# Re: Re: Racing Spark Prediction

Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

I too believe they dont modulate, but when you say:

But a beat waveform can also be considered to be a sin wave amplitude modulated by an other sin wave ie sinA+sinB = SinA * sinB

sinA * sin B is AM modulation and hence the trig identity. I'm confused as to why you brought that up. I believe, when the two sin waves "add" there is not the upper and lower side bands that occur when the two sin waves multiply. In the "added" case, there is a beat frequency associated with A-B that goes up (and the period goes down) when the coupling is increased.

So I was trying to explain that you can look at it in one of two ways.
Two seperate frequency components that beat. This is the usual maths way.

or consider it as one frequency that is modulated by the transfer of energy between the primary and secondary.

But not both ways at the same time.

Modulation was never in my thoughts. Im sorry that you interpreted it that way.

Gerry R.

Original poster: <a1accounting@xxxxxxxxxxxxx>

Hi Gerry,
>
> From: "Tesla list" <tesla@xxxxxxxxxx>
> Date: 2006/05/23 Tue AM 11:16:15 EDT
> To: tesla@xxxxxxxxxx
> Subject: Re: Re: Racing Spark Prediction
>
> Original poster: "Gerry  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
>
> Very informative explanation of the two modes.  Are the two
> frequencies just present (sinA + sinB)

Yes they are just present. They add and therefor beat.

But a beat waveform can also be considered to be a sin wave amplitude modulated by an other sin wave ie sinA+sinB = SinA * sinB

>or do they modulate
> (sinA*sinB) and produce side bands.

No they do not modulate which is the equivlaent of multiplication. The voltage you measure is the sum, the addition of sinA and sinB.

So I was trying to explain that you can look at it in one of two ways.
Two seperate frequency components that beat. This is the usual maths way.

or consider it as one frequency that is modulated by the transfer of energy between the primary and secondary.

But not both ways at the same time.