Thanks Roy.

I note you observe similar variation in usage as I note.

Yes, consistency in an application is more important than a common meaning
of the term, but a common meaning of the term assists simpler
communication.

Regarding say, a base fed folded monopole and efficiency calculations, if
the connection to ground is though of as having some actual value Rg, since
the current flowing in Rg is twice the feedpoint current, consistent
development of the circuit model will reveal the correct efficiency as:

Rr/(Rr+2Rg)

where Rr is the sum of power in the far field divided by feed point current
squared. You don't need to fudge Rr to get the result, proper allowance of
the power due to the actual current in Rg provides the correct result.

Kraus (Annennas for All Applications) effectively defines Rr as part of his
development of the concept of a pair of conductors transitioning from a
non-radiating transmission line to an antenna to free space radiation.

He does say "... the radiation resistance Rr, may be thought of as a
"virtual" resistance that does not exist physically but is a quantity
coupling the antenna to distant regions of space via a "virtual"
transmission line."

It is his use of "distant regions of space" that suggests in the case of
ground reflection, it is the remaining total power in distant free space
after lossy reflection that is used to calculate Rr. The power lost in
reflection would be a component of feed point R, but not Rr.

He also states a little earlier "... the antenna appears to the
transmission line as a resistance, Rr, called the *radiation resistance*.
It is not related to any in the antenna itself, but a resistance coupled to
the from space to the antenna terminals." This seems fairly clear to me
that he defines radiation resistance to be at the transmission line /
antenna interface.

Both of these statements by Kraus are simple, but would seem to be capable
of application to real antenna systems. I can't immediately think of
exceptions (game on???).

In Kraus's language, ground reflections might reasonable be considered part
of the 'antenna' since they influence its pattern and loss, and loss in the
ground reflections is due to resistance "in the 'antenna' itself" and so
excluded from Rr.

Is there anything in Kraus's statements that is wrong, or my
interpretatiohn of them.

Owen