[Elecraft] XG3 device...

[John Ragle]

     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