On Tue, 27 Apr 2010 21:04:15 -0700, Jeff Liebermann
wrote:

Example: Can someone tell me which line number offers the meaning for
Diversity?

A link to the Wikipedia page would probably have been sufficient:
http://en.wikipedia.org/wiki/Diversity_scheme
The problem is that NONE of the diversity schemes mentioned in the
Wikipedia article apply to the single antenna example under
discussion.

So, this is an example of a "straw man" argument (not yours, Tom's): a
solution to a problem that is undefined. There are, thus, many
solutions that none can refute and why Tom's is the sine qua non is
built on a foundation of sand.

In my never humble opinion, there's no way to provide any
form of diversity reception improvement with a single antenna, unless
one also has two feeds, going to two different receivers, and ending
in either a decision switch, or some form of intelligent combiner.

Well, to Tom's credit, there is ample discussion of that - but that
discussion does not answer the question, which means there is no way
to test for validity.

I am not interested in interpretations of Tom, nor
abstractions culled together from disjoint statements.

How about my definition?

Sorry, Jeff, but unless you are the author of the Wikipedia reference,
I cannot answer your question.

No matter which scheme is used, a diversity
reception scheme must demonstrate an improvement in availability, BER,
or SNR over a single antenna, or it's not really diversity.

I presume the statement above is your definition. Reducing S+N/N
satisfies what you call diversity and provides an example of a
self-referential definition in that you appeal to with "SNR." Self
referential definitions are logical nulls. In other words, does
increasing capture area qualify as diversity for a single antenna? If
so, diversity means less noise or a better signal in comparison. What
is diverse about ordinary directivity? What is the profit in having
two words describe the same thing?

Even with an informal presumption of the meaning of diversity, we can
both agree that diversity is not also directivity.

Or perhaps it is that, and with one characteristic more. This returns
us to the question with some refinement: what is diversity in the face
of directivity? I have a hunch directivity is a distraction, but that
returns us to the original question.

I want to know
where (literally, not figuratively) Tom defines what Diversity is.

He doesn't.

I didn't think so and I was asking because I didn't consider it worth
the effort to search for something so obscured by the baggage of
peripheral discussion.

I'm rather confused as to his "stereo diversity" which I guess uses
the listeners ears and brain as the decision switch or decoder. I
think he might be referring to a direct conversion receiver where one
channel is quadrature leading and the other is quadrature lagging,
resulting in a stereo-like effect.

I will admit this was my interpretation too. Strange how you have to
sift the diamonds out of the horse-****. I had worked in this field
and built quadrature detectors 40 years ago to the same ends as you
describe. Analog TV color detection had been doing it for at least 20
years before that. I suppose there is a metaphor of diversity there,
but it came with the subject of quadrature detection as a solution,
not as a recent invention.

The quad detector is a direct conversion receiver as you say.

For other readers:
The signal is split through two channels each mixed with the same
base-band source, with one feed of the source shifted 90 degrees for
one channel. I suppose here we could drop the input splitter and
simply feed in two antenna drives. The separate mixer outputs feed
separate headphone elements (the classic application way back then)
and the brain perceives the signal as existing in a literal 2D
(binaural) space. The consequence of this perception is a heightened
ability to discriminate one signal from the rest within the bandpass
of reception. The bandpass is perceived as a physical left-to-right
space and because the classic application was through headphones, this
space was also between the ears. For the modern reader, this was like
having a spectrum analyzer in your head.

This is the classic situation of being able to listen to one
conversation in a crowded room full of speakers (the cocktail party
problem) without becoming overwhelmed by overlapping dialog. A simple
test is when you tune to the signal of interest, any off-frequency
signals are perceived as inhabiting this 2D space at a literal
off-center. As no two transmissions occupy the exact same frequency
(Tom explicitly mentions errors as small as a quarter Hertz), then
they lose being at the center of attention. The brain supplies a huge
computational engine that computers have yet to match.

The topic of Quad detection is cool in its own right, but I don't see
how tarting it up with the discussion of Diversity (especially when
the term is one of dim provenance) really adds anything. Quad
detection read more like window dressing than the clincher to the
topic at hand.

73's
Richard Clark, KB7QHC