Author Topic: Inexpensive >=2GHz scope (ETS ok!)  (Read 3232 times)

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Offline OwO

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Re: Inexpensive >=2GHz scope (ETS ok!)
« Reply #25 on: July 17, 2019, 04:56:50 am »
No, no one here seems to be getting the OP's point, so let me ask you this:

Do you have to be able to see the signal's waveform? If so then a SA absolutely will not do. A SA will NOT tell you the relative phase between the fundamental and the harmonics! This is what ETS scopes are for, and if that is truly the use case then people can stop suggesting a SA based solution!
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Offline joeqsmith

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Re: Inexpensive >=2GHz scope (ETS ok!)
« Reply #26 on: July 17, 2019, 05:00:56 am »
Like this?

https://www.ebay.com/itm/LeCroy-DDA-5005A-XL-4-Channel-Disk-Drive-Analyzer-WaveMaster-8500-Oscilloscope/153444975958?epid=1617668161&hash=item23ba088556:g:6ksAAOSwRW9cq-eh

1.5K would be a very good price for a working one with accessories.    A few people here have been upgrading them with new screens and MBs.  You shouldn't have any problems finding help if you have questions about it. 
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Offline hendorog

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Re: Inexpensive >=2GHz scope (ETS ok!)
« Reply #27 on: July 17, 2019, 08:05:18 am »
It sounds like you don't actually need much bandwidth.
So could you downconvert both signals it to a more sensible frequency using two mixers and some cheap PLL board from ebay.

Then use a basic scope such as the Siglent 1000XE series to monitor the phase relationship. It will be the same at baseband as it is at 915MHz.
And it has an excellent FFT which you can make use of for the distortion monitoring.

Get your funding that way and then buy the real deal gear.

There are other ways to do it which are cheaper, but it sounds like you need something which produces pretty pictures as well as being able to be explained.





 

Online Mechatrommer

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Re: Inexpensive >=2GHz scope (ETS ok!)
« Reply #28 on: July 17, 2019, 08:11:13 am »
I'll say this much. There is no modulation and there are specific laws of physics reasons that we are interested in a 915MHz ISM band. This isn't a communication signal, it's not a carrier. I get that everyone wants to tear me apart considering what I've asked, but you're actually assuming a lot that isn't accurate. This is not a typical use case.
Spectrum Analyzer would be nice, but we can't afford both and it's critical to see phase relationship between a signal compared to a master clock/trigger (there is some intentional delay that must be controlled). The distortion/artifacts/reflections are going to be a fact of life and we'll have to do the best we can with a scope to analyze those because for the interim we can't buy both. Hence the scope needing enough bandwidth to hit the second harmonic bare minimum, preferably the third.
from the sound of it, you want something greater than 915MHz fundamental, something 10X BW than  that to see analog nature qualitatively of the signal, and 10X the sampling rate to see some phase difference between 2 signals, and even that, some type of "physics" will not accept that minimum limit (only 1/10X jitter tolerance compared to a period of the fundamental). at your budget and spec, i think you are looking at 20GSps because thats what still available cheap in used market, above that the price immediately sky rocket. maybe Lecroy 3 - 6GHz Wave Master / Pro / SDA / DDA series may suits you at currently affordable budget (200GSps ETS). or maybe are you talking about 91MHz? and want to see the quality of it? with 1-2GHz, all you see is 915MHz sine wave with differing amplitude and jitter spec / phase difference limit dictated by the sampling rate or ETS. ymmv.
Nature: Evolution and the Illusion of Randomness (Stephen L. Talbott): Its now indisputable that... organisms “expertise” contextualizes its genome, and its nonsense to say that these powers are under the control of the genome being contextualized - Barbara McClintock
 

Offline timbojames

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Re: Inexpensive >=2GHz scope (ETS ok!)
« Reply #29 on: July 17, 2019, 09:05:01 am »
Like this?

https://www.ebay.com/itm/LeCroy-DDA-5005A-XL-4-Channel-Disk-Drive-Analyzer-WaveMaster-8500-Oscilloscope/153444975958?epid=1617668161&hash=item23ba088556:g:6ksAAOSwRW9cq-eh

1.5K would be a very good price for a working one with accessories.    A few people here have been upgrading them with new screens and MBs.  You shouldn't have any problems finding help if you have questions about it.

That is what I was eyeballing. Connectors seem to be an annoyance but I've already seen people circumvent the $300 adapters.
 

Offline timbojames

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Re: Inexpensive >=2GHz scope (ETS ok!)
« Reply #30 on: July 17, 2019, 09:14:29 am »
from the sound of it, you want something greater than 915MHz fundamental, something 10X BW than  that to see analog nature qualitatively of the signal, and 10X the sampling rate to see some phase difference between 2 signals, and even that, some type of "physics" will not accept that minimum limit (only 1/10X jitter tolerance compared to a period of the fundamental). at your budget and spec, i think you are looking at 20GSps because thats what still available cheap in used market, above that the price immediately sky rocket. maybe Lecroy 3 - 6GHz Wave Master / Pro / SDA / DDA series may suits you at currently affordable budget (200GSps ETS). or maybe are you talking about 91MHz? and want to see the quality of it? with 1-2GHz, all you see is 915MHz sine wave with differing amplitude and jitter spec / phase difference limit dictated by the sampling rate or ETS. ymmv.

Its two independent tasks. I need to be able to set an accurate delay by looking at phase of a 915MHz pure tone. Second test involves looking at the 'result' (which will have distortion) and to qualitatively get a look at artifacts that I anticipate will be in the second (and possibly third) harmonic range. I know accurately viewing a third harmonic isn't going to happen on a 2GHz scope, I've admitted I fudged that spec. I really need something in 3-4GHz range with suitable sample rates (depending on the sampling scheme used). We at least aren't concerned with accurate phase measurement in that third harmonic range, that's all taking place with the 915MHz unadulterated pure tone. I'm well aware the instrument is going to be a limiting factor, but as you said the price skyrockets to go 10x which is where everyone wants to be.

The LeCroy DDA5005A that we referenced above can do 200GS/s with RIS.

The only thing I meant by 'laws of physics' was someone suggested I do the demonstration at a lower frequency. There's reasons various technologies use the frequencies that they do and what we are pursuing is only practical logistically and physically with a 915MHz ISM band.
« Last Edit: July 17, 2019, 09:26:29 am by timbojames »
 

Online Mechatrommer

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Re: Inexpensive >=2GHz scope (ETS ok!)
« Reply #31 on: July 17, 2019, 09:33:26 am »
if you wait patiently, or get creative you can get used 3-7GHz differential probe for it at around 500 - 700 USD... i collected 3 of these probes during a span of time waiting and stalking and offering at less than 2K. get creative i mean you look separately head and body/adapter that each seller cannot test, so they sell it as is... bargain has becoming more difficult lately but maybe with best offer you can still get at the ballpark price, dont ever expect them to be like rigol probe kind of cheap though, even the active (non differential) ghz probe type.
https://www.ebay.com.my/itm/New-Teledyne-LeCroy-Wavelink-D500PT-6GHz-Differential-Probe-in-cal/323745468566?hash=item4b60bbd096:g:n10AAOSwtfhYnzET

people are working on diy BMA to BNC/SMA adapter at low cost alternative... and/probably later the diy active/diff probes... for agilent brand i'm not sure, they are $1K tag for 1-2GHz diff probe i currently see in ebay.. some agilent or tektronix stalker may give you better advice..
« Last Edit: July 17, 2019, 09:36:05 am by Mechatrommer »
Nature: Evolution and the Illusion of Randomness (Stephen L. Talbott): Its now indisputable that... organisms “expertise” contextualizes its genome, and its nonsense to say that these powers are under the control of the genome being contextualized - Barbara McClintock
 

Offline nctnico

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Re: Inexpensive >=2GHz scope (ETS ok!)
« Reply #32 on: July 17, 2019, 11:16:41 am »
Spectrum Analyzer would be nice, but we can't afford both and it's critical to see phase relationship between a signal compared to a master clock/trigger (there is some intentional delay that must be controlled). The distortion/artifacts/reflections are going to be a fact of life and we'll have to do the best we can with a scope to analyze those because for the interim we can't buy both. Hence the scope needing enough bandwidth to hit the second harmonic bare minimum, preferably the third.

I've been looking at these LeCroy Disk Drive Analyzers because it seems they can be found for about 1.5-2k USD and they have a 5GHz -3db bandwidth and good sampling rates. Reading through the manual, they appear to just be an oscilloscope with some specialty functions for disk drive analysis.
If you want to see the phase relationship then I recommend looking at the Agilent 54835, 54845 or 54846. These have a higher resolution trigger interpolator so you can measure the phase relationship with a higher precision. IIRC the Lecroy scopes in your price range typically have a lowest time/div of 200ps and the Agilent scopes allow 100ps/div.

For looking at distortions spectrum analysis is a better tool. This is available on the oscilloscopes mentioned so far (FFT) but using a spectrum analyser you can get more bandwith and a better frequency resolution for less money.
« Last Edit: July 17, 2019, 11:19:33 am by nctnico »
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline joeqsmith

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Re: Inexpensive >=2GHz scope (ETS ok!)
« Reply #33 on: July 17, 2019, 12:30:54 pm »
It sounds like you don't actually need much bandwidth.
So could you downconvert both signals it to a more sensible frequency using two mixers and some cheap PLL board from ebay.

After seeing that they are not working with a pulse and plan to use the scope's interleaved mode, I was wondering why they wouldn't use a mixer.   Maybe there is something else going on that prevents it.    It sounds like they are trimming the phase and want to measure it.  All derived from the same clock. 
How electrically robust is your meter?? https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg
Software, documentation and test reports for the low cost NanoVNA, V2+4 and LiteVNA may be found here:
https://github.com/joeqsmith
 

Offline Berni

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Re: Inexpensive >=2GHz scope (ETS ok!)
« Reply #34 on: July 17, 2019, 12:55:54 pm »
You can get a 20GHz sampling scope for under a grand if you are lucky enough around the used market, something along the lines of this:
https://www.keysight.com/en/pd-54751A%3Aepsg%3Apro-pn-54751A/20-ghz-dual-channel-electrical-module

But as people have said if you only need it for one special measurement then it might make more sense to rent something like this from an equipment dealer.

 

Offline timbojames

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Re: Inexpensive >=2GHz scope (ETS ok!)
« Reply #35 on: November 08, 2019, 06:14:02 am »
Added a final edit on my original post for the sake of Darwin Sabanovic who was extremely helpful once I got in touch with him. I did get one of his DS800 USB scopes and it has been working great for us for the past couple months. Thanks to everyone else for your advice and guidance as well.
 

Offline ZhuraYuk

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Re: Inexpensive >=2GHz scope (ETS ok!)
« Reply #36 on: November 08, 2019, 01:40:16 pm »

I've been looking at these LeCroy Disk Drive Analyzers because it seems they can be found for about 1.5-2k USD and they have a 5GHz -3db bandwidth and good sampling rates. Reading through the manual, they appear to just be an oscilloscope with some specialty functions for disk drive analysis.

Be aware that those have only 50 Ohm inputs.  I recommend to go for used LeCroy WavePro 7100A. It is fully hacked and bandwidth limit can be unlocked to 3Ghz by removing capacitors and replacing resistors in front end (rest of the hardware is incidental across all 7000 series).  Inputs are 1M/50Ohm switchable in all bandwidth range.
 


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