Re: NEC-LIST: How Well Did the Wheeler Method Work?

In a message dated 4/23/99 2:23:52 PM Eastern Daylight Time, hagn_at_wdc.sri.com
writes:

<< Chip:
 
 I (and I believe others) are interested in how well the Wheeler
 (cap/can) method worked for your loops and dipoles. How closely did
 your modeling match the Wheeler-method measured values for Rl, the
 loss resistance?

 [snip!]
 
 P.S. I used a full-scale chicken-wire-on-wood model of a jeep in
 Thailand in 1967 to measure (with an ionospheric sounder--see my
 article in >>

Hi George--

I am always fascinated by such large-scale measurement efforts!
Co-ool!

Here's what we did:

1) Measure return loss without W.C.

2) Measure return loss WITH W.C.

3)ASSUME the difference amounts to the 'same side' of 50 ohms (some
may need to remember that return loss--at resonance-- corresponds to
an equivalent, but ambiguous impedance. For example: is a 10 dB return
loss 25 ohms or 100 ohms?)

Infer the radiative loss from the differential of 1) and 2)

Within the margin of error--typically 0.5-1 dB of return loss; 0.5 dB
of field strength--we found the W.C. did a good job of accounting for
the ohmic loss. I would have to convert and propagate the
uncertainties at this point, but my ballpark memory is 10-15%, perhaps
worst case 25% uncertainty between field strength inferred loss
(compared to a dipole) and W.C. inferred loss.

Doubtless there are those who do better; you would have trouble
describing my analog set up as state of the art!

73
Chip N1IR
Received on Sat Apr 24 1999 - 20:32:01 EDT