Corrections:

I apologize, and misinterpreted my scribbled notes. The conclusion is
the same, but some of the quoted numbers are a little off. Here are the
correct ones.

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And suppose that these are exactly what our measurement of the cable
said. We measure 21 + j20 at the input end, and conclude that the
impedance of the antenna is 322 - j105 ohms.

But suppose the measurement at the input end was inaccurate by about 5%,
and that the actual input end Z was 22 + j21. Then the load Z is 273 -
j125, about 15% off in R, 20% in X. . .

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Roy Lewallen wrote:

And suppose that these are exactly what our measurement of the cable
said. We measure 21 + j20 at the input end, and conclude that the
impedance of the antenna is 374 - j84 ohms.

But suppose the measurement at the input end was inaccurate by about 5%,
and that the actual input end Z was 21 + j20. Then the load Z is 322 -
j105, about 15% off in R, 25% in Z. . .