Examples of Broadband Snapshot Data

1. No wave activity

When no wave acticity is present, the narrowband channels are flat.

For the broadband system, the Automatic Gain Control will be set to its highest level, 48 dB and no features are seen in the snapshot. This plots show a spectrogram (frequency vs. time) for each snapshot.

If instead of creating a spectrogram, we just take the FFT of one of the snapshots, we get the following. No distinguishing features are present. However, the roll off of the anti-aliasing filter can be seen at <1kHz and >3kHz.

2. Chorus

Chorus is a band limited signal that usually appears beetween 500-1500 Hz. It is usually seen for several hours during the day especially between 1200 - 1800 UT and on the narrowband channels will look like this:

Here is a broadband snapshot series for the same day. As can be seen, most of the activity is below 2kHz and the automatic gain control was set to 36dB.

Here is an FFT of the 1605 UT broadband snapshot:

3. Auroral Hiss

Another waveform which we often see is auroral hiss. It is a thermal noise like signal that covers the frequency range of 1-40 kHz. It is usually seen at night from 2000 - 0200 UT.

Unfortunately, in the broadband snapshot it looks like noise across the entire band. However, note that the gain is set to 42 dB.

Due to the Automatic Gain control, an FFT of Auroral Hiss looks the same as when no wave activity is present since hiss covers the entire band.

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