Products > Test Equipment

Good texts on application of White Noise for testing?

<< < (3/3)

jonpaul:
Use GenRad/General Radio noise  sources 5 hZ...50 kHz  GenRad 1381

1390 Valve gas tube to 5 MHz

For RF sources use microwave noise diode

For microwaves use gas tube noise source, requires HV ps. eg HPX347A

None are really "white" noise, all vary in noise PSD with freq


See the many fine books on microwave noise measurement.


Jon

mawyatt:

--- Quote from: pdenisowski on March 14, 2023, 08:55:08 am ---
--- Quote from: G0HZU on March 13, 2023, 11:04:55 pm ---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.

--- End quote ---

Most 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



--- End quote ---

Back 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,

meteo:
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.



Navigation

[0] Message Index

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod