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Building a phase noise measurement system for digital audio
Building a phase noise measurement system for digital audio
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Old 25th March 2017, 04:07 AM   #21
miklos is offline miklos  Hungary
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Quote:
Originally Posted by 1audio View Post
Simply put I don't know enough about how the noise would show itself. I don't have a phase noise test set. Also it really needs to be tested as a system. The PCB assembly and the casework will all affect the vibration and what happens at the crystal. That's why looking at the analog output seems necessary.
Why not use led as a damping material?
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Old 25th March 2017, 02:44 PM   #22
jborden is offline jborden  United States
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Building a phase noise measurement system for digital audio
Quote:
Originally Posted by gerhard View Post
On my daytime job we have a E5052B and another project member
has a R&S FSUP (?) which gave nearly identical results. I'd like
to keep that capability for myself, at least for some fixed frequencies
like 5, 10, 100 MHz. (being a free lancer)

I use the 49441A currently as an FFT analyzer after preamplifiers of
my own for baseband; I'm still stuck at 190pV/rtHz or so, already too
good after ring mixers, but I'd like to break the 100 pV barrier.... It eats
up lots of time.
I have access to an 89441a and gulp ... thought that BNC connector was an extra RF input of some sort ... should have read the entire manual, I was focussed on replacing a couple caps to get it recovered... as I mentioned, these wonderful pieces of equipment can be had at close to scrap metal prices if one is willing to do a little repair. In any case I'm hitting close to 90% on repairing those PSUs to the point where I *start* by replacing the diodes and caps, and *then* testing...

Quote:
I control the 49441A over the LAN. It took a BNC-LAN to twisted pair
converter for $25, but it works really good. I just open port 5xxx on
192.168.1.111 and feed it GPIB commands and read the results.
I completely ignore its GPIB interface for the finger-thick cable, no
trouble with gpib drivers, AT/PCI-Bus cards and such, had enough of
that 30 years ago.
That's an elegant solution, though my 100mHz pentium with an ISA HP-IB card is part of my technology museum (not entirely original specs as missing the circa 1980s tantalum caps Of course BASIC is a dead end, but I have this warm nostalgic feeling knowing that it is running somewhere, somehow.

I would very much appreciate your C sources.

Quote:
One of the beta testers of my preamp has a working 3048, he uses
it at least for baseband measurements. I could pass him your email
address if you want. Personally, I don't have much interest in restoring
a 3048; some of the people who used to use it ( in my daytime job
environment) said it was really cumbersome, and I value their opinion.

But then if your work is putting satellites into space, the pockets are
much deeper and your perspective quickly adjusts to that.
Fair enough. No doubt more cumbersome than a direct LAN attachment. The 3048a is heavily dependent on software which prompted my original question -- yes I would appreciate assistance or information in that regard.

Quote:
I have a ADC / FPGA / DSP project with 2.4 GHz sampling rate
on the back burner, have done similar things but I must first
flush the pipeline.

I have been killing a few trees around my house with a chain saw today
and put two of them into a container; I'm pretty well done for today.
My back hurts. Not the appropriate job for someone who is used to solder
under the microscope.
Your yard sounds like mine, and I spend most of my day also with a stereo microscope -- but I stand
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Old 26th March 2017, 11:23 PM   #23
gerhard is offline gerhard  Germany
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BTW I was thinking that one 50R-Termination was good enough for 10 cm
of 10 MBit coax network. I was wrong. It took 2 of them, both on the same side
were ok.
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Old 27th March 2017, 12:59 PM   #24
andrea_mori is offline andrea_mori  Italy
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Building a phase noise measurement system for digital audio
What about oscillators metrology with SDR?
https://pdfs.semanticscholar.org/682...3261c904a3.pdf
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Old 27th March 2017, 01:09 PM   #25
gerhard is offline gerhard  Germany
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Take a look at the Timepod, designed by J.Miles (who is on the time nuts list) and now sold by Symmetricom, really now by MicroSemi.
A wonderful thing.
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Old 27th March 2017, 01:24 PM   #26
andrea_mori is offline andrea_mori  Italy
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Building a phase noise measurement system for digital audio
Quote:
Originally Posted by gerhard View Post
Take a look at the Timepod, designed by J.Miles (who is on the time nuts list) and now sold by Symmetricom, really now by MicroSemi.
A wonderful thing.
Just do it, too expensive for an hobbist.
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Old 27th March 2017, 01:55 PM   #27
gerhard is offline gerhard  Germany
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The internals have been published. It is exactly that: a SDR.
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Old 27th March 2017, 01:56 PM   #28
jackinnj is offline jackinnj  United States
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Building a phase noise measurement system for digital audio
There was a fellow giving away the HP-Basic software on the Yahoo user group a few years back -- if you plug in there you might be able to score a copy. If not, pm me.
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Old 27th March 2017, 05:31 PM   #29
jborden is offline jborden  United States
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Building a phase noise measurement system for digital audio
Thanks for the tips on 10base2 ... that was used in the days where I was either working from a VT100 or PC not connected to Ethernet ... or perhaps, just perhaps, the VAXstation was networked that way, never occurred to me to look

Yes the HP-Basic is available, just probably don't have a Series 200 to run on ... but there is also the HTBasic software so a few options.

Moving forward, being able to issue commands over the network is very appealing and probably at some point could get a DOS 486 with a network card and a HPIB card to act as an Ethernet gateway for this old equipment.

The "SDR" approach is very interesting and one of the goals is to verify the measurements against analog. SubHz is where it gets less than trivial -- not that its essential but nonetheless. The FPGA SOCs are getting much more affordable including boards designed for SDR specifically.
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Old 29th March 2017, 05:34 AM   #30
miklos is offline miklos  Hungary
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Rutgers DC receiver would be to complicated to build it for multiple frequency's, needed in digital audio. Looking how he realizing the reference oscillator, damping and things.
Maybe a cheap way could be to use an old color TV color PLL section, I think some dedicated IC's out there which do that job. Also one could investigate the possibility to use a shortwave receiver ,which would receive the DUT oscillator and use a good quality crystal oscillator for the shortwave radio's BFO, than analyze the audio output. Radio's are usually good to 30MHz, to cover the usual CDP oscillators. In reality 1Audio is right, the main thing in digital audio is the audio output of the DAC , and to see there the Jitter one doesn't need to analyze the oscillator, it's enough to look at the audio, for that we have the Wakibaki's copy of the Jitter test signal here on Diyaudio. It's no good for numerical measurements, but good for comparison of different DAC's and the crystals used in the conversion.
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