Both resolution bandwidth (RBW) and video bandwidth (VBW) can be coupled to the frequency span automatically or manually set. When set to Auto RBW, RBW adjusts automatically in proportion to the frequency span. The default ratio of the span width to the resolution bandwidth is 100:1, and can be changed as follows:
When auto-coupling between the span and RBW is selected (the Auto RBW submenu key is toggled to “On”), this is indicated on the left side of the display with the RBW label and underneath it one to three digits followed by the frequency units; this represents the resolution bandwidth value. If manual RBW is selected (the Auto RBW submenu key is toggled “Off”), the label and value turn red and a ‘#’ symbol is shown in front of the RBW label. Adjust resolution bandwidth independently of the span. If an unavailable resolution bandwidth is entered, then the instrument selects the next higher resolution bandwidth. If a value greater than the widest RBW is entered, then the widest RBW will be selected.
VBW can be set two ways – manually or by auto coupling. Auto coupling of the VBW links the video bandwidth to the resolution bandwidth, so that VBW varies in proportion to RBW. Auto coupling is indicated on the left side of the display with the VBW label and underneath it one to three digits and the frequency units; this represents the video bandwidth value. If manual VBW coupling is selected, the label and value turn red and the “#” symbol is shown in front of VBW on the left side of the display. Adjust video bandwidth independently of the RBW. If a non-existent video bandwidth is entered, then the instrument will select the next higher video bandwidth. If a value greater than the widest VBW is entered, then the widest VBW will be selected.
The ratio of the resolution bandwidth to the video bandwidth can be changed by pressing the BW main menu key, the
RBW/VBW submenu key, and then using the keypad, the directional arrows, or the rotary knob to set the ratio. By default, the RBW/VBW ratio is set to 3. The current value of the ratio is shown as part of the submenu key label.
