Loop Calculator not in agreement with Implementation

Playing around with this on-line loop evaluation tool:

http://www.66pacific.com/calculators/small_tx_loop_calc.aspx

Immediately below are the outputs for a 17 gauge (.045 inch diameter) wire just under one-quarter wavelength in length for the 40 meter band loop antenna. Compare what the loop antenna calculator calculated versus what was seen for ‘actual real-world results’ shown further down:

Input Values:
Length of conductor:          32 feet
Diameter of conductor:        .045 inches (17 AWG)
Frequency:                    7 MHz

RESULTS:
Antenna efficiency:           21% (-6.9 dB below 100%)
Antenna bandwidth:            217 kHz
Tuning Capacitance:           149 pF (real world result = 24 pF)
Capacitor voltage:            702 volts RMS
Resonant circulating current: 4.60 A
Radiation resistance:         0.484 ohms (real world = 22.2)
Loss Resistance:              1.87 ohms
Inductance:                   3.46 microhenrys
Inductive Reactance:          152 ohms
Quality Factor (Q):           32.3
Distributed capacity:         26 pF
Antenna "circumference":      32 feet
Comments:

1) The specified conductor length of 32 feet is OK.

2) Conductor length should be between 17.0 and 34.1 feet at 
the specified frequency of 7 MHz.

3) For highest efficiency, the conductor length for a small 
transmitting loop antenna should be greater than 1/8 wavelength 
(greater than about 17.0 feet at the specified frequency of 7 
MHz). 

4) To avoid self-resonance, the conductor length for a small 
transmitting loop antenna should be less than 1/4 wavelength 
(less than about 34.1 feet at the specified frequency of 7 MHz).

– – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –

Below are the actual, real-world results obtained:

Antenna efficiency:           ~100% (on a par w/dipole)
Tuning capacitance:           24 pF 
Antenna bandwidth:            50 kHz 1.5:1, 110 kHz 3:1 
Radiation resistance:         22.2 ohms (fed w/transformer next to
                                         tuning capacitor)

AC and DC wire resistance calculations at 7 MHz:

Freq  Gauge  Wire  Len    DCR    ACR  Rrad  Ratio 
----- ------ ----- ---- ------- ----- ----  ----- 
7 MHz 17 ga.   Al   32'  0.265  2.452 22.5  9.17
7 MHz 10 ga.   Cu   32'  0.0318 0.835 22.5  26.9 

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