Spectrum Analyzer Measurement Guide : Spectrum Analyzer : BW (Bandwidth) Menu
 
BW (Bandwidth) Menu
Key Sequence: BW
SPA Bandwidth Menu
RBW
The current resolution bandwidth value is displayed in this submenu key. The key displays the Zero Span RBW if Zero Span is selected. The RBW can be changed using the keypad, the arrow keys, or the rotary knob. Bandwidth values increment in a 1 to 3 sequence, from 1 Hz to 3 Hz to 10 Hz, or from 10 Hz to 30 Hz to 100 Hz, for example. Refer to your instrument Technical Data Sheet for the resolution bandwidth range.
Auto RBW On/Off
When Auto RBW is On, the instrument selects the resolution bandwidth based on the current span width. The ratio of span width to RBW can be specified using the Span/RBW submenu key.
VBW
The current video bandwidth value is displayed in this submenu key. The key displays the Zero Span VBW if Zero Span is selected. The VBW can be changed using the keypad, the arrow keys, or the rotary knob. Bandwidth values increment in a 1 to 3 sequence, from 1 Hz to 3 Hz to 10 Hz, or from 10 Hz to 30 Hz to 100 Hz, for example. Refer to your instrument Technical Data Sheet for the video bandwidth range.
Auto VBW On/Off
When Auto VBW is On, the instrument selects the video bandwidth based on the resolution bandwidth. The ratio of video bandwidth to resolution bandwidth can be set using the RBW/VBW submenu key.
VBW/Average Type
Toggles between Linear averaging (arithmetic mean) and Logarithmic averaging (geometric mean). When VBW linear averaging is used, the result is calculated by Linear running average, then Log, and then displayed. When VBW log averaging is used, the result is obtained by taking Log, then running average, and then displayed. These two approaches can result in different responses to time-varying signals.
RBW/VBW
This submenu key displays the ratio between resolution bandwidth and video bandwidth. To change the ratio, press this submenu key and use the keypad, the arrow keys, or the rotary knob to select a new ratio. The default ratio is 3. When the quasi‑peak detector is selected the RBW/VBW ratio is changed to 1.
Span/RBW:
This submenu key displays the ratio between the span width and the resolution bandwidth. The default value is 100, meaning that the span width is approximately 100 times the resolution bandwidth. The value is approximate because resolution bandwidth filters come in discrete steps while span width can be set to any value up to the maximum span of the instrument. To change the ratio, press this submenu key and use the keypad, the arrow keys, or the rotary knob to select a new ratio.