Sorry to hack just a very short piece out of context, but it's pretty
fundamental to the whole issue. I'll try to comment on the rest later,
as time permits. . .

chuck wrote:

. . .

What is the required precision in SWR measurement needed to determine
resonant frequency?

. . .

There is no amount of precision which will make that possible.

The resonant frequency cannot be determined by measurement of SWR alone
(or more accurately, by an SWR meter reading), except in one very
special case: If the resistance at resonance is equal to the SWR meter's
characteristic impedance, then a reading of exactly 1:1 indicates
resonance at the SWR meter terminals. This is seldom the case for an
antenna or antenna system. In other words, if the SWR meter reads 1:1,
then the load it's connected to is 50 + j0, which is resonant (assuming
a 50 ohm SWR meter). There's no way to determine resonance with any
other reading or for any other resistance -- if the meter dips to, say
1.2:1 at some frequency, you can't know if resonance has occured at that
frequency unless you have some additional information.

Again, in practice, the point of minimum SWR meter reading is often, but
not always, very close to the point of resonance (at the SWR meter). And
again, there's seldom any need to determine resonance.

Roy Lewallen, W7EL

Ian White, G3SEK wrote:
Now if you measure the complex (R-X) impedance of an antenna across a
very wide range of frequencies, and plot it on the Smith chart, you will
typically find that it goes in a series of orbits around the chart.

For resonance not to occur at minimum SWR, the orbit must not be a
circle centered on the pure resistance line. The 'R' in the R+jX
impedance looking into my transmission line changes much faster
around resonance than does any SWR circle.
--
73, Cecil http://www.qsl.net/w5dxp