On Sun, 2 May 2010 21:44:30 -0500, (Richard
Harrison) wrote:

Jeff Liebermann wrote:
"In my never humble opinion, there`s no way to provide any form of
diversity reception improvement with a single antenna, unless one also
uses two feeds, going to different receivers, and ending in either a
decision awitch or an intelligent combiner."

That is my experience too. Space diversity requires 2 or more antennas
and receivers. One antenna can serve separate receivers which are
connected to cross-polarized feeds using a single reflector for
polarization diversity.
Or, multiple receivers can be used on a single receiving antenna, but
transmission of more than one copy of the desired signal is required,
This is how frequency diversity is usually achieved. Two copies of the
same program may be modulated on the same carrier if it is shown that
the medium treats the sidebands differently so that when one is treated
badly the other may be solid. I`ve seen this done with selection of
upper or lower sideband from a double sideband transmission.

Best regards, Richard harrison, KB5WZI

Thanks. It's an unusual experience when someone actually agrees with
me.

Part of the problem is that HF and microwave diversity have different
purposes and therefore different methods. I'll try to describe some
of these (until the epoxy dries and is safe to handle).

For example, the common Wi-Fi 2.4Ghz access point, uses diversity to
mitigate the effects of frequency selective fading. With two
antennas, one receiver, and a PIN diode switch, the access point
normally has one MAIN antenna selected. However, when the error rate
climbs to the point where the MAIN antenna is hearing garbage, the PIN
switch selects the AUX antenna in the hope of an improvement. With
frequency selective fading, the MAIN antenna could easily be sitting
at a location, where the direct and incident paths from the client
radio are 180 degrees otto phase, and therefore would cancel. By
switching to the AUX antenna, the assumption is that it is not located
in a place where the signals cancel.
http://www.cisco.com/en/US/tech/tk722/tk809/technologies_tech_note09186a008019f646.shtml
http://www.commsdesign.com/design_corner/showArticle.jhtml?articleID=16501888
http://www.commsdesign.com/design_corner/showArticle.jhtml?articleID=16500279

For VHF/UHF, a form of diversity that is very commonly used is a
receiver voting system. These are heavily used by municipal services
to cover wide areas with HT's. The HT can easily hear a single
central dispatch transmitter, but the return TX power is limited,
requiring multiple receivers at difference geographic locations to
cover a city or county. For such systems, remote receivers are
located at various locations. The backhaul returns the audio and data
to a central location, where a voting system equalizes the backhaul
delays, determines the best SNR, and provides the dispatcher with the
best possible receiver audio or data. There are various patented
schemes to make the SNR selection. While not normally considered a
diversity reception system, I consider it to be a form of diversity.
http://www.repeater-builder.com/tech-info/votingcomparators.html

For HF, the problem is fading caused by atmospheric and ionospheric
phenomenon. There are several types of fades (flat, frequency
selective, multipath, Faraday rotation polarization change,
absorptive, fast, slow, etc). Some of these are detailed in:
http://en.wikipedia.org/wiki/Fading
The assumption is that for most (not all) types of HF fading,
geographic separation of the antennas will result in one of the two
antennas being in a location where the fade is minimal. In order to
utilize this advantage, some manner of voting system needs to be
implemented to decide which antenna is best. This is usually done
with two receivers, but can be done with a single receiver and an
antenna switch, if one is willing to tolerate some data loss when the
receiver is switched to the wrong antenna.
http://www.navy-radio.com/rcvr-div.htm
(Also search for "dual diversity HF reception")

Locating the two HF antennas at a single location has some benefits
when dealing with polarization diversity, but is generally a loser
when dealing with most of the others, where both antennas (and both
polarizations) are likely to simultaneously experience the same fade
mechanism. For such contrivances, I suspect it might be equally
effective to setup the HF antenna for circular polarization.

Ok... the epoxy is sorta dry.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Apr 27, 7:22*pm, Art Unwin wrote:
Tom Rauch W8JI has added to his home page a discussion about diversity
antennas
As a known authority on antennas he presents interesting insights
regarding my
diversity antenna *where I show computer results of different polarity
gains.
His knowledge of antennas is much greater than mine, so if any have
shown an interest in my antenna design it would be worth while to read
Tom's aproach as to what exactly is happening and why
Regards
Art Unwin KB9MZ

Sly old Art Unwin alludes to his antenna design and initiates a long
technical thread which talks about anything but an Unwin antenna. And
how useful is the discussion to the average reader of r.r.a.a.?

On Wed, 28 Apr 2010 10:11:51 -0700 (PDT), Bill wrote:

how useful is the discussion to the average reader of r.r.a.a.?

Hi Bill,

Well, diversity antenna work is quite useful to the average reader - I
suppose (they haven't actually clamored for the discussion or
embroiled themselves in the topic, but you did couch this in terms of
"readers").

Unfortunately, if we divorced the two authors who fail to offer what
Diversity means, apart from what is already accepted in convention,
then we remove the entertainment value and "readership" would likely
decline.

A paradox.

73's
Richard Clark, KB7QHC

Richard Clark wrote:
On Wed, 28 Apr 2010 10:11:51 -0700 (PDT), Bill wrote:

how useful is the discussion to the average reader of r.r.a.a.?

Hi Bill,

Well, diversity antenna work is quite useful to the average reader - I
suppose (they haven't actually clamored for the discussion or
embroiled themselves in the topic, but you did couch this in terms of
"readers").

Sure, at least in a practical sense. I make use of diversity receivers
in wireless microphone work.

While these are used at UHF frequencies rather than HF, our problems are
more multipath, maybe picket fencing a bit.

So while I know better than to get into the definitions of diversity
antennas, given my meager abilities, my guess is that if one antenna
worked better than two - or merely worked at all, we'd be using just one.

Tom's pseudo stereo looks suspiciously like a wetware version of my
wireless systems,only that they vote, whereas his signal levels are too
low for that, so he does it in his head.


Unfortunately, if we divorced the two authors who fail to offer what
Diversity means, apart from what is already accepted in convention,
then we remove the entertainment value and "readership" would likely
decline.

That is for certain.

A paradox.

One of my favorite words.

On Apr 28, 6:45*pm, Michael Coslo wrote:
Richard Clark wrote:
On Wed, 28 Apr 2010 10:11:51 -0700 (PDT), Bill wrote:

how useful is the discussion to the average reader of r.r.a.a.?

Hi Bill,

Well, diversity antenna work is quite useful to the average reader - I
suppose (they haven't actually clamored for the discussion or
embroiled themselves in the topic, but you did couch this in terms of
"readers").

Sure, at least in a practical sense. I make use of diversity receivers
in wireless microphone work.

While these are used at UHF frequencies rather than HF, our problems are
more multipath, maybe picket fencing a bit.

So while I know better than to get into the definitions of diversity
antennas, given my meager abilities, *my guess is that if one antenna
worked better than two - or merely worked at all, we'd be using just one.

Tom's pseudo stereo looks suspiciously like a wetware version of my
wireless systems,only that they vote, whereas his signal levels are too
low for that, so he does it in his head.

Unfortunately, if we divorced the two authors who fail to offer what
Diversity means, apart from what is already accepted in convention,
then we remove the entertainment value and "readership" would likely
decline.

That is for certain.

A paradox.

One of my favorite words.

if the pseudo stereo is derived from 2 different antennas then you
have diversity reception where the separate antennas provide different
signals that may fade at different times due to polarization changes
or incident angle changes... that is what tom was driving at as a
useful diversity system, albeit at the expense of more complex
receiver hardware.

when you take a single rf signal and split it through different
receive processors to shift the phase, or do different sidebands, or
just run through different high/low pass audio filters, you don't
really have diversity, you have some kind of a processing system that
makes it easier for your brain or some other decoder to sort out the
signal from the noise. I played with some simple ones years ago and
they can provide interesting effects that can make sorting out signals
in pileups easier, or maybe pulling signals out of the noise a bit
easier, but none of them will really prevent the multipath, arrival
angle, or polarization fading. that is where tom was trying to point
out that any way you combine the rf from two antennas into one you
lose the advantages of the diversity of the antennas.

On Wed, 28 Apr 2010 15:51:35 -0700 (PDT), K1TTT
wrote:

that any way you combine the rf from two antennas into one you
lose the advantages of the diversity of the antennas.

I saw that bold statement as well, and then it was treated to a fog of
support.

At some point, the RF from two antennas must combine by the time it
hits our ears. That, or diversity reception means two people
listening to two sources and then matching notes - which means the RF
from the two antennas combine on the final page draft.

So, let me put this forward.
Two antennas
feeding two separate RF chain amplifiers
both chains mixed from a single LO
two separate mixers into IF chain amplifiers
--- somewhere they have to combine ----
two IFs into two detectors
two detectors into two separate audio chain amps
each audio chain driving a speaker element.

I have (gasp!) interpolated, interpreted, simply guessed, guessed
wrong, guessed right, about this single LO. Maybe it was in the
detector at the end of the IF chain. Whatever.

So, with this duality extending from antenna(s) to speaker(s), is the
prohibition against combining the RF from two antennas merely a
syllogism?

OK, backing up that chain to the concept of two separate RF chain
amplifiers. Lets just call it one RF chain amplifier or no RF
amplifiers and straight to a mixer. Is the prohibition at the
combining of RF from two antennas located at the mixer input? No
parallel connection?

This is getting ugly because it is not about diversity, and it is not
about antennas.

73's
Richard Clark, KB7QHC

On Apr 28, 5:51*pm, K1TTT wrote:
On Apr 28, 6:45*pm, Michael Coslo wrote:



Richard Clark wrote:
On Wed, 28 Apr 2010 10:11:51 -0700 (PDT), Bill wrote:

how useful is the discussion to the average reader of r.r.a.a.?

Hi Bill,

Well, diversity antenna work is quite useful to the average reader - I
suppose (they haven't actually clamored for the discussion or
embroiled themselves in the topic, but you did couch this in terms of
"readers").

Sure, at least in a practical sense. I make use of diversity receivers
in wireless microphone work.

While these are used at UHF frequencies rather than HF, our problems are
more multipath, maybe picket fencing a bit.

So while I know better than to get into the definitions of diversity
antennas, given my meager abilities, *my guess is that if one antenna
worked better than two - or merely worked at all, we'd be using just one.

Tom's pseudo stereo looks suspiciously like a wetware version of my
wireless systems,only that they vote, whereas his signal levels are too
low for that, so he does it in his head.

Unfortunately, if we divorced the two authors who fail to offer what
Diversity means, apart from what is already accepted in convention,
then we remove the entertainment value and "readership" would likely
decline.

That is for certain.

A paradox.

One of my favorite words.

if the pseudo stereo is derived from 2 different antennas then you
have diversity reception where the separate antennas provide different
signals that may fade at different times due to polarization changes
or incident angle changes... that is what tom was driving at as a
useful diversity system, albeit at the expense of more complex
receiver hardware.

when you take a single rf signal and split it through different
receive processors to shift the phase, or do different sidebands, or
just run through different high/low pass audio filters, you don't
really have diversity, you have some kind of a processing system that
makes it easier for your brain or some other decoder to sort out the
signal from the noise. *I played with some simple ones years ago and
they can provide interesting effects that can make sorting out signals
in pileups easier, or maybe pulling signals out of the noise a bit
easier, but none of them will really prevent the multipath, arrival
angle, or polarization fading. *that is where tom was trying to point
out that any way you combine the rf from two antennas into one you
lose the advantages of the diversity of the antennas.

Tom
From my viewpoint which may well be unconventional,
may I point out that both elements as well as the array as a whole is
resonant and in equilibrium.
Thus in reality, you have two separate antennas that are additive and
go to the same receiver.
The receiver uses the addition of the two current flows or two
separate flows thus picking up both linear and non linear signals. So
I would suggest that the antenna is therefore sensitive to both .
phases( ie in phase and out of phase fields).
Ww8ji is of the opinion that the program is in error by virtue of the
statement it makes since it is unable to print the truth but doesn't
provide evidence of same.I believe he is looking at an array that is
not in equilibrium to arrive at his viewpoint.
Both elements pick up the same message with one having a delay in
time due to phase change regardles of what created it, deflection or
other wise. This is no different to viewing both elements as
mechanically vibrating and because the array as a whole is in
equilibrium both will vibrate in unison
Regards
Art

K1TTT wrote:
On Apr 28, 6:45 pm, Michael Coslo wrote:
Richard Clark wrote:
On Wed, 28 Apr 2010 10:11:51 -0700 (PDT), Bill wrote:
how useful is the discussion to the average reader of r.r.a.a.?
Hi Bill,
Well, diversity antenna work is quite useful to the average reader - I
suppose (they haven't actually clamored for the discussion or
embroiled themselves in the topic, but you did couch this in terms of
"readers").
Sure, at least in a practical sense. I make use of diversity receivers
in wireless microphone work.

While these are used at UHF frequencies rather than HF, our problems are
more multipath, maybe picket fencing a bit.

So while I know better than to get into the definitions of diversity
antennas, given my meager abilities, my guess is that if one antenna
worked better than two - or merely worked at all, we'd be using just one.

Tom's pseudo stereo looks suspiciously like a wetware version of my
wireless systems,only that they vote, whereas his signal levels are too
low for that, so he does it in his head.

Unfortunately, if we divorced the two authors who fail to offer what
Diversity means, apart from what is already accepted in convention,
then we remove the entertainment value and "readership" would likely
decline.
That is for certain.

A paradox.
One of my favorite words.

if the pseudo stereo is derived from 2 different antennas then you
have diversity reception where the separate antennas provide different
signals that may fade at different times due to polarization changes
or incident angle changes... that is what tom was driving at as a
useful diversity system, albeit at the expense of more complex
receiver hardware.

Yeah, I think I agree with Tom's practical experience/experiment. I
certainly do not think that one antenna is going to do this diversity,
because if it would, it means that there is no need for any of the
diversity systems we know about today, with double antennas, voting
and/or dual receivers.

Richard's concerns are for the definition, which I think in Art's case,
is probably important.


when you take a single rf signal and split it through different
receive processors to shift the phase, or do different sidebands, or
just run through different high/low pass audio filters, you don't
really have diversity, you have some kind of a processing system that
makes it easier for your brain or some other decoder to sort out the
signal from the noise. I played with some simple ones years ago

side foray here. Did you try binaural receivers? I've heard of them,
never had a chance to listen to one.


and
they can provide interesting effects that can make sorting out signals
in pileups easier, or maybe pulling signals out of the noise a bit
easier, but none of them will really prevent the multipath, arrival
angle, or polarization fading. that is where tom was trying to point
out that any way you combine the rf from two antennas into one you
lose the advantages of the diversity of the antennas.

I agree. One of the important factors as far as I know is that the
antennas have to be in two different spots, and although I haven't
measured, (I will now that I'm really interested) I'll bet that the best
performance comes at a distance that is well related to the wavelength.
Which is to say the picket fencing I hear on a mobile two meter signal
might allow me to determine his velocity by knowing the frequency of the
picket, the frequency of the transmission, with a likely but small error
via Doppler shift.

But aside from that little foray, I have no doubt that the effects that
call for diversity antennas/receivers also call for some physical
separation of separate antennas.

- 73 de Mike N3LI -

Bill wrote:
On Apr 27, 7:22 pm, Art Unwin wrote:
Tom Rauch W8JI has added to his home page a discussion about diversity
antennas
As a known authority on antennas he presents interesting insights
regarding my
diversity antenna where I show computer results of different polarity
gains.
His knowledge of antennas is much greater than mine, so if any have
shown an interest in my antenna design it would be worth while to read
Tom's aproach as to what exactly is happening and why
Regards
Art Unwin KB9MZ

Sly old Art Unwin alludes to his antenna design and initiates a long
technical thread which talks about anything but an Unwin antenna. And
how useful is the discussion to the average reader of r.r.a.a.?

Not only useful, but more practical to boot.

- 73 de Mike N3LI -

On 4/28/2010 12:11 PM, Bill wrote:
On Apr 27, 7:22 pm, Art wrote:
Tom Rauch W8JI has added to his home page a discussion about diversity
antennas
As a known authority on antennas he presents interesting insights
regarding my
diversity antenna where I show computer results of different polarity
gains.
His knowledge of antennas is much greater than mine, so if any have
shown an interest in my antenna design it would be worth while to read
Tom's aproach as to what exactly is happening and why
Regards
Art Unwin KB9MZ

Sly old Art Unwin alludes to his antenna design and initiates a long
technical thread which talks about anything but an Unwin antenna. And
how useful is the discussion to the average reader of r.r.a.a.?

It's the amusing part. Totally useless technically, but often comprises
nearly 100% of the traffic on this group for days or weeks.

tom
K0TAR