[Amps] Article about RMS Power????

[Jim Thomson]

Date: Mon, 20 Jan 2020 18:39:20 -0500
From: "Paul Christensen" <w9ac at arrl.net>
To: <amps at contesting.com>
Subject: Re: [Amps] Article about RMS Power????


<In 1974, the FTC regulated the use of power claims in audio amplifier
<advertising.  They required continuous sine wave testing if it was used in
<an ad.  For a while, audio amplifiers were described in terms of continuous
<power,  but as time went on, I noticed some manufactures were testing the
<FTC's authority by re-invoking the "RMS Power" term.  

##  FTC  sez  to  use  ..continuous  RMS  power,  both  channels  driven  simultaneously  with a test  tone...like  1  khz...
IE,  100%  duty  cycle...  for an  hr...into a  NI DL.    

##  For  a laff....  look  at  heathkit  catalogs   from  1968-1973..  plus  other   advertising material  from  hi-fi  mags  of  the day. 

IPP  watts  ...  Int  peak  power  watts..sorta  like  extreme  low  duty  cycle  material.....  like  7.5%  duty  cycle  pulses  from  a pulse  generator.
PP  watts    peak  power  watts
EIA  watts.....  electronic  industries association
IHF  watts.....  institute of  high  fidelity 
RMS  watts....  but only  for a brief  short  test
Continuous RMS  watts....  but  only one  channel   driven  at a time.....  since  the power  supply  was  too  weak. 
Continuous  RMS  watts...  both  channels driven. 
Music  power  watts. 

U  shoulda  heard the  arguments /fights  in  the  library at  High  school  back  then.    How  the  heck  they  got  from  200  watts  IPP.... down  to  just  15  watts  continuous RMS,
both  channels  driven....  is smoke and  mirrors....all  on  the  same  amp.  

There is  at least  2  more  I  missed  from  the  master  list.   No  wonder  the  FTC came  down  hard.  They  were  still  advertising stereo  amps  in  Canada  with...  IPP watts  as  late as 1978....go  figure. 

Even  older,  1970-1974 vintage  ham  books stated  that  peak  watts were double  PEP  watts. 

100  watt  light  bulb   is  120  volts  RMS  +  .834  amps.  Resistance is 143.88  ohms. 
Peak V  is   169.68      Peak  Current  is  1.1792  amps.  Peak  power    =  peak  V    x peak current....=  200  watts peak.

Now  we  have  P-P  watts......and  also ....  instantaneous RMS  watts.
Then  toss  in....   average  reading  Bird  watts.     My  peak  reading  CD  watt  meter  reads  way  too  high on  ssb..vs a scope. 
Then  we  have  the  RF  ammeter.   They  read  low  on  ssb....  and  look  like  sick  puppies.  

That  audio  site  is a poor  site.  Read  some  of  their  other  articles.....way  too  simplistic.

Jim  VE7RF