Meandering Antenna
 

On May 2, 5:56*am, Wimpie wrote:
On 2 mayo, 03:03, Art Unwin wrote:



On May 1, 8:10*am, Wimpie wrote:

On 1 mayo, 02:25, "VK2KC" wrote:

I was wondering if anyone had any experience of the Meandering Antenna or
Meandering Dipole, I have found an article in Pat Hawkers book but the
drawings are a bit hard to understand.
I have limited space and was considering building one for 7.1 mhz

Thanks
John

Hello,

I assume that you talk about meandering like the zig/zag pattern on a
viper or the pattern of a sidewinder. At other frequencies, yes I do
have.

Meandering increases the inductance per unit of length, so the
propagating wave slows down. This results in a reduction of resonant
length.

The zig/zag wire pieces do, however, not contribute to the far field

??????

This is news to me! Can you give me a reference ?
This clearly suggests that a twin wire formed in a closed circuit
helix cannot radiate in the far field when it clearly can regardless
of slow wave. If the dipole is clearly in equilibrium it cannot fail
to radiate but then everything depends on the presented aparture and
what medium it is operating under, such as a submarine at some depth
in sea water versus fresh water. I have found that such arrangements
start out at over 100 ohms and then gradually dampen down to 50 ohms
when you start to exceed twice the full wave length and it comprises
of a fully connected electrical wire circuit

A fine example of a meander circuit would be a fractal arranged in
full circuit form
Regards
Art

radiation. Given the same feed current, the meandered dipole radiates
less then the full HW one, so the radiation resistance goes down.
When your dipole length is about half of the full size length, feed
point impedance goes down with almost factor 4.

When you experience good VSWR in a center fed short meandered dipole,
you can be sure to have losses.

Best regards,

Wim
PA3DJSwww.tetech.nl
remove abc first in case of PM

Hello Art,

The zig/zag or square wave pattern is frequently used in planar
structures (PCB antennas or metal on plastic/paper).

Regarding your request for references, look at UHF (800-900 MHz) RFID
tags/transponders (TI, Alian, Rafsec, Feig, Deister, Sams, etc). They
use meandering to shorten the overall length of half wave resonating
structures. The radiaton pattern still matches that of a dipole, so
negligible radiation in axial direction. *As you are a ham also, it is
not too difficult to prove this yourself.

To get some axial sensitivity, the width of the structure should no
longer be overall length of structure.

Best regards,
Wim
PA3DJSwww.tetech.nl
without abc, PM will reach me.

Meander antennas are waht happens when you try to put a 80M antenna in
a 20M backyard.

Jimmie

Meandering Antenna
 

The zig/zag wire pieces do, however, not contribute to the far field
..
..
..
??????
This is news to me!
..
..
..
radiation. Given the same feed current, the meandered dipole radiates
less then the full HW one, so the radiation resistance goes down.
..
..
..
Meander antennas are waht happens when you try to put a 80M antenna in
a 20M backyard.
..
..
..
or 160M into a shoebox (connect the dots)
..
..
,

73's
Richard Clark, KB7QHC

Meandering Antenna
 

On May 2, 5:56*am, Wimpie wrote:
On 2 mayo, 03:03, Art Unwin wrote:



On May 1, 8:10*am, Wimpie wrote:

On 1 mayo, 02:25, "VK2KC" wrote:

I was wondering if anyone had any experience of the Meandering Antenna or
Meandering Dipole, I have found an article in Pat Hawkers book but the
drawings are a bit hard to understand.
I have limited space and was considering building one for 7.1 mhz

Thanks
John

Hello,

I assume that you talk about meandering like the zig/zag pattern on a
viper or the pattern of a sidewinder. At other frequencies, yes I do
have.

Meandering increases the inductance per unit of length, so the
propagating wave slows down. This results in a reduction of resonant
length.

The zig/zag wire pieces do, however, not contribute to the far field

??????

This is news to me! Can you give me a reference ?
This clearly suggests that a twin wire formed in a closed circuit
helix cannot radiate in the far field when it clearly can regardless
of slow wave. If the dipole is clearly in equilibrium it cannot fail
to radiate but then everything depends on the presented aparture and
what medium it is operating under, such as a submarine at some depth
in sea water versus fresh water. I have found that such arrangements
start out at over 100 ohms and then gradually dampen down to 50 ohms
when you start to exceed twice the full wave length and it comprises
of a fully connected electrical wire circuit

A fine example of a meander circuit would be a fractal arranged in
full circuit form
Regards
Art

radiation. Given the same feed current, the meandered dipole radiates
less then the full HW one, so the radiation resistance goes down.
When your dipole length is about half of the full size length, feed
point impedance goes down with almost factor 4.

When you experience good VSWR in a center fed short meandered dipole,
you can be sure to have losses.

Best regards,

Wim
PA3DJSwww.tetech.nl
remove abc first in case of PM

Hello Art,

The zig/zag or square wave pattern is frequently used in planar
structures (PCB antennas or metal on plastic/paper).

Regarding your request for references, look at UHF (800-900 MHz) RFID
tags/transponders (TI, Alian, Rafsec, Feig, Deister, Sams, etc). They
use meandering to shorten the overall length of half wave resonating
structures. The radiaton pattern still matches that of a dipole, so
negligible radiation in axial direction. *As you are a ham also, it is
not too difficult to prove this yourself.

To get some axial sensitivity, the width of the structure should no
longer be overall length of structure.

Best regards,
Wim
PA3DJSwww.tetech.nl
without abc, PM will reach me.

Meander antennas are waht happens when you try to put a 80M antenna in
a 20M backyard.

Jimmie

Meandering Antenna
 

Wim, PA3DJS wrote:
"The zig/zag pieces do, however, not contribute to the far field
radiation."

My take is slightly different. The complete antenna can be considered as
made up of infinitely small pieces, each of which contributes to a
wector sum at a distant point in the far field depending on the current
in the tiny segment and its position.

Best regards, Richard Harrison, KB5WZI

Meandering Antenna
 

Hello all,
I do appreciate the input, seems like its not such a good idea!

Just to clarify the actual construction details, the configuration would be
in a dipole.

The 1/4 lambda wire would be wound on a form which has slots cut into the
periphery of an insulator to accommodate the wire and the form would be
300mm (12") in diameter, the wire would be wound from top to bottom of the
form until all the wire is wound on the form. I envisage a 75mm (3") gap
between each slot, maybe more depending on the distance between the circular
insulators, around 1500mm (5 ft).

Hopefully you can picture what I was going to build!

John
VK2KC

There would be two of these and
"Richard Harrison" wrote in message
...
Wim, PA3DJS wrote:
"The zig/zag pieces do, however, not contribute to the far field
radiation."

My take is slightly different. The complete antenna can be considered as
made up of infinitely small pieces, each of which contributes to a
wector sum at a distant point in the far field depending on the current
in the tiny segment and its position.

Best regards, Richard Harrison, KB5WZI

Meandering Antenna
 

Richard Harrison wrote:
Wim, PA3DJS wrote:
"The zig/zag pieces do, however, not contribute to the far field
radiation."

My take is slightly different. The complete antenna can be considered as
made up of infinitely small pieces, each of which contributes to a
wector sum at a distant point in the far field depending on the current
in the tiny segment and its position.

Best regards, Richard Harrison, KB5WZI

And that's exactly how antenna modeling programs calculate the field --
except that the antenna is broken into a finite number of pieces rather
than an infinite number. As long as the current doesn't change much over
the length of one piece (or "segment" as called in antenna modeling),
the result is very accurate.

Roy Lewallen, W7EL

Meandering Antenna
 

"Roy Lewallen" wrote
...
Richard Harrison wrote:
Wim, PA3DJS wrote:
"The zig/zag pieces do, however, not contribute to the far field
radiation."

My take is slightly different. The complete antenna can be considered as
made up of infinitely small pieces, each of which contributes to a
wector sum at a distant point in the far field depending on the current
in the tiny segment and its position.

Best regards, Richard Harrison, KB5WZI

And that's exactly how antenna modeling programs calculate the field --
except that the antenna is broken into a finite number of pieces rather
than an infinite number. As long as the current doesn't change much over
the length of one piece (or "segment" as called in antenna modeling), the
result is very accurate.

In antennas are the standing waves. In a long wire antenna are many nodes.
Does anybody calculate the contribution from the nodes only?
S*

Meandering Antenna
 

On 3 mayo, 03:39, (Richard Harrison) wrote:
Wim, PA3DJS wrote:

"The zig/zag pieces do, however, not contribute to the far field
radiation."

My take is slightly different. The complete antenna can be considered as
made up of infinitely small pieces, each of which contributes to a
wector sum at a distant point in the far field depending on the current
in the tiny segment and its position.

Best regards, Richard Harrison, KB5WZI

Hello Richard,

Agree with the basic principle of (far) field calculation. Regarding
meandering or helical wound:

The longitudinal components reinforce each other, but the lateral
components (zig/zag parts), change direction each time. Therefore the
resultant field (vector sum) is negligible with respect to the field
from the longitudinal components.


Best regards,

Wim
PA3DJS
www.tetech.nl
remove abc first in case of PM

Meandering Antenna
 

On May 2, 9:39*pm, (Richard Harrison) wrote:
Wim, PA3DJS wrote:

"The zig/zag pieces do, however, not contribute to the far field
radiation."

My take is slightly different. The complete antenna can be considered as
made up of infinitely small pieces, each of which contributes to a
wector sum at a distant point in the far field depending on the current
in the tiny segment and its position.

Best regards, Richard Harrison, KB5WZI

Yep, that's why 160M antennas that fit in a shoebox don't work.

Jimmie

Meandering Antenna
 

Richard Clark wrote:
The zig/zag wire pieces do, however, not contribute to the far field
.
.
.
??????
This is news to me!
.
.
.
radiation. Given the same feed current, the meandered dipole radiates
less then the full HW one, so the radiation resistance goes down.
.
.
.
Meander antennas are waht happens when you try to put a 80M antenna in
a 20M backyard.
.
.
.
or 160M into a shoebox (connect the dots)

Twas a primitive antenna, a brutish thing, and went extinct long ago.
Meanderthals we called them.

- 73 de Mike N3LI -