Spectrum analyzer question

[rcolarco]

I am going to demonstrate communications signals to a college class using the Analog Discovery 2. I will be generating the signals using a low-power ham transceiver.

What is the frequency range of the signals that will display on the Analog Discovery 2 spectrum analyzer?

Thanks in advance.

[jpeyron]

Hi @rcolarco,

I moved your thread to a section where more Analog Discovery 2 experienced forum members look.

cheers,

Jon

[attila]

Hi @rcolarco

In Spectrum Analyzer you can select a preset frequency range option or have it auto mode, which based on the maximum frequency setting adjust the top frequency.
The resolution is the sampling rate divided by the number of samples. Selecting the 2nd device configuration in WaveForms/Settings/Device Manager doubles the number of samples increasing the resolution.
The minimum frequency depends on the resolution and the bandwidth of the applied window function.

For lower sample rates (<1-2MHz) you could also use the Scope Recording mode to acquire more data and use the FFT or Spectrogram view.

You can find information about the scope input bandwidth in the reference manual:
https://reference.digilentinc.com/reference/instrumentation/analog-discovery-2/reference-manual#scope_spectral_characteristics

 

 

[rcolarco]

Thanks, attila. Maybe I should have been more specific in my question.

What is the lowest frequency input signal the spectrum analyzer will display?

What is the highest frequency input signal the spectrum analyzer will display?

I want to demonstrate AM, FM, and SSB spectra to the students. I will need about 10-20 KHz of bandwidth on the screen to do this. I am restricted to radiating in the ham bands. My initial guess is to radiate a signal at 3.9 MHz, with various modulations. Will the Analog Discovery 2 display such a signal?

 

Thank you.

[attila]

Hi @rcolarco

Having the frequency range in auto mode you can set top frequency to 1Hz, which will result 122uHz resolution, ~1mHz BW. This requires more than 2 hour acquisition.

For maximum 50MHz top can be selected, half of the 100MHz ADC rate. This with 16k sample device buffer results 6kHz resolution, 25kHz BW.

Audio FM looks like this:

[rcolarco]

Thanks, that is exactly what I was after.