RF Explorer Pro Audio Edition User Manual
page 12
ANALYZER SCREEN IN ADVANCED MODE
Alternatively, there is a simpler way to increase and decrease frequency span while keeping the center frequency. As this is
a common workflow, the RF Explorer Spectrum Analyzer screen enables the [Return] key to switch between standard
visualization mode and advanced mode.
In this screen above, the frequency reading at the bottom changed from Start/Center/Stop frequency to Span/Center/RBW.
When this mode is enabled, a key press on [Left] or [Right] button will increase or decrease to double and half frequency
span respectively.
As an example, to increase the span from 10MHz to 20MHz, a single click to the [Left] button is enough, no need to go back
to the Frequency Menu.
ADVANCED: UNDERSTANDING RBW
The advanced mode displays the currently selected RBW (Resolution Band Width). This is an important concept for
advanced users.
The RBW references the internal filter used to discriminate the bandwidth of each sweep step. In RF Explorer, each
measurement dot represents a range of frequencies, and there are exactly 112 steps on each sweep. As an example, in a
10MHz span, each of the 112 measurement steps represents 10MHz/112=0.089MHz or, in other words, 89KHz
2
.
The range of frequencies represented on each sweep step is a level of uncertainty; screen resolution is limited to that RBW.
With a resolution of 89KHz on screen (for a 10MHz span), the best accuracy expected is exactly that value. In other words, a
frequency reading of 430.100MHz on screen may mean a range of +-44.5KHz each side, as the filter will not discriminate
further than that for a 10MHz span.
In addition to that, RBW has an important impact on the sensitivity of the Spectrum Analyzer. The wider the filter
bandwidth, the higher the spectral noise and therefore the lower the sensitivity. This is visible by an increasing noise floor
as the RBW is larger, and lower noise floor as the RBW is narrower. Based on this, the narrowest RBW would look like the
better choice for all measurements but as you get a narrower RBW you also decrease the scan speed notably, due to the
slower nature of a narrow filter as well as the need to measure more sweep points to cover the full span.
2
Note the actual value used by the device may differ from the value calculated, due to finite tabulated choices.
