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[TowerTalk] 1dB more RF Power?

To: <towertalk@contesting.com>
Subject: [TowerTalk] 1dB more RF Power?
From: "Jim Thomson" <jim.thom@telus.net>
Date: Tue, 5 May 2020 08:33:27 -0700
List-post: <mailto:towertalk@contesting.com>
Date: Fri, 1 May 2020 00:35:18 -0700
From: Jim Brown <jim@audiosystemsgroup.com>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] 1dB more RF Power?

<Absolutely. When the signal is close to the noise, small differences in 
<the level of the signal become VERY important. And those half and single 
<dB add up. 1 dB from bigger coax or hard line, more/longer radials for a 
<vertical, raise a 40M dipole by 5 ft, or an 80M dipole by 10 ft, or turn 
<an inverted vee into flat dipole at the same height. Three of those 1 dB 
<changes combine for 3 dB (equivalent to doubling the TX power.

####  N6BT  is  adamant that a  rotary dipole  has  6  db  more  gain   vs  an
inverted  vee, with  the  apex of  the  inverted  vee  at  the  same  height
as the dipole.  In  my  experience, an  inverted  vee  is an  omni  directional
ant..and  thats  with a good  CM  choke  used  at the  feedpoint.  A  rotary
dipole  has a 14  db  FS  ratio..and  will  eat an  inverted  vee  for lunch. 



<On SSB, we can increase our loudness on the other end with EQ and 
<amplitude compression. Rolling off everything below 500 Hz adds 3 dB; 
<amplitude compression set for 10 dB on voice peaks adds that 10 dB. That 
<13 dB is equivalent to multiplying TX power by 200!

<73, Jim K9YC

##  Nonsense.  Rolling  off  everything  below  500hz  is  fubar.  It  will
...and  does,  sound  like a  tin  can.   Ditto  with  rolling  everything  off
below  400  hz.   A  gradual  roll off  below  say  350  hz....  followed
by  a pronounced,  steeper  roll off  below  300  hz  works  good.  
As  does a steep  roll off  below 300-325 hz.    But  the  rest  of  the
pass  band  has  to be  very  carefully equalized.  This  is  where
multi  band,  digital   parametric EQ  shines.  Then the  eq  can
be  dialed  up,  dead  on,  and  optimized for  the  application..
...albeit,  a lengthy process.   Then  add  the  compression.
If  you  really  want  to  go  crazy,  multiband  digital  compressors
can  be  used.  End  result  is a helluva  lot  louder..without any 
inband distortion products,  like  what  is heard  when  RF  clipping
is  employed.  Same  concept  as  used by  TV  broadcast.  Commercials
have  6  db  more  average  power  vs  normal  program  material...
with  zero  distortion. 

##  I  looked  at  TV  audio  on  my  spectrum  analyzer,  both  channels
and  full  BW....and  when  the  commercials come  on,  all  the  peaks 
dropped  exactly  .5 db.    Meanwhile the  average  power increased 
by  exactly  6.0  db.   I  could  simultaneously  measure  both  peak  and  
average...   in
.1 db increments.   For  ham  use, the  compression  is  typ increased more
than  6db.

##  since  experimenting  with  ESSB  mode  since  2001,  we  all
noticed  asap,  that  by extending the  top  end  to   3800- 3900  hz,  
phonetics
are no  longer  required..or  used.   Even  with  signals  buried  into  
a  noisy 75m  band,  phonetics  are never  used.   It  gets  even  better
with  top  end  higher  than  4000  hz.   The  drawback  of  course  is
wider bandwidths  are  more  prone  to QRM. 

## We  have  run  hundred of  tests,  and  I  have  several  mini  disc
recordings  of  stations  slowly incrementing  their  top  end in
100  hz  increments,  starting  at 2700  hz....then  2800  hz...etc,
etc,  up  to  3900  hz...and  higher...up  to  aprx 4500  hz.   The 
results  flabbergasts me  every time  I  play that  series of recordings.
The  theory  is...  with top  end  limited to  say  2800  hz....  all  the
consonants  get..crushed.  And  this  is  with  signals  at  or just  above 
the  noise  level.  The  improvement in  intelligibility  is  astounding.
This  is  all  old  news,  since  collins  engineers already  went through this
in  extreme  detail,  as depicted in  SSB  systems +  circuits.

Jim  VE7RF 




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