[TowerTalk] STACKED 40 METER BEAMS MATCH

[Jim Thomson]

Date: Wed, 24 Nov 2010 17:26:28 EST
From: K7LXC at aol.com
Subject: Re: [TowerTalk] STACKED 40 METER BEAMS MATCH
To: towertalk at contesting.com, john at kk9a.com
Message-ID: <11c433.2beaf59e.3a1eeb14 at 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 at 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