A square wave's frequency is the frequency of the fundamental component. In the XG3 that's 1.5 to 200 MHz. As the manual states, the output levels are calibrated for the fundamental frequency range - 1.5 to 200 MHz.
As you know, a "square wave" is, mathematically, simply a sine wave and infinite harmonics of that sine wave, all added together. Since infinity works better on paper than on the work bench, all "real-world" square waves are a little less than square and the amplitude of the output diminishes at the higher harmonics. Ron AC7AC -----Original Message----- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of John Ragle Sent: Thursday, April 14, 2011 1:15 AM To: elecraft@mailman.qth.net Subject: [Elecraft] XG3 device... 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 ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
