Total posts : 45366
I wonder if Rich now agrees with me that the power gain of a system of two half-wave dipoles is the same as the power gain of a system of two quarter-wave monopoles above ground. If he agrees with that, he agrees that there is a reciprocity failure of the receiving monopole when receiving a groundwave. There simply is no way around that. If Rich still does not agree with that, I suggest now, as I did in previous posts, that he get his NEC program working, and prove this for himself. In Rich’s previous posts, he cited NEC among the authorities he used against my assertions. It now looks like NEC is on my side. I submit NEC as the “authoritative reference” that Rich is looking for.
(I was composing my reply to Rich offline when the previous comment was posted, so I missed it. I am glad that this discussion has a readership. I see that the read count for this thread is respectable. This subject is relevant to Part 15 AM because it applies to AM radio reception. It surprises me how much consternation this subject causes, not only between Rich and myself, but also between other RF engineers.)
The reciprocity failure of a monopole above ground receiving a groundwave is mathematically proved by comparing the system power gain of two parallel half-wave dipoles at the same height in free space to that of two parallel quarter-wave monopoles over a ground plane. If the power gains of these two antenna systems are the same, then what I am saying has been proved. QED.
Since the reciprocity failure with two monopoles has been proved, the same reciprocity failure applies to a single receiving monopole above ground. Also, since the reciprocity failure has been proved, quotes from authors who did not mention this exception to the principle of reciprocity, for whatever reason, are not relevant.
As for Rich’s question about the elevation of the incident radiation at which the reciprocity failure applies, as I said in previous posts, it applies only to the surface wave traveling along the ground plane (groundwaves). It does not apply to waves that are reflected from the ground plane (sky waves). For that reason, plots of the receiver gain and the transmitter gain appear identical, because the reciprocity failure applies only to one ray, which can be missed on the plot. This one ray is the groundwave, which is a very important component of the signals transmitted in medium-wave radio communications.