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
PA3DJS
www.tetech.nl
without abc, PM will reach me.