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Please recommend some vintage models
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Old 23rd September 2020, 01:26 AM   #1
paba is offline paba  Canada
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Default Please recommend some vintage models

Hi all

Iím looking for suggestions for spectrum analyzer that has the following
- high Z input ( but i guess i can get active probe)
- only need up to 11 or 12 Mhz
- tracking generator in box or support for external one is a must.
- 1 measured channel , 2 channels nice to have but not required
- vintage unit to keep my budget low unless modern USB units can do this
- Must measure THD, markers and 3db points
- would need to store one scan and compare with a second like A/B Or display both simultaneously for visual matching and measuring
- export via gpib to print or save or maybe some software out there (usb if modern unit)
- support to display on a larger external screen would be nice like vga out for example or other means

This is for hobby work not a business so canít cost too much <500 hopefully thatís possible.

Myself i only know hp 3585a that meets the need and still over my budget so looking for others.

Thanks
Paba
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Old 23rd September 2020, 02:09 AM   #2
1audio is offline 1audio  United States
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Please recommend some vintage models
it all depends on the dynamic range you need. With a limited dynamic range you can get there with a Picoscope. I had an older ADC 200 that could do all of that. I still have 2 I don't use. That generation used a bidirectional parallel port but worked remarkably well. There is a Picoscope 3204A on eBay for $300 that can do a decent spectrum analysis. probably other digital USB scopes as well. My Siglent can do it but the display is not too useful.

I would caution against older spectrum analyzers since they tend to be big heavy and delicate.

I have 2 Tek 7L5's which are excellent but you need a mainframe etc. which can get out of hand fast.

If what you want is a network analyzer that's different and more challenging. There is this: NanoVNA | Very tiny handheld Vector Network Analyzer Those are cheap, with limitations.
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Old 23rd September 2020, 01:48 PM   #3
CG is offline CG
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Quote:
Originally Posted by paba View Post
Iím looking for suggestions for spectrum analyzer that has the following...
Depending on the dynamic range you need (there that is again...), a Digilent Analog Discovery 2 might do the job for you. Well within your price goal.
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Old 23rd September 2020, 01:58 PM   #4
paba is offline paba  Canada
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Ok thanks
I checked into that and more is always better especially to be better than the DUT but I would say 70db would be fine, more is better but certainly 90bd+ would be overkill.

BTW I just came across the HP 8590L still reading the data sheet to see and not sure what the going price on these is but also looks promising. I'll look at that Discovery unit as well of course.

/Paba
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Old 23rd September 2020, 07:28 PM   #5
thermionic is offline thermionic  United Kingdom
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Quote:
Originally Posted by 1audio View Post
it all depends on the dynamic range you need. With a limited dynamic range you can get there with a Picoscope. I had an older ADC 200 that could do all of that. I still have 2 I don't use. That generation used a bidirectional parallel port but worked remarkably well. There is a Picoscope 3204A on eBay for $300 that can do a decent spectrum analysis. probably other digital USB scopes as well. My Siglent can do it but the display is not too useful.

I would caution against older spectrum analyzers since they tend to be big heavy and delicate.

I have 2 Tek 7L5's which are excellent but you need a mainframe etc. which can get out of hand fast.

If what you want is a network analyzer that's different and more challenging. There is this: NanoVNA | Very tiny handheld Vector Network Analyzer Those are cheap, with limitations.
Out of interest, how low does the 7L5 go in terms of sensitivity? What's the lowest signal it can work usefully with? I don't need one as I have modern FFT analysers, but I have a few working 7000 MFs and have long fancied the 7L5. I've always thought it would be eye candy for the lab, that's not massively useful. But you use it regularly? I could possibly stick it on the O/P of our 2722 which gets used rarely on account of its lack of live FFT.

Thanks
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Old 23rd September 2020, 08:24 PM   #6
1audio is offline 1audio  United States
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Please recommend some vintage models
On screen is 80 dB I think. I don't remember the max sensitivity off hand. I have used it occasionally. Its great for looking at ultrasonic residue from DAC's since it goes to 5 MHz with a 5 Hz bandwidth. I also used it with some other stuff to calibrate an FM modulator and Modulation analyzer. I would just use a soundcard FFT or I used to use a Picoscope on the output of an AP system 1 which worked great. You don't need a lot of dynamic range. You no need a narrow bandwidth to separate real stuff from noise.
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Old 23rd September 2020, 11:50 PM   #7
fredbloggstwo is offline fredbloggstwo  United Kingdom
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Hi Paba,

don't forget that when measuring THD, you can extend the useful dynamic range of a spectrum analyser by using a notch-filter to filter out the fundamental frequency by a known amount.

I seem to remember a dedicated thread discussing this.

Also, using a 'Distortion Magnifier' as designed by Bob Cordell can achieve an extension of dynamic range.

Cheers

Mike
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Old 24th September 2020, 04:21 AM   #8
CG is offline CG
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Great point.

Iím seeing distortion measurements of -150 dBc with a notch filter approach and a QA401. So, I bet you could get well better than -100 dBc with a passive Bridge-T notch filter, one of Victorís test generators, and an Analog Discovery 2.

Analog Discovery 2 THD Measurement
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Old 26th September 2020, 06:36 PM   #9
H713 is offline H713  United States
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How low does it need to go? Few spectrum analyzers go below 9 kHz. Dynamic signal analyzers (DSAs) do, but not all of them go much above 100 kHz.

The Analog Discovery is a ridiculous deal for what it is. Seriously, a 14 bit ADC with 10 MHz bandwidth for something like $250. Bandwidth is a bit limited, and you won't get 10 MHz out of it, however.
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Old 27th September 2020, 02:21 AM   #10
paba is offline paba  Canada
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As much as I wanted a nice heavy HP, ordered on of these.
tinySA | Main / HomePage

Seems despite what the specs say it goes down to 20 kHz and should have no trouble covering the 10.7 MHz I need. A few very encouraging videos on youtube as well.
Lets see in a few weeks when this finally arrives.

Last edited by paba; 27th September 2020 at 02:35 AM.
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