- Text file containing derived spectral measurements
- Raw audio WAV file
- HF Radio Receiver with a stable frequency reference
- Computer capable of running Spectrum Lab Software
- Spectrum Lab Software
- Soundcard capable of 11025 Hz sample rate
- Set the radio to USB mode tune it 1 kHz below the signal to be measured. You will hear a roughly 1 kHz tone. The frequency will be affected by the ionosphere, the DDS error in the receiver, and sample rate error.
- Set the radio to AM mode and tune it to the frequency of the signal to be measured. Mix in a local oscillator set to 1 kHz below this frequency. This measured frequency in this method will be affected by the ionosphere, the sample rate error, but not the DDS error in the reciever.
Spectrum Lab Configuration
- Configure Spectrum Lab to sample audio at 11025 Hz.
Figure 2: Spectrum Lab Audio I/O settings.
- Configure Spectrum Lab to compute 512k-point FFTs.
Figure 3: Spectrum Lab FFT settings.
Configure Spectrum Lab to overlap FFTs in time, producing a new FFT every 12 seconds.
Figure 4: Spectrum Lab spectrum settings.
- Configure the processed file output parameters of Spectrum. To do this, go to File --> Export FFT and make your settings match those in Figure 5.
Figure 5: FFT file contents settings.
- Enable saving of the processed data file.
Figure 6: FFT filename settings.
Figure 7: Example FFT file.
- Enable streaming/saving to a WAV audio file:
Figure 8: Enabling streaming/saving to a WAV file.