FFT of the Sovereign signal PART 3

[Sean Goddard]

Here's the FFT showing the something(th) harmonic @ 39.3KHz.

Actually the amplitude is fairly even over the entire spectrum, NOT as I posted previously that it tailed off.

Maybe (Hmmm) Minelab have something going on there.

Still, I don't believe they demod ALL the supposed 17 frequencies.

Look CAREFULLY, see those TWO frequencies are prominent? I reckon these are the TWO the Sovereign ACTUALLY uses.

Anyone care to lend me an Explorer to pull to bits to perform the same test on please?

[Carl]

Thanks Sean!

The Explorer waveform is identical, I believe. Just this week I was writing a MathCad spreadsheet for doing an FFT on both the Explorer and DFX waveforms. I also ran a Spice sim/FFT to correlate. I left off trying to figure out how to convert the spectrum to dB and get the range correct, referenced to 0dB. I'll try to finish it up this week and post.

I had also planned to run a hardware FFT on both detectors. However, I don't think we have a spectrum analyzer that goes that low. So instead, what I might try is one of our ADC data acquisition boards, when can then do a software FFT. It can buffer up to 1 million samples.

- Carl

[Dave Johnson]

thanks, Sean. n/t