Military Signal Intelligence (SIGINT) systems are designed to detect enemy radio transmissions. The interception of such transmissions can provide vital information about the type and location of enemy transmitters and their characteristics.
This "Mini SIGINT" plug-in is designed for surveillance counter-measures (detection of "bugs"). It is basically a spectrum analyzer tailored to the application of searching for unknown, suspect signals. The plug-in controls the receiver and displays a spectrum graph similar to the standard Spectrum Scope, with the added functionality of making it possible to spot and investigate spectra differences quickly and easily.
The displayed graph shows the current band scan and the differences between maximum and minimum values measured over the entire surveillance session. If a signal level difference is greater than a user-defined value, and if the signal itself is greater than a user-defined threshold, then such "suspect signal" region will be highlighted in the graph, indicating a possible presence of a transmitter.
The plug-in is able to save such highlighted areas (suspect signals), either as a text report or a graphical image. If a text report is chosen, this will contain a list of suspect frequencies, associated signal strength levels and the times/dates of intercept.
Before each new session, the user needs to specify the scanning parameters, i.e. the frequency range and the step size; and the parameters related to suspect signal detection, i.e. minimum difference ("Min. Diff.") and minimum level ("Min. Level").
If the minimum difference value is chosen too high, important signals may be overlooked. If it is too low, then even small fluctuations of the background situation on the scanned band may look like suspect signals.
Furthermore, the higher the "Min. Level" value, the stronger the signal needs to be to become "suspect".
It is best to determine both of these values by trial and error, depending on the actual situation on the investigated band.
Note that the selection of the step size determines automatic selection of the resolution bandwidth, which is approximately 17 kHz for step sizes between 12.5 and 25 kHz, and approximately 230 kHz for step sizes of 200 or 250 kHz.
Start Scan - Starts scanning and creates the spectrum display graph.
Stop Scan - Stops scanning.
Zoom In Graph - Zooms in the graph to see more details.
Zoom Out Graph - Inverse of Zoom In.
Move to Previous Suspect Signal - If any suspect signals have been found during scanning, this moves the suspect signal selection back to the previous signal.
Move to Next Suspect Signal - If any suspect signals have been found during scanning, this moves suspect signal selection to the next such signal.
Save Suspect Signals as a Text Report - Creates a report of suspect frequencies found together with the signal strengths and times/dates of intercept in a text form (TXT file).
Save Suspect Signals as Image - Saves a bitmap image of the graph (BMP file).
Options - Makes it possible to customize the plug-in to suit individual preferences. Default colors can be changed under the Colors tab, scanning-related features can be defined under the Misc tab as follows:
Continue scanning if no suspect signal - the receiver will continue scanning until interrupted by the user or if a suspect signal is found;
Mute while scanning - the receiver will be muted while scanning;
Automatic scrolling - the graph will scroll horizontally to reflect the scanning progress;
Restore receiver settings after scan - the plug-in will restore the frequency and mode to which was the receiver was tuned before scanning was started;
Tolerate timing fluctuations - the plug-in will try to eliminate false alarms caused by timing fluctuations between scans. For example, if the rising edge of a signal peak comes a little earlier than in the previous scan, and the difference between the minimum value and the current value is greater than the specified minimum difference threshold, this would normally be seen as a suspect signal.
This is a must have plug-in for surveillance and technical counter-measures applications.