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I checked my (non-EZNEC) NEC model carefully, and don’t see any errors. The NEC average gain test shows it to be highly accurate. The gain, impedance and pattern of the transmit antenna are “textbook.”
But when I use my “other means” to calculate the power in a 73 ohm resistor at the center of the receive dipole for these conditions, that gives me about 170 mW, the same as you report.
So I don’t know what is going on with it at this point.