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