ha scritto nel messaggio
...

The total impedance as seen from the coaxial feeder is the sum of the
antenna impedance and the impedance of your (floating) ground (for
example some quarter wave radials). As input impedance of thin HW
radiator is high, many commercial antennas do not have radials. They
rely on the ( 1 kOhm) impedance of the screen of the coaxial feeder
or the mast/pole/roof structure, etc.

Ok. Have some right input now.. so, reading also the other posters (that
here i thanks for all the inputs...), i assume that:

- thin HW monopoles have high impedance;
- by the way, high impedance mean a Z transformer, or auto-transformer, that
match the ~1kOhm Z of the antenna to the 50 Ohm of feed line;
- radials are ininfluent or useless because HW monopole is a complete
resonant antenna;

What is not clear for me is "They rely on the ( 1 kOhm) impedance of the
screen of the coaxial feeder or the mast/pole/roof structure, etc."
What means? That because i have a complete resonant antenna the concept of
"ground" is only a concept of "Z in regard of what??" and because
pole/coax/mast present for sure a much lower Z (at monopole resonant
frequency) than the monopole itself, we (and the antenna) assume that
pole/coax/mast is "ground zero" for us ?

Sometimes your mast/pole or cable may show resonance that increases
the ground impedance as seen at the antenna base to a value not far
below 1 kOhm. This will lead to relative high RF current in mast/pole/
cable screen, and because of this, significant change in radiation
pattern.

And if i guess right in the precedent statement i wrote, in this case
(resonant mast/pole/feed line) i lose the "ground 0" reference and in this
case i do provide a low impedance reference to the antenna. Maybe, adding
some radial. But this is my guess, i'm not sure if is the right thing to do.

I have a document solely on HW monopoles he
http://www.tetech.nl/divers/HWmonopoleNL1.pdf.
It is in Dutch Language, but the comment in all graphs is in English
Language.
Read and appreciate for what i understand inside

I have one more (in pure newbie fashion ) question that i append directly
to Cecil post, but is very appreciated also a reply from all the readers of
this thread.

-.-. --.- , Cristiano, Italy