Hi John,
My comments are interspersed below....
> KQ2M--
> >
> > Interesting post, Bob, and generally reflects my experiences
> > with 8/8/8/8 on 10M and 7/7/7/7 on 15M from the early 1990s
> > from Colorado.
> >
> > >Many other times, adding a second or third antenna in phase doesn't
> increase
> > >the signal strength of the guys calling me, but it does "smooth out"
> their
> > >signals so there is less QSB and more "angle coverage".
> >
> > But I have one question (or issue). I believe what you are saying is
> > that the QSB is reduced because of INCREASED angle coverage.
Yes, that is exactly what I was saying. However, I have ALSO noticed what
you were saying, even though it seems quite opposite! I will be more
specific
below....
> > It has been my contention, based on antenna modeling which shows
> > that the higher angle lobes disappear when using a 4-stack and the
> > main lobe is compressed to provide the stack gain,
This is where it gets REALLY interesting!
Modeling at my qth has not always shown that. Or let me put it another way,
when I was modeling my antennas and terrain and the optimum heights to use,
my modeling technique was to specifically graph and print out the OPTIMUM
angles that I wanted and match that up with Dean Straw's data on percentage
of time arrival angles. I would then INDIVIDUALLY model the antenna/height
combo for THAT SPECIFIC angle and use that height. Then I would perform
the same function again and again until I was satisfied that if I were using
each of the antennas individually, that one of them would always have the
absolute best
signal strength at that angle. Then I remodeled the same antennas again and
again
in pairs at different heights for different wave angles to different areas
of
the world until I was satisfied that I had found the magic combos of
heights for all
beam headings from my qth.
In my non-engineering, non-technical method, I was treating my antennas as
though they were single mono banders and then pairs of monobanders so that
in
theory I should always have a single antenna that would be better than the
stack to
almost all areas of the world at all times. Since I usually split my
antennas to
work in different directions (usually 90 degres off from Europe), this
approach seemed to make
the most sense.
The when I would model the three stack or four stack, the modeling patterns
would show many small individual lobes that were fairly narrow rather than a
broad
lobe.
I can't tell you whether my approach made engineering or electrical sense or
not, but my approach seems to have worked incredibly well since I have had
amazing results on 10 and 15 and the patters are SHARP and I constantly have
to
change antenna combos. Everything seems to perform as modeled based on my
initial premise.
Keep in mind that my terrain is extremely variable from the first 10' out to
several miles with lots of hills, depressions, flats and a large dropoff in
most
directions. I am sure that made the lobes much smaller and sharper.
Perhaps you can comment on this - you are far more knowlegeable than I in
this area..
> AND based on
> > a lot of experimenting, that the reduction is NOT due to any INCREASE
> > in angle coverage--but just the opposite. That QSB is due to multipath
> > --multiple signals arriving at different angles and having
differentially
> > varying phases--causing QSB. By virtue of the STACK you greatly
> > reduce the amplitude of the higher angle signals so that there is little
> > out-of-phase signal to cause QSB.
I understand what you are saying, and this may very well be happening.
However,on balance, I have seen LESS qsb and more "coverage" into Europe
with LESS
variable signal strength to that wide area. I believe that is because of the
way I
modeled my antennas and the sharpness of my lobes.
Here is a typical example....
1300z on 15 CQWWCW Small pileup of EU with A UA9, UA3, SP, I, DL and G.
Switching between single antennas, I can hear the UA9 about S7 with the UA3
S9 and the SP S7 and the DL S6 OR I can choose an antenna that will hear the
UA9 about S5-6, the UA3 S5, the SP S9 and the DL S9+.
OR, I can choose the best combo of phased antennas with the UA9 S6-7 and the
UA3, SP and the DL all about the same strength.
This is typical from my location. I don't think the broader signal strength
is because of forced suppression
of certain wave angles.
> I did some testing with a UA9 a decade or more ago with a single
> > 8L antenna as well as a separate 4-stack. While the 4-stack was
> > somewhat stronger, the single Yagi was well over S9. On the single
> > Yagi the UA9 was IMPOSSIBLE to copy due to that "polar distortion"
> > that was due to multiple arrival angles. But on the stack there was
> > NO SIGN of the distortion. Conditions were good enough so that we
> > could work both LP and SP and this removal of distortion was also
> > confirmed on the LP.
> >
> > I believe the QSB is due (in many cases) to a couple of angles of
> > arrival that are slowly varying in phase over time. And that the
> > polar distortion is also multi-path but with two or more paths that
> > are varying in phase very rapidly.
UA9's and deep polar path q's are a TOTALLY different ballgame! :-)
Yes, suppression of the multiple arrival angles is essential to working
these guys under those conditions! I can't tell you how many times I would
listen to a
LOUD UA? on 40 meters on CW in the morning, and no matter what I tried, I
could
never copy the guy because I do not have a highly directional 40 meter
antenna that I
can rotate.
I certainly agree with you here but I don't think this is what is happening
at my qth with regards to stacking and Europeans. Perhaps if I modeled
everything
differently or my terrain was different, I would be seeing what you were
telling me.
> > In any case, STACKS ROCK! (And I miss them here in south TX--
> > but they will return one of these days.) And I know the stacks worked
> > quite well since I had good EME echoes on both 10M and 15M--perfectly
> > confirming the modeled antenna pattern.
The array of bewildering echoes, different beam headings that are DIFFERENT
based on the difference is height and other weird propagation effects sure
make a 4
stack a really fun antenna to play with. Unfortunately MOST of the fun and
games can be
seen only at the top of the cycle at my qth. I look forward to 2009 when
it will be
lots of fun again!
73
Bob KQ2M
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|