On Aug 13, 5:21*am, Ian Jackson
wrote:
In message
, Art
Unwin writes



On Aug 12, 3:42*pm, JIMMIE wrote:
On Aug 12, 3:21*pm, dave wrote:

Art Unwin wrote:

Use your own thread to ask for assistance on your question.
*Be prepared to answer why you are requesting this personal service .
I asked a question on this thread with respect to the main advantage
for hams that linear
polarization has over CP. I have no resistance to change if it can be
justified. I see
that it can pick up signals that linear antennas cannot hear because
of a 30 db attenuation
where as CP has only a 3 db attenuation!

Compared to what?

I thought he said earlirer that it had a 3 db gain

If you are horizontally polarized a vertical will be down 30db
theoretically than if it was horizontal and vica versa.

Where do you get 30dB from? 'Theoretically', it ought to be infinitely
down. In practice, because of reflections and things like that, it can
vary from 'a bit down' to 'a hell of a lot down'.

Correct.
A reference supplied earlier by Jeff in this thread stated "real
world
20db to 35 db" (You used the term "in practice) A manufacturer used
the figure 30 db when I followed thru on his other references which
also appeared to me as being reasonable



If the
radiator is set for CP transmissions other polarizations
will be down only 3 db theoretically.

This is correct. You are splitting the transmitter power - half power to
each orthogonal polarisation and, with a 90 degree phase shift,
producing a circularly polarised signal (instead of a 45 degree slant).

Seems obvious which is best to
have, except a lot of hams like long distance communication which
means you have to deal with reflections.
From this thread it is obvious to me that we are not sure, at this
point, what changes occur
when reflection comes about. Roy pointed out a "misconception" at
least to his findings but the fact is there is no list of known
changes that one can bank on for reflections of CP at least for the
present. If I am incorrect then please post your thoughts.

--
Ian