This mode displays the RF signal strength that is detected at specific frequencies defined by the user. The user is alerted when the RF energy detected at one of those frequencies exceeds a threshold (here called the Alert Threshold). Up to 160 frequencies (within the frequency range supported by your analyzer) can be specified and monitored at one time. If the signal strength of an interfering transmitter were to rise above the Alert Threshold (specified by the user) then the corresponding bar for that frequency turns red (otherwise it appears green).
The purpose of this feature is to alert you in the event the ambient RF energy, measured at specific frequencies, were to rise above a threshold value — thereby posing a risk to using a specific frequency as one of the channels you assign to an audio transmitter. For example, in the setting of a live performance where it is important to monitor the channels that have been assigned to wireless audio devices, this feature can be used to ensure those channels are not being impacted by other sources of RF transmissions. Alternatively, if there are wireless devices that transmit at specific frequencies and you wish to monitor their transmissions, then this mode can be used to verify they are currently operating.
The frequencies being monitored are displayed across the horizontal axes according to their ID numbers (as opposed to their frequency in Hertz, as in the Spectrum Analysis views). For example, the green bar above the number 124 in the above screen capture represents the RF energy transmitted at whatever frequency the user defined the 124th monitored frequency as, and this frequency may be either higher or lower than the frequency assigned to the ID number 123, depending entirely upon the user’s definition. When the RF signal strength as measured at a particular frequency exceeds the Alert Threshold then its corresponding bar appears red, otherwise it appears green.
To specify frequencies you wish to monitor select Tools > Monitored Frequencies… from the main menu. The Monitored Frequencies dialog box will then appear.
The check boxes in the leftmost column allow you to select which frequencies you’d like to monitor — if a check appears in the check box then that frequency will be monitored — otherwise, if unchecked, then it will be ignored. The second column (from the left) displays the frequency ID displayed in the chart, as mentioned above. The third column displays the user-defined frequency in MHz which corresponds to the ID number preceding it. Finally, the last column displays a description for this frequency or channel. Typically, the description will correspond to the device assigned to this channel.
The Alert Threshold can be adjusted using the slider control at the bottom of the dialog box. If the signal strength at a monitored frequency exceeds the threshold, the bar above the corresponding ID number will turn red (otherwise it appears green).
As a side note, the Monitored Frequencies dialog box can not be accessed while the analyzer is actively scanning. That is, if the analyzer is scanning and you wish to make changes to the monitored frequencies then it is necessary to first press the Stop button.