Thanks. Looking at your other plot, I think your spectrum analyser plot is a plot of noise output vs frequency. It looks like your noise source has a steeper noise reduction than mine as the frequency is reduced. It may be that your noise source has a different capacitance value for the dc blocking cap inside it?
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I can try and come up with a better way of measuring mine to try and characterise it better. I didn't spend much time on this last time. I don't think it will reduce by 2dB by 2MHz and by 4dB at 1MHz though.?
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I've also got a couple of homebrew noise sources here. One contains a decent Noisecom noise diode and the other uses a high frequency diode. I think it's a Schottky diode but I can't remember now. It works very well up to several GHz. The Noisecom source is only really good to about 1300MHz although it is supposed to work down to 200kHz according to the datasheet.
