On eBay, chinese sellers are offering what they call a “SMA noise source/Simple spectrum external tracking source DV 12V/0.3A”. I bought one to test it and here are the first results...
CNG 90 STC
CNG 70 USB
- The noise source does not provide a very constant signal level across the frequency range, since the variations are of +/-10dBuV
- There are constant spikes of +/- 5dBuV
- Still, for less than 20 Euro you can perfectly use it to test filters or problems within the distribution network.
- You need a spectrum analyser do make any use of the noise generator
- I would not recommend it for calibration purposes (as advertised on eBay for the “USB 138M-4.4G SMA signal source, signal generator, simple spectrum analyser 1kHz”, which I have not tested, yet)
- The spectrum analyser should have a functionality that allows superimposing a stored spectrum image to the current spectrum image, in order to easily see what is happening in the distribution network or after inserting a filter. Most professional spectrum analysers offer such functionality