Here's a screenshot of the message I get if I try to reduce the resolution bandwidth below 30kHz while the tracking generator is turned on. Since the message only appears for a relatively short time, and it isn't possible to save the screen with the message directly on USB-Stick, the photo with my cell phone didn't turn out too well. Anyway, it's readable. Yet, I don't understand why there's the lower limit for RBW with the TG open. Rigol's DSA800TG series hasn't got this shortcoming.

Cheers,

Thomas

With TG minimum RBW is 30kHz. (this is also most narrow filter what can not go to FFT mode)

What is problem with it? Do it have too fast response or what?

Here is one small example, Nominal center frequency 21.953MHz, width ~3.5kHz Band Pass filter. (in this example filter under test have problem)

With RBW30 also used Span is 30kHz! (note also used VBW)

With TG there is some DUT between TG output and SA input. This is your "filter" and it have most relevance, not SA RBW filter.

Of course this 30kHz Span is not limit. If narrow filter under test there can use more narrow Span.

As sidenote here is limits with different RBW widths.

Sweep

**Span** limits using FFT or Sweep (SWP) mode

Spectrum analyzer. (TG Off)

10Hz, FFT 33.83MHz, SWP ---

30Hz, FFT 106.6MHz, SWP 330kHz

100Hz, FFT 318MHz, SWP 3.7MHz

300Hz, FFT 793.6MHz, SWP 33,3MHz

1kHz, FFT 2.1GHz, SWP 371MHz

3kHz, FFT, SWP 2.1GHz

10kHz, FFT, SWP 2.1GHz

Spectrum analyzer + TG in use.

30kHz, FFT ---, SWP 2.1GHz

100kHz, FFT ---, SWP 2.1GHz

300kHz, FFT ---, SWP 2.1GHz

1000kHz, FFT ---, SWP 2.1GHz