[AMRadio] Re: Looking for Linear Amp

Fri Dec 19 12:56:46 EST 2003

In a message dated 12/19/03 4:44:36 AM, w5omr at w5omr.shacknet.nu writes:

> I spewed my drink all over the monitor when on Friday 19 December 2003 
> 01:41, 
> W7QHO at aol.com said (and I am -not- making this up!)::
> 
> > In a message dated 12/18/03 10:41:35 PM, eccm at swbell.net writes:
> > > It has been my experience that of everything is workig right, and the
> > > output circuit is efficiently designed, the maximum reliable power
> > > output from a linear amp running standard AM is about equal to half
> > > the total rated plate dissipation of the tube(s). i.e. for a pair of
> > > 6146's, 20-25W carrir, 80-100W PEP.
> >
> > Good rule of thumb.   I've operated my home brew 3-1000Z linear on legal
> > max AM.   The tube is dissapating about 800 watts under carrier only condx
> > in this mode and the plate runs a nice bright yellow-orange!
> >
>  Dennis. what are you calling "legal max AM"?
> 
> The only legalities we have anymore, is 1500w PEP output.
> 
> Depending on the natural asymetricalness of your voice, will depend on how 
> much PEP output you have (which is quite difficult, at best, to measure).
> 
> The Rule of thumb is, if you modulate a carrier to 100% with a sinewave, the 
> 
> Peak Envelope Power Output is 1,500 watts.  That would the carrier 
> power(x4). 
> or 375w of carrier output, or (roughly) 500w DC input to the final.
> 
> The problem with that is, we don't speak in sine-waves ;-)
> 
> For more information on figuring PEP power, see 
> http://www.qsl.net/wa5bxo/amplitude-modulation-and pep.htm
> 
> For a great write up on asymetrical audio, see 
> http://www.qsl.net/wa5bxo/asyam/aam3.html
> 
> Dig around the website.  Be careful, though - you might learn something ;-)
> 
> 

So?   My voice happens to be virtually symetrical so 375 watts of carrier for 
1500 watts PEP at 100% modulation is close enough for me.   Looks "legal" on 
the scope too.   Also, running a linear which gives about 33% efficiency at 
carrier only results in "about" 1200 watts input, 800 watts of which is being 
dissapated as heat.   Your 500 watts would be for a class C PA and is about what 
my T368s run   and "I'm not making this up."

Dennis D.   W7QHO
Glendale, CA

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