[Elecraft] XG3 device...

[Wes Stewart]

Good questions.  I had them myself, especially #2.

Wes

--- On Thu, 4/14/11, John Ragle <tpcj1r03 at crocker.com> wrote:
>      The more I
> have glanced through the specs for this device, the more 
> puzzled I have become. I grew up on signal generators that
> put out a 
> (good approximation to a) sine wave. This device is
> described as an RF 
> "square wave" generator, which I take to mean that the
> output wave shape 
> is a trapezoid with very fast rise and fall times. As
> everyone knows, 
> the harmonic content of an ideal square wave falls off as
> 1/N. In other 
> words, this device is a harmonic generator, par excellence,
> very rich in 
> harmonic content. To get a sine wave, one has to run it
> through a 
> bandpass filter. In this case, the bandpass filter is the
> receiver to 
> which you connect it.
> 
>      So there are two questions.
> 
> 1. What is the "frequency?" This term usually refers to a
> sinusoid, in 
> which case the answer is trivial. Presumably the
> "frequency" meant here 
> is the fundamental component of the "square" wave, but the
> true answer 
> depends on the shape of the on/off switching, which
> presumably depends 
> on the "frequency" one has dialed into the device. Is one
> getting more 
> or less a 1/N dependence on amplitude at all frequencies?
> 
> 2. When one refers to the calibrated "levels" of output, is
> one 
> referring to the level of the square wave or of its
> fundamental 
> sinusoidal component? Clearly, these are related...but
> which is meant? 
> What about the high frequency end of the operating range,
> where the 
> spectrum may well depart substantially from 1/N (because
> the trapezoid's 
> edges are less "sharp").
> 
> Neither of these questions has anything to do with the
> "phase noise" 
> specification.
> 
> John Ragle -- W1ZI
> ______________________________