This plugin can be used to scan a range of frequencies looking for a transmission and then tune another channel (such as an AM or DSD Demod) to that frequency.
With the Run Mode (11) set to Multiplex, it can also repeatedly cycle through frequencies listening for a fixed period of time. This can be used, for example, to
receive both AIS and ADS-B data via a single SDR.
Note that when scanning, the device centre frequency will often not be set exactly to the frequencies you enter.
The Frequency Scanner will typically try to set the device centre frequency in order to
scan as many frequencies simultanously as possible, and also avoid having a DC offset within the bandwidth of a scanned frequency.
The demodulator channel's frequency offset option will be used so that it receives at the specified frequency.
This setting is typically used to avoid having the channel (1) centered at DC, which can be problematic for some demodulators used with SDRs with a DC spike.
t_rtx: When Run Mode (11) is not Multiplex, specifies the time in seconds that the Frequency Scanner will wait after the power on the active frequency falls below the threshold, before restarting
- Peak: Power is the highest value in all of the bins, averaged over the scan time (6).
- Total: Power is the sum of power in all of the bins, averaged over the scan time (6).
Peak can be used when you wish to set the threshold roughly according to the level displayed in the Main Spectrum.
Total is potentially more useful for wideband signals, that are close to the noise floor.
<h3>11: Run Mode</h3>
Specifies the run mode:
- Single: All frequencies are scanned once. Channel (1) is tuned to the active frequency at the end of the scan. The scan does not repeat.
- Continuous: All frequencies scanned, with channel (1) being tuned to active frequency at the end of the scan. Scan repeats once the power on the active frequency falls below the threshold (4) for longer than the retransmission time (7).
- Scan only: All frequencies are scanned repeatedly. The channel will not be tuned. This mode is just for counting how often frequencies are active, which can be seen in the Active Count column in the frequency table (14).
- Annotation: An annotation (description) for the frequency, that is obtained from the closest matching [annotation marker](../../../sdrgui/gui/spectrummarkers.md) in the Main Spectrum.
- Power (dB): Displays the measured power in decibels from the last scan. The cell will have a green background if the power was above the threshold (4).
- Active Count: Displays the number of scans in which the power for this frequency was above the threshold (4). This allows you to see which frequencies are commonly in use.
- Notes: Available for user-entry of notes/information about this frequency.
- Channel: Specifies the channel that should be tuned when this frequency is active. If blank, the common Channel setting (1) is used.
- Ch Bw (Hz): Specifies the channel bandwidth in Hertz. If blank, the common Channel Bandwidth setting (8) is used.
- TH (dB): Specifies the power threshold in dB that determines whether this frequency is active or not. If blank, the common Threshold setting (4) is used.
- Sq (dB): Specifies a squelch level in dB that will be applied to the Channel when active. If blank, the squelch level will not be changed.
