On Apr 30, 6:51*pm, Richard Clark wrote:
On Fri, 30 Apr 2010 16:20:48 -0700 (PDT), K1TTT
wrote:

i tried a few combinations of audio high pass/low pass and different
ssb in each ear. *there are some interesting effects you can get that
way that give you spatial effects as you tune across the band. *you
can get the feeling that the signals come in one ear and out the other
as you tune across them... interesting once you get used to it on cw,
but probably not much use on other modes.

RTTY might have a ping-pong game on acid effect. *

73's
Richard Clark, KB7QHC

Qrz forum has a new posting that states the USN
changed their antennas on the west coast to those tipped from the
horizontal for superior results. This is 60 years ago before the
advent of antenna computers. I would like to think that they saw the
advantages of using two vectors as opposed to just the single one for
gravity, which in a way confirms the diversity antenna shown on the
unwinantennas page which is sensitive to multi polarities. Ofcourse
many on this net will disagree in order to avoid change.
Cheers

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

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 May 1, 7:00*pm, Art Unwin wrote:
On Apr 30, 6:51*pm, Richard Clark wrote:

On Fri, 30 Apr 2010 16:20:48 -0700 (PDT), K1TTT
wrote:

i tried a few combinations of audio high pass/low pass and different
ssb in each ear. *there are some interesting effects you can get that
way that give you spatial effects as you tune across the band. *you
can get the feeling that the signals come in one ear and out the other
as you tune across them... interesting once you get used to it on cw,
but probably not much use on other modes.

RTTY might have a ping-pong game on acid effect. *

73's
Richard Clark, KB7QHC

Qrz forum has a new posting that states the USN
changed their antennas on the west coast to those tipped from the
horizontal for superior results. This is 60 years ago before the
advent of antenna computers. I would like to think that they saw the
advantages of using two vectors as opposed to just the single one for
gravity, which in a way confirms the diversity antenna shown on the
unwinantennas page which is sensitive to multi polarities. Ofcourse
many on this net will disagree in order to avoid change.
Cheers

well, why don't you just go there and spew your bafflegab about how
you can prove that they were right to do that!

someone once wrote:

Qrz forum has a new posting that states the USN
changed their antennas on the west coast to those tipped from the
horizontal for superior results. This is 60 years ago before the
advent of antenna computers.

Having been in the navy on both coasts, years ago before the advent of
antenna computers, (alert: reality intrudes here) nothing is vertical
or horizontal aboard a ship.

We had absolutely no antennas that were "tipped from the horizontal" -
whatever that means.

73's
Richard Clark, KB7QHC

On Apr 29, 1:07*pm, JIMMIE wrote:
On Apr 29, 12:30*pm, Michael Coslo wrote:





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 -

When I was an ET in the Air Force I had a TDY assignment attached to a
project with Hughes. They were attempting to *to implement in software
what Tom was doing in wetware. The purpose was to send high speed(at
the time) radar data over HF SSB . The project was a success but the
final implementation was very different from "stereo diversity"
basically because they could not program a computer to do what the
brain can do very easily.

Jimmie- Hide quoted text -

- Show quoted text -

I was in the US Navy from 1962 to 1982 and encountered the venerable
R-390A receiver on many occasions. By design, the -390 was equipped
for diversity if you manipulated some straps on the rear panel.
However, the one time that I tried to use a pair of -390s in diversity
mode the results were less than spectacular. I was on a ship and we
copied an RTTY broadcast that was being keyed on several frequencies,
all subject to QSB. I suspect that the combined audio signal, even
though it sounded better (less apparent QSB), was degraded by
differing path lengths for the two signals, causing timing jitter on
the recovered TTY signal. Whatever the reason, performance was
worse, not better.

"Sal"
(KD6VKW)

Sal, KD6VKW wrote:
"Wharever the reason, performance was worse, not better."

Sal, thank you for your U.S. Navy service.

My experience with diversity was different. At Radio Free Europe we
relayed broadcast programs by HF radio before communications satellites
existed.

We used Hammarlund SP-600 receivers in triple diversity. We found most
other receivers deficient. Our receiving sites were remote ffrom our
transmitting sites to avoid interference. We used UHF for short haul
relay.

For HF triple diversity each of the SP-600s was connected via an
isolation amplifier with a separate rhombic antenna aimed at its
transmitter. Outputs of the three receivers was fed into a Crosby or
Pioneer combiner which elected the best signal and rejected the other
two.

The horizontal rhombics each required four towers because they were
laterally spaced about ten wavelengths apart for space diversity at one
of the lower allocated frequencies. We, at times resorted to frequency
diversity too.

The receiver operator listened to both of the sidebands of each
transmitted frequemncy and selected the better of the two for reception
manually.

By selecting the cleanest frequencies and sidebands and using the output
combiners to select the instantaneously best of three signals, broadcast
quality programs usually prevailed.

Best regards, Richard Harrison, KB5WZI