Date: Mon, 20 Jan 2020 18:39:20 -0500
From: "Paul Christensen" <w9ac@arrl.net>
To: <amps@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
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