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Frank wrote:
.... Using NEC 2 I found out, the hard way, that maximum pick-up takes place off the ends of the loop. Given these constraints: With a field strength of 5.5 V/m, the voltage across the 50 Ohm resistor is 0.091 V RMS, or an antenna factor of 35.1 dB. Within 0.4 dB of Owen's results. I have modified my EZNEC model to irrradiate the loop from an exciter dipole at some distance. I have tried it with the exciter at 100m and 200m distance, I get AF=35.69 and 35.72 dB respectively (against 36.1 from the Mathcad model). I note that if you report on the so called near field values too close to the loop, the results are effected by the loop. I note that the Matchcad model estimates the inductance slightly higher than EzNEC, and others have suggested to me that the Lw term in the Matchcad model is a double up, that the Ll term fully accounts for the inductance of the loop. Removal of the Lw term results in an AF of 35.8dB, which is closer to the EzNEC prediction. Has anyone views of whether Lw should not be included? The currents in my model vary slightly, here is the current report: Frequency = 7.1 MHz Wire No. 1: Segment Conn Magnitude (A.) Phase (Deg.) 1 W4E2 4.0E-6 -137.0 2 4.0E-6 -137.7 3 4.0E-6 -138.1 4 4.0E-6 -138.4 5 4.0E-6 -138.5 6 4.0E-6 -138.4 7 4.0E-6 -138.1 8 4.0E-6 -137.5 9 W2E1 4.0E-6 -136.8 Wire No. 2: Segment Conn Magnitude (A.) Phase (Deg.) 1 W1E2 4.1E-6 -136.0 2 4.1E-6 -135.1 3 4.1E-6 -134.2 4 4.1E-6 -133.4 5 4.2E-6 -132.5 6 4.2E-6 -131.7 7 4.2E-6 -130.8 8 4.3E-6 -130.0 9 W3E1 4.3E-6 -129.2 Wire No. 3: Segment Conn Magnitude (A.) Phase (Deg.) 1 W2E2 4.3E-6 -128.4 2 4.3E-6 -127.8 3 4.4E-6 -127.4 4 4.4E-6 -127.2 5 4.4E-6 -127.1 6 4.4E-6 -127.2 7 4.4E-6 -127.4 8 4.3E-6 -127.9 9 W4E1 4.3E-6 -128.5 Wire No. 4: Segment Conn Magnitude (A.) Phase (Deg.) 1 W3E2 4.3E-6 -129.3 2 4.3E-6 -130.1 3 4.2E-6 -130.9 4 4.2E-6 -131.8 5 4.2E-6 -132.6 6 4.1E-6 -133.5 7 4.1E-6 -134.3 8 4.1E-6 -135.2 9 W1E1 4.1E-6 -136.1 Owen |
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