Good texts on application of White Noise for testing? - Page 1
Forum section: electronics / testgear

author: 6SN7WGTB
author_rank: Regular Contributor
timestamp: March 13, 2023, 08:00:02 pm
content: Can anyone point me towards good texts/books/links/manuals for applying White Noise for audio and RF testing?I'm aware of various uses but cannot seem to find any good compendiums.Thanks

author: jonpaul
author_rank: Super Contributor
timestamp: March 13, 2023, 10:25:39 pm
content: 6SL7See,old,Genrad book, audio noise,measurementwhite,noise,is for,RF, pink noise,is,3db/ Oct rolloff, flqt energy près octave,,1/3 octj

author: pdenisowski
author_rank: Super Contributor
timestamp: March 13, 2023, 10:27:44 pm
content: Noise figure testing with spectrum analyzers (Y-factor method) requires the use of a broadband noise source for the device under test input.https://www.rohde-schwarz.com/us/applications/the-y-factor-technique-for-noise-figure-measurements-application-note_56280-15484.htmlI also have a video on this topic that will be posted to the Rohde & Schwarz YouTube channel in the next week or two.

author: G0HZU
author_rank: Super Contributor
timestamp: March 13, 2023, 11:04:55 pm
content: The 1MA178 paper by R&S is an excellent reference if you want to do your own Y factor measurements because it includes step by step equations and worked examples. HP/Agilent/Keysight provide AN-57 as an alternative. I'd recommend reading both.I've got a lot of experience with noise sources and noise measurements, including NPR testing. The classic old book for NPR stuff was the White Noise Book by M.J. Tant (Marconi). However, this is very dated now and of limited use today. I still have my copy here.For more general testing (with noise) the quality of the noise source is usually quite important. The crest factor, flatness vs frequency and the source VSWR are all important factors that affect the quality of the noise source. I've got quite a few noise sources here, mostly homebrew but all have very good performance. It's worth studying all the contributors to measurement uncertainty and also look at ways to preserve the crest factor of the noise source. An old rule of thumb at work was that the p1dB of any amplifier should be at least 14dB higher than the average power of the noise. It's generally best to aim for 16-18dB. This is important when designing/building a high level and wideband noise source for use as a bench instrument.

author: G0HZU
author_rank: Super Contributor
timestamp: March 13, 2023, 11:19:09 pm
content: Here's the classic old version of AN57-1 and AN57-2 by HP.http://www.hparchive.com/Application_Notes/HP-AN-57-1.pdfhttp://hparchive.com/Application_Notes/HP-AN-57-2.pdfSome hints and tips in the link below for making better noise figure measurements:https://www.ab4oj.com/test/docs/5980-0288E.pdfTo achieve low overall measurement uncertainty when measuring something like an LNA requires really good (and stable) test equipment. One also has to know which noise source and/or measurement method is best to use for a given task. I'm lucky in that I have a pretty good setup here for measuring the noise figure of RF amplifiers up into the GHz region.

author: 6SN7WGTB
author_rank: Regular Contributor
timestamp: March 14, 2023, 07:19:22 am
content: Thank you all - these are really helpful texts - I was finding that general web searching was ending up with audiology mainly.

author: 6SN7WGTB
author_rank: Regular Contributor
timestamp: March 14, 2023, 07:21:35 am
content: Quote from: jonpaul on March 13, 2023, 10:25:39 pmDo you mean the Genrad Noise Generator 1390 and 1381B Operating Manuals?I used the 1390 one to restore my Dawe 419S, for which no data or manuals appear to exist.

author: pdenisowski
author_rank: Super Contributor
timestamp: March 14, 2023, 08:55:08 am
content: Quote from: G0HZU on March 13, 2023, 11:04:55 pmMost modern NPR testing is done using a vector signal generator that can create a notched signal rather than a noise source and a notch filter. I mention this in my video on NPR

author: pdenisowski
author_rank: Super Contributor
timestamp: March 14, 2023, 09:01:24 am
content: Quote from: 6SN7WGTB on March 14, 2023, 07:19:22 amI feel your painOften when I'm researching certain topics (like total harmonic distortion, analog modulation, etc.) I get hits that are mostly AF rather than RF.Noisecom actually also has some nice materials on the use of RF noise sources:https://ps.noisecom.com/ans

author: RoGeorge
author_rank: Super Contributor
timestamp: March 14, 2023, 09:20:50 am
content: Quote from: 6SN7WGTB on March 14, 2023, 07:19:22 amSearch engines are very sensitive to your search and/or browse history. If your browse history happen to include some audio links you visited, then further searching terms, like noise, will return to you results that are mostly about noise in audio. You'll find yourself in some sort of an "online history bubble" that is hard to escape from.You'll have to guide the search engine out of the bubble, for example by adding RF together with the other searched words. Sometimes google scholar might get better results than normal Google.White noise in testing is a rather narrow topic, and for a very specialized usage. I guess not many textbooks, if any, will cover that exact topic alone. Though, noise in general and white noise in particular might be mentioned or constitute a chapter/sub-chapter in many textbooks.

author: jonpaul
author_rank: Super Contributor
timestamp: March 14, 2023, 10:52:42 am
content: Use GenRad/General Radio noise sources 5 hZ...50 kHz GenRad 13811390 Valve gas tube to 5 MHzFor RF sources use microwave noise diodeFor microwaves use gas tube noise source, requires HV ps. eg HPX347ANone are really "white" noise, all vary in noise PSD with freqSee the many fine books on microwave noise measurement.Jon

author: mawyatt
author_rank: Super Contributor
timestamp: March 14, 2023, 03:30:47 pm
content: Quote from: pdenisowski on March 14, 2023, 08:55:08 amBack around 1980 most generators for producing NPR measurements were the noise source & notch filter type (some were heterodyned up/down to fixed crystal filters to produce the notches which allowed the effective notch to move in frequency). We developed basically an AWG with some AD hybrid DACs, massive array of SRAM and an Apple II. Using an IFT we would draw the desired frequency domain, then perform the IFT and load up the SRAM. Recall we could produce NPR waveforms around 60~65dB back then. All this was for development of a battery power handheld Real Time SA based upon the CZT utilizing custom CCDs we developed.Back in 2000 era we were able to see the Keysight developed Griffin DAC chip produce an NPR of better than 75dB, later to become the center-point for their advanced high performance AWGs. We were interesting because of the problem of "Electronic Fratricide" causing one to jam one's own communications, and the solution then was to use an electronic tunable filter for the receiver input. We wanted to use a more DSP centric solution where the jamming waveform would dynamically have the receiver band "notched" out thus requiring a extremely good DAC for the core jamming waveforms production.Best,

author: meteo
author_rank: Contributor
timestamp: July 17, 2023, 12:06:11 pm
content: I am fond of tube audio technology. At the moment I am trying to create a small home measuring bench, for the simplest measurements. Could you help with advice on measuring the frequency response of passive and active components? I understand I need white noise generator and a sound card. For analog devices (tube amps), distortion is about 50-60 dB, for digital audio (rare type DAC) - 80-100 dB. Can you recommend me a white noise source with low amplitude deviation for this kind of measurement? And what should be parameters with a margin? According to my feelings, +/- 0.05-0.1 dB, in the range of 4 Hz - 50 kHz. Or at least 10 Hz - 40 kHz.I bought the Bruel & Kjaer 1405 - white and pink noise gen, but it has the 0.6 dB deviation on White. Too much I think. This device is very old, it may need to replace the electrolytic capacitors and calibrate. I attach the frequency response 1405 - 20Hz_100kHz white noise and amplitude stability. My sound card up to 30 kHz measures. I do not know the lower frequency threshold yet.I looked at the description of the parameters Bruel & Kjaer 1027. "2 Hz - 200 kHz. 1027 an extremely good amplitude stability, of the order of ±0.1dB over an 8 hour period." Is this gen real good?Also, I will need to take acoustic measurements. Pink noise, measuring microphone (4Hz - 30kHz) and audio card. Also, I need a source of pink noise.