishing returns I believe this illustrates the cage's loss of
popularity.

Defiantly an appealing sight though...

de W8CCW John


On Wed, 16 Aug 2006 14:06:06 -0700, Joe Bloe
wrote:

Hello,
My attention has been caught by the abilities of a "Fat Conductor"
for an antenna. I understand that this has been achieved by using
what is (little known about) a Caged Di-Pole. I have seen them before
in older photographs, mostly draped over an old steamship, stem to
stern.

The Caged Di-Pole is supposed to be very well suited for weak signal
reception. I know that a Yagi can do very well in this regard, but
its the art of it that I'm interested in, and as far as I can see,
it's almost an lost aspect of HAM radio nowadays.

Does anybody remember these things?

73's
Rob
John Ferrell W8CCW

What if all the wires are not the same length. I know my friends were able
to cover all of 75/80 without retuning but this may have been because of the
losses in the steel wire they were using..

FINALLY!!! Something good comes from being FAT. When does a FAT antenna become
OBESE??

:-)

Jimmie D wrote:

"John Ferrell" wrote in message
...

Since it appears that the benefit of the cage is bandwidth I ran a few
scenario's with EZNEC and a 40 Meter vertical that is 33 feet tall.
note that I did not correct for resonance shifting and that I am
assuming that whatever the mesh is, it will not beat a solid.

http://www.dixienc.us/28FtVert/BandwithVsDia.htm

Given that most of us agree that trying to better a 2:1 SWR is into
diminishing returns I believe this illustrates the cage's loss of
popularity.

Defiantly an appealing sight though...

de W8CCW John


On Wed, 16 Aug 2006 14:06:06 -0700, Joe Bloe
wrote:


Hello,
My attention has been caught by the abilities of a "Fat Conductor"
for an antenna. I understand that this has been achieved by using
what is (little known about) a Caged Di-Pole. I have seen them before
in older photographs, mostly draped over an old steamship, stem to
stern.

The Caged Di-Pole is supposed to be very well suited for weak signal
reception. I know that a Yagi can do very well in this regard, but
its the art of it that I'm interested in, and as far as I can see,
it's almost an lost aspect of HAM radio nowadays.

Does anybody remember these things?

73's
Rob

John Ferrell W8CCW


What if all the wires are not the same length. I know my friends were able
to cover all of 75/80 without retuning but this may have been because of the
losses in the steel wire they were using..