Re: NEC-LIST: Modeling loops

Roy,

I ran MININEC Professional for a square loop with
a radius about equal to AWG 12 and found resonance
at a perimeter of P(ft) = 1045/f(MHz). I suspect
the result is radius dependent. The thumb rule you
cite may be for an infinitely thin wire, possibly
based on a statics solution. I ran a square loop
for radii of 1E-06, 1E-09, and 1E-20 ft. MININEC
Professional response for a square loop is flat
with radii of 1E-06 ft or smaller. I did not carry
it any further than 1E-20. The best result obtained
is P = 1037/f. By the way, for the record, MININEC
Professional has an improved formulation over previous
versions of MININEC -- the use of very short segments
at the corners is not required.

Best Regards,

JIM Logan

At 01:15 PM 12/3/96 -0800, you wrote:
>Firmly-entrenched lore gives the perimeter of a square loop at resonance to be
>1005/f(MHz) feet. NEC-2, NEC-4, and MININEC all agree quite closely with each
>other, but none show this value. (MININEC requires very short segments at the
>corners for this analysis.) For AWG 12-16 wire at 10 MHz, the programs show a
>free space resonant perimeter length of 1031-1034/f. This of course changes
with
>proximity to ground and loop shape, but I couldn't find any reasonable
>configuration which would bring the model resonant perimeter lower than about
>1020/f.
>
>While two or three percent is good accuracy, an error that size is more than
>enough to significantly affect the pattern of a parasitic array if the error
>occurs in a parasitic element.
>
>Does anyone know of any good measurements of the impedance of a nominally full
>wavelength perimeter loop, or of the pattern of a quad or similar parasitic
>array of loops, for comparison to NEC results?
>
>Thanks!
>
>Roy Lewallen
>
>
>
>
Received on Thu Dec 05 1996 - 15:16:00 EST