Date: Wed, 24 Nov 2010 17:26:28 EST
From: K7LXC@aol.com
Subject: Re: [TowerTalk] STACKED 40 METER BEAMS MATCH
To: towertalk@contesting.com, john@kk9a.com
Message-ID: <11c433.2beaf59e.3a1eeb14@aol.com>
Content-Type: text/plain; charset="US-ASCII"
In a message dated 11/22/2010 6:24:02 P.M. Pacific Standard Time,
towertalk-request@contesting.com writes:
> I installed a StackmatchII+ a week ago on my 40m beams at 160' and 75'
and I tested it out thoroughly during the Sweepstakes contest this weekend.
In
nearly all cases, BIP was better than BOP so I rarely used BOP.
QSL that. If you've ever seen Bob Heil's presentation on in-phase and
out-of-phase, it's no surprise that the Both Out of Phase rarely produces
anything productive.
## out of phase audio is apples and oranges to ant BOP operation. BTW,
if you
use white noise from between 2 x FM broadcast stations, and rvs the wiring
to one speaker, then point the speakers directly towards each other, it will
be dead quiet,they will completely cancel, if aligned correctly, even with
volume cranked up. That was shown to me back in the late 60's...and is a
good demo, nothing new there. Why heil uses 'out of phase' on some of his
headsets is beyond me. That's another old trick from the 60's..supposedly
to enhance weak signals. I never found it to work very well, and a few of
us
had modified headphones with a dpdt miniature toggle on the left ear, just for
doing a phase reversal. What will work, is if one ear is slightly delayed
from the
other [lagging]... IE: a partial phase reversal..just a few degrees, not a
full
blown 180 deg reversal...such that it results in a 1-2 msec max delay.
That's easy to do these days, with dsp audio rack gear.
## The ARRL HFTA program is flawed somewhere. Apparently it uses simple
ray analysis in the far field only. In the old w2pv literature /notes, w2pv
modeled
a 20m yagi at 150'.... and varied the height of the lower yagi from
65/75/85'. The BIP
gain peaks when using the lower yagi at 75'..and drops off at 65/85. HFTA
on the
other hand shows the gain increasing, as the lower yagi keeps getting higher
and higher.
Try it, it's bizarre. Gain is lowest, when lower yagi is say 65'...then
just keeps on increasing, as
you raise it!
When the bottom yagi is a 130', it's still increasing. [top one stays put
at 150']. Since the HFTA
program does not factor in near field interaction/mutual coupling, etc, that
might explain the dismal
results. [ it was w2pv who 1st suggested the BOP mode]. Who knows, maybe
at the top of the
next cycle, [ when angles are usually a little higher], BOP may actually
work...more often.
## the HFTA software, when modeling 2 x 40m yagis, at 161' and 80'......
[and also 180' + 79']
depicts BIP blowing away TOP every time, hands down. It also depicts BOP
as blowing away
BOTTOM every time. The thought after seeing that was... why even mess with
an upper/lower
bip/bop switching set up? BIP/BOP is all that's required. Well BOP
is a dud... 98.92% of the
time. Before the simple BIP /BOP switch was built, the old set up was a
stack match with Top
/bottom/ both.. [ NO bop]. In no case did the lower 40m yagi ever out
perform either the TOP,
or BOTH. We had high expectations for this BOP mode, but after hundreds
of tests, it rarely
improves signals. The bottom by itself, is even worse. BIP reigns supreme
over the TOP, so what's
really required, is just BIP 100% of the time. And the easiest way to
implement that is a simple
L network. [ then u end up with a perfect 50-50 pwr split too].
## OK, now this is just 40m, with yagi's at 180'/79' . I usually see no
short skip on 20-10m, so suspect
the BOP mode would be even worse on the higher bands.
Later... Jim VE7RF
Cheers,
Steve K7LXC
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