Random source

[KC2UGV]

White, pink, or brown? http://simplynoise.com/

I would think white noise would be the thing (Since it's power is equally distributed over the spectrum), but I need a constant source.

OK, you have to tell me what you're using.
:)

SAQ VLF Receiver + Sound card + Antenna connected to the mic-in port. The software's download link is busted, you you can use SpectrumLab to do the same thing.