"Richard Clark" wrote in message
...
On Tue, 25 May 2004 11:23:03 -0500, "Richard Fry"
wrote:
This topic deserves more attention than it will get from its previous
placement deep in some recent threads.
Below is a quote
Which is a creationist-model of negative definition.

This is poor substitute for expressing a simple complex value derived
from actual measurement. The methods for accomplishing this are rote
material practiced by designers every day. The quality of their
product is in proportion to the accuracy of their determination.
73's
Richard Clark, KB7QHC

Side Comment:

Unfortunately, Richard Clark, the essence of your comment is completely
lost on me. I haven't the faintest idea what you mean. Are you criticizing
the quote or supporting it? Whatever...



Real content:

The quote posted by Richard Fry certainly explains well what we call
"Transmitter IM'" (the PA is a mixer and Tx frequencies mix producing other
signals). In the cellular telephone base station transmitter we have up to
20 transmitters on one antenna. In this case the IM is much more serious
because the power of the undesirable transmitter is not from a near antenna,
but a transmitter directly connected to the same antenna. Circulators in
each transmitter output are required to reduce the IM to acceptable levels
by diverting the unwanted TX signals to a load instead of the PA device..

I believe his intent (I'm guessing) is to show an authoritative report
that the output Z of a power amplifier is not equal to the load or
transmission line impedance, right?



As I stated before (with spelling corrected):

Get this MPT theorem blockage out of your minds... It is a synthetic
restriction.
The "maximum power theorem" (ZL=Zs) ONLY applies to ONE special case, NOT
all cases. That case is where the source's output power (or if you like
current) capability is limited ONLY by the two resistances (source and
load). That is, the
case is when the source can put out all the power needed by these resistors
and no other internal limit dominates. A common circuit can be shown to
give maximum power at other than Zs=ZL (apparently violating the above
referred-to theorem). There are things other than these resistances that
limit the output power of a practical source.



I add... In fact, in that quote, he comments that a low source impedance is
what makes for higher (50%) efficiency.


--
Steve N, K,9;d, c. i My email has no u's.