On Fri, 05 Nov 2004 18:51:01 -0700, Wes Stewart
wrote:
I believe it is your contention that loading to resonance with an
arbitrarily positioned inductor, or not loading at all, does not
affect the gain, and the radiation resistance is not the same as the
changing feedpoint resistance.

Hi Wes,

You show a unique power of observation. English is difficult for many
here.

I am in the other camp, along with Hansen, Devoldere, et. al. who say
that the current distribution does affect the radiation resistance
(and in the real world, the gain/efficiency).

You may have observed of late that recent a posting by me confirms
your understanding.

I hope you would agree that the normalized gain would be a good proxy
for efficiency.

I think "normalization" is were things went awry.

For example if we use the lossless 1/4 wavelength monopole over
perfect ground as a reference, then gain with respect to that (5.15
dBi) would be an indicator of efficiency.

I believe that you will agree that the efficiency can be determined
by:

Rr
eta = ------------- Eq.1
Rr + Rg + Rl

where Rr = radiation resistance
Rg = ground resistance
Rl = all other resistances (conductor, etc)

I think you would also agree that for the full-sized monopole over
perfect ground the feedpoint resistance of ~36 Ohm = radiation
resistance.

My results, all around, did not require perfection, and in fact,
nothing was resolvable through perfection if you would review that
recent post.

As an old (sorry [g]) metrologist, you're very familiar with
substitution, so let's set Rl = 0 (lossless case) and eta to 0.5 (-3
dB). Per Eq. 1, Rg = Rr.

This old metrologist found the very simple answer that eluded others
who simply took it on faith and stumbled for reason. My substitution
resolved the situation (aka the sniffer antenna which served admirably
to function as what you would appreciate as a "transfer standard").

So in our model, if I add a simulated ground resistance, Rg, that
reduces the gain by 3 dB, I have by substitution, determined the
radiation resistance.

Sure enough, if I add a 36 Ohm load at the bottom of the perfect 1/4
wave monopole, the gain drops to 2.14 dBi, and the feedpoint
resistance doubles.

I will let you try this with the other cases. I trust you will find
that the radiation resistance does decrease with shorter radiators
and/or lower loading points.

I hope I demonstrated your trust was merited.

I too I would appreciate other effort in kind to correct any
oversights I've made.

Each in our own way. Sorry to hear about your friend.

73's
Richard Clark, KB7QHC