On Sun, 25 Jan 2004 20:33:59 GMT, gecwhite wrote:

As one who makes his living in the RF field, I say you are flatly
wrong. Distortion is an acute matter of concern in modern digital
radios that require high linearity. For example, massive amounts of
money are spent in feedforward power amplifiers for cell base stations.
For example, PA non-linearity is one of the major limiting factors in
WLAN OFDM transmitter link budgets (52 subcarriers and up to 64-QAM on
each subcarrier). And it goes on and on.

My posts have been in accordance with "the generalities" of dB's
and dBm's and was prompted in response to a particular posting.
With this in mind, it is possible to find exceptions within disciplines.
CATV was merely one of these. So is yours. You get no argument
from me in this respect.



A bandpass filter could be used to reduce out of band signals, sometimes
lowpass, even less frequently, highpass. This would be especially the case for
RF amplifiers, broadband RF amps and to some extent transmitters etc.

BP filters can't remove odd-order intermod products, and no one finds
sine waves, by themselves, particularly interesting, even music
listeners. Because CATV equipment is so wide-banded, even-order
distortion is also major concern. That is why balanced amplifiers
dominate that field.

No one has argued or proposed that they do.
Read what I have said about CATV.

However, we are biginning to stray from the original post. It was your
second-line statement, above, to which I was makeing an exception

I agree. They use dB as a relative level, ...

A dB, by itself, it always just "relative," by definition. It is a
ratio and nothing else.

No one has said otherwise. Thanks


...when it comes to specifying
distortion. When I wrote "distortion in -dB(power)", I ment the
distortion power *relative* to the signal power.

Which I believe should almost go without needing to say so.
Hmmm. I checked my posts.
I believe you may be quoting someone else.


CATV's are outside my experience. Nor did I particularly single them out for
distinction. My point was that most people in the side industries (non-audio)
which you cited, still use and properly so, dB's as a relative term...

It can't be used in any way _but_ relative, because no absolute
reference point can be gleaned from it in the absence of other
information!
Precisely.
So we agree even though my points are understated rather than emphatic.


... and dBm's
when implying a 'standard' level.

Sure it is a "standard" notation, but more importantly it refers to an
_absolute_ power level.
Precisely.
So we agree even though my points are understated rather than emphatic.


Now. This really ends my interest in this thread.