Cheap Noise Source:  Anyone have a clue? - Page 1
Forum section: electronics / testgear

author: BillyO
author_rank: Super Contributor
timestamp: May 31, 2023, 10:57:23 pm
content: Hi Y'all.Anyone have any clue about or experience with or a link to an article/document/datasheet for this thing?The only things I know about it is, it's supposed to be flat out to 2GHz and it cost $16 CDN. These two things might seem mutually exclusive and probably are.Any information would be helpful.

author: Kim Christensen
author_rank: Super Contributor
timestamp: May 31, 2023, 11:41:53 pm
content: Seen some reviews on Amazon that say it's flat up to 1.5Ghz along with some SA screenshots... But not much other info.

author: DavidAlfa
author_rank: Super Contributor
timestamp: June 01, 2023, 04:08:51 am
content: Make a quick stop at our Quality Control sectionThat old lady only breathes cancer sticks and already has caffeine overdose at 8 in the morning.

author: Fraser
author_rank: Super Contributor
timestamp: June 01, 2023, 08:02:48 am
content: I have very similar versions of this noise source. They are a very basic design utilising a noise junction and MMIC amplification. The performance of the unit is dictated mainly by the MMIC amplifiers so take a look at their frequency response plots. They will not be flat ! “Flat” is a poor term to use anyway. There should be a +/- dBm figure across the stated operating range.That said, my units have proved useful over the years and you can always normalise the noise generator output on an SA if using them in a frequency response test.Professional nose generators are actually quite simple in terms of the circuits used, but there is good reason fir the, being very expensive. They have their output manually calibrated fir the required flat response. The cheap eBay units just rely on the MMIC specs to get a reasonably flat output over a range of frequencies. It is often possible to get a decently flat noise signal if you only use a small frequency range rather than trying to sweep the full 2GHz.These are cheap and useful devices, but you need to carefully test and plot the output noise level over frequency if wishing to use them for anything approaching serious use.If you want to learn about noise sources, the Noisecom web site was always an interesting read.https://noisecom.com/I own several of their 1000 series noise sources and they look relatively simple in PCB design, but they are very carefully designed and manufactured devices.https://noisecom.com/Portals/0/Datasheets/NC1000_Datasheet_Rev719a.pdfFraser

author: Fraser
author_rank: Super Contributor
timestamp: June 01, 2023, 08:14:01 am
content: This thread may be of interest to the OP…https://www.eevblog.com/forum/projects/ever-built-a-working-rf-noise-source/Fraser

author: _Wim_
author_rank: Super Contributor
timestamp: June 01, 2023, 08:43:29 am
content: Here is some more info about a very similar pcb:https://www.eevblog.com/forum/rf-microwave/another-ebay-noise-source/

author: BillyO
author_rank: Super Contributor
timestamp: June 01, 2023, 02:28:51 pm
content: Thanks guys. I'll do some reading.

author: radiolistener
author_rank: Super Contributor
timestamp: June 01, 2023, 11:28:03 pm
content: I have exactly this noise source module, here is my measurements for it:https://www.eevblog.com/forum/rf-microwave/another-ebay-noise-source/msg3039194/#msg3039194it also has pretty flat response at low frequency, usable from 100 kHz. There is a little drop down from 50 kHz to 100 kHz and below 50 kHz its noise power drops down rapidly. See picture taken through 3 dB attenuator and 30 MHz LPF.