Electronics > RF, Microwave, Ham Radio

Mixer usage in spectrum analyzer


Most analyzers start at 9kHz, which is upconverted to a IF.  The mixer output will be LO+9kHz and LO-9kHZ.   

If The RBW > 18kHZ (which is not so strange) the detector 'sees' both signals, for lower RBW  it might just see 1 of the 2
If it would be an FFT analyzer which f.i. takes an FFT of an  IF bandwidth of 10MHz it will show both signals.

Does anyone know if my assumption is correct and how an SA deals with this behaviour, which mainly applies at the lower end of the spectrum ?


in a nut shell people don't like using spectrum analyzers for audio work so much

David Hess:
The solution I have seen is a warning in the documentation or lockout to prevent a wider RBW than the sweep start.


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