Re: XG3 device...
Posted by
Scott Ellington on
Apr 14, 2011; 7:53pm
URL: http://elecraft.85.s1.nabble.com/XG3-device-tp6271930p6274183.html
It's implicit in Alan's posting, but note that symmetrical square waves have only odd harmonics. The even harmonics will be very, very weak, present at all only because the square wave isn't quite perfectly symmetric.
Scott K9MA
Scott Ellington
Madison, Wisconsin
USA
On Apr 14, 2011, at 1:26 PM, Alan Bloom wrote:
> Question 1: The frequency is based on the period of the square wave, in
> other words, the frequency of the fundamental. If you program a
> frequency greater than the maximum 200 MHz, software automatically
> selects the proper fundamental so that the harmonic comes out at the
> desired frequency.
>
> Question 2: I wasn't one of the XG3 designers, but my understanding is
> that the amplitude is that of the fundamental (the sine-wave portion)
> and does not include the harmonics. When you are operating on a
> harmonic, the amplitude is uncalibrated. Although theoretically the
> third harmonic is 1/3 the amplitude (-9.5 dB) and the fifth is 1/5 the
> amplitude (-14 dB) it is not very accurate because of the finite
> rise/fall times of the square wave.
>
> For most things you use a signal generator for, the harmonics don't hurt
> anything - they are filtered out by the receiver or other device under
> test. Even expensive professional signal generators typically only
> specify 30 or 40 dB harmonic suppression.
>
> Alan N1AL
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