FFT analyzer recommendations

Hi, all,

I need another FFT analyzer. I really like my HP 35660A, but it only goes up to 100 kHz (50 kHz for two-channel measurements). I'd really like one that goes up to at least 10 MHz, and can do the same sorts of stuff, especially display noise spectral density in different units on different scales and perform frequency response testing easily.

There are a bunch of USB-style things, which might be okay as long as they have Linux software available.

What I really want is a smallish boat anchor with two channels, 14-16 bit resolution, > 50 MS/s sampling, FFT analysis, a nice display, and that can talk to USB sticks.

Any faves?

Thanks

Phil Hobbs

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Dr Philip C D Hobbs 
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Phil Hobbs
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I think you should buy one of the Rigol SA's and report back. Specifically the cheap DSA815-TG.

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George H.

Reply to
George Herold

The Rigols are RF spectrum analyzers, and I already have three of those. I'm looking for a more modern version of the HP 89410A, basically.

Cheers

Phil Hobbs

Reply to
pcdhobbs

Oh are the Rigols OK? I want a SA that goes above 100k Hz too. ~10 MHz would be enough for lots of stuff. Are the Rigols any use in the 1 MHz - 10 MHz range?

George h.

Reply to
George Herold

Entry level SAs are all SDR-based these days, so they make nice pictures and are pretty flexible compared with traditional ones, and in the low-frequency range they're probably fine. I hang on to my 8566es because their close-in phase noise is unbeatable due to their YIG-tuned oscillators and filters, but that really only becomes important above ~100 MHz.

If you're OK with a noise floor around -80 dB from full scale, the Rigol is probably fine, and it's not at all a bad price.

Cheers

Phil Hobbs

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Reply to
Phil Hobbs

Thanks Phil, 80 dB is better than the 50 dB I get with my 'scope FFT.

GH

Reply to
George Herold

Okay, so I put in an eBay 'best offer' on an HP 89441A vector signal analyzer with the two-input option. We'll see!

Cheers

Phil Hobbs

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pcdhobbs

Am 18.02.2018 um 01:44 schrieb snipped-for-privacy@gmail.com:

I have written a program that controls that thing over the network and measures spectra from 0.1 Hz to 1MHz, one FFT per decade, reads the results, combines them and plots them with gnuplot.

One needs a converter box from coax ethernet to contemporary network, then one just opens port 5000-something on 192.168.178.111 and simply reads and writes GPIB-strings. And the coax needs 2 terminations, even when the "cable" is only 5 inch long. :-)

No need for GPIB cards and semi-supported drivers.

These measurements of voltage regulator noise have been done with it: <

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Just in case you win it and are interested.

cheers, Gerhard

Reply to
Gerhard Hoffmann

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Hi, Gerhard,

I did, and I am. I'll have to gin up a nice low-1/f-noise preamp for it, bu t that'll be fun.

Thanks

Phil Hobbs

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Reply to
pcdhobbs

Note that the software options can easily be unlocked on these (although they would be of little use for your intended application).

Reply to
JM

The cell-phone stuff won't help much, but I'm hoping that I can turn on the AYB (spectrogram and waterfall) option without scrooching it. (Option AY8, the internal source, would be useful too, but it's probably a HW option.)

The software one should be no big issue as long as the floppy drive works reliably.

Cheers

Phil Hobbs

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Phil Hobbs

Mine has most options, but I'm not sure about the waterfall. What is missing is the source up converter for the RF section. But for RF I have a real VNA.

That thing has so much parameters to set up that I wrote the program to control it remotely very soon. I had to use a pre-flight check list otherwise.

Important options are dual channel, needed for cross correlation, source for Bode plots etc and memory extension.

My program is in C, under Linux. It probably can be compiled under Windows, too. You'll need a lot of gain to mask the noise in the 1/f region. That eats into the dynamic range.

I'll remove the most embarrassing FIXMEs over the weekend, a good opportunity to clean it up :-)

cheers, Gerhard

Reply to
Gerhard Hoffmann

So my new-to-me HP 89441A analyzer is due to be here Tuesday. I noticed that it doesn't have the serial cable--is it a regular straight-through

9-pin cable, or something weird?

Thanks

Phil Hobbs

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Phil Hobbs

Hi, Gerhard,

Thanks, that would be great. We're an all-Linux shop round here, so no worries there.

Cheers

Phil Hobbs

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Phil Hobbs

Am 21.02.2018 um 02:29 schrieb snipped-for-privacy@gmail.com:

I'm working on a chopper preamp that should be flat down to at least

100mHz, but it seems that I cannot verify that with the 89441A.

It works with parallel ADG819 analog switches, step up transformers, more low noise gain with ADA4898s on 500 KHz, synchronous demodulator back to baseband and some more gain.

A Xilinx Coolrunner II generates the timing from a 100 MHz osc. It looks like I get 120 pV/rtHz.

The main problem is the ringing of the step up transformer. I re-wired some Macom and Pulse SMD transformers under the microscope using 50u wire.

That was no fun. 1/2 :-)

cheers, Gerhard

Reply to
Gerhard Hoffmann

Am 23.02.2018 um 20:15 schrieb Phil Hobbs:

I also had to make the cable myself. It wasn't much work, and it is known how to do it.

Reply to
Gerhard Hoffmann

The DOCs are online, if you don't have them. It appears to be a common serial cable (but who knows how many pins are used). There is also a comment about the EMI suppression ferrite position.

Reply to
krw

I have a 35665A, whose 1/f is pretty good.

At 0.1 Hz? Awesome!

I bet. I once spent about three weeks repairing metal-patterned PVDF pyroelectric films with silver paint for a customer demo, so I feel your pain.

Cheers

Phil Hobbs

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Reply to
Phil Hobbs

You'll be able to do that.

Oh, you got an 89431A as well as a 89410A? You'll soon be welding a couple of 42H racks on top of each other to save on floor space.

Reply to
JM

I got the complete 89441A 2.65 GHz gizmo. I'll move my spare Tek11801C out of the rack to make space. ;)

You can fit a lot in a 7-foot EIA rack.

Cheers

Phil Hobbs

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Phil Hobbs

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