[AMRadio] Side band power with increased carrier/was clipperton on AM

[Gary Schafer]

No, I mean a 2:1 ratio. 
If you have 2 volts above zero and one volt below zero that looks like a 2:1
ratio to me. According to John's "SR" that would be an SR of 3.

73
Gary  K4FMX

> -----Original Message-----
> From: Geoff Edmonson [mailto:w5omr at att.net]
> Sent: Thursday, April 14, 2011 3:15 AM
> To: garyschafer at comcast.net; Discussion of AM Radio in the Amateur
> Service
> Subject: Re: [AMRadio] Side band power with increased carrier/was
> clipperton on AM
> 
> On 04/13/2011 08:01 PM, Gary Schafer wrote:
> > If you read Johns article carefully and reread what I wrote you will
> see
> > that when he uses 660 watts carrier and 1500 watts PEP with his 2:1
> > asymmetrical modulation,
> 
> you mean 3:1 SR, right?
> 
> > that is very close to what I describe using 750
> > watts. Although I used a symmetrical sin wave and found the power in
> each
> > side band to be around 40 watts with 750 watts of carrier and 1500
> watts
> > PEP.
> >
> > If you look at the top of the waveform on John's picture of the
> inverted
> > modulation you will see that the average modulation power is only on
> the
> > very top of the waveform. Also doing the calculations there it would
> also
> > give modulation power of around 40 watts in each side band.
> >
> > With his signal not inverted and running 165 watts carrier in order to
> > accommodate the 2:1
> 
> 3:1
> 
> > wave form, modulation power in each side band and also
> > hit 1500 watts PEP that would also be around 40 watts in each side
> band
> > modulation power.
> >
> > By the way his SR index of 3 is the same as a 2:1 ratio.
> 
> Negative.  The definition of SR *is* the Symmetry Ratio.  In Johns case,
> his asymmetrical audio (and thus the reason for his building up four
> 813's in push-pull parallel) is *3*.   That means, that setting the
> carrier envelope on the scope to consume 2 divisions on the graticule,
> you'll see the positive peaks reach a peak of 6 divisions, and not go
> beyond the base-line negative.
> 
> 6:2 reduces to 3:1
> 
> As an aside, *my* voice is more peaked than John's.    With a Sure 55-S
> microphone, a 31-band equalizer, a modified 100w Bogen audio amp, the
> solid-state Class-B driver, 60Hy of Modulation Reactor with audio
> coupled with 9uF @ 5,000VDC of coupling capacitance, I see on my scope
> an SR of 4.
> 
> My rig is plate modulated, running a pair of 250TH's in the final, and
> another pair of 250TH's in the modulator.  I typically don't run more
> than 150w of carrier, and if I -really- wanted to pour the coals to the
> audio, I'll run double the voltage on the modulators.  That's somewhere
> in the neighborhood of 1500vDC on the final, and 3kV on the modulators.
> Generally, I run 1500v on both, and 0v bias at 1500v on 250TH's in Class
> B draws around 220mA of current.  That's 330w of Power in the modulator,
> -at rest-
> 
> With an SR of 4 (with the B+ high on the modulators) 100w carrier will
> modulate to 1600w PEP.
> 
> Then again, the definition of Peak-Envelope-Power is:
> 
>       Peak envelope power is the /average power/ supplied to the
>       antenna transmission line by a transmitter during one radio
>       frequency cycle at the crest of the modulation envelope,
>       under normal operating conditions.
> 
> 
> >> *Here's the math:
> >> PEP = ((peak-to-peak modulated RF voltage / un-modulated carrier
> >> voltage) squared) * un-modulated carrier power *
> >>
> >> *    This large PEP can occur without negative over modulation, if
> the
> >> modulating audio is acquired by a voice from a microphone. Microphone
> >> audio is generally asymmetrical. *
> >>
> >> *    To help me understand and explain the relationship between audio
> >> and purity of modulation, I've defined a function, which I call
> Symmetry
> >> Ratio (SR). *
> >>
> >> *Symmetry Ratio (SR) defined: *
> >>
> >> *SR = (Peak-to-Peak audio voltage) / (lesser of the two Peak Audio
> >> Voltages above or below the quiescent line)
> >> SR = 2 if the signal is a Pure Sine Wave
> >> SR cannot be less than 2 *
> >> _______________________________________
> >>
> >> This, as a result of John's discovery that his natural voice, as
> viewed
> >> on a scope, is asymmetrical, by an SR of 3.
> >>
> >> Voice patterns are complex waveforms, very dissimilar to a single
> tone.
> >>
> >> An analogy could be drawn from watching the ripples in a pond of
> water,
> >> after a rock is thrown into the center of it.  Further away from the
> >> point of impact, the waves are symmetrical.  However, at the point of
> >> impact, the water is -very- asymmetrical.  Quite disturbed.  Voice
> waves
> >> hitting a microphone diaphragm act the same way.
> >>
> >> The whole explanation, with drawings and diagrams, is available at
> >> http://www.qsl.net/wa5bxo/asyam/aam3.html
> 
> 73 = Best Regards,
> -Geoff/W5OMR