Re: User Experience of Sampling Scopes
On Sat, Jan 30, 2021 at 07:07 PM, Jeff Dutky wrote:
I'm curious what sorts of things you use the sampling scope to do
You can't appreciate them, unless you appreciate the math. I think they were first used in pulsed RADAR ... but the 500 series based samplers were used in early Cold War Nuclear research. Reg is the geophysics guy... and they were used in geophysics too.
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Bandwidth vs rise time of digital 'scopes: Behavior of the TDS3054
Inspired by recent postings in this group, I've decided to describe my experience with a TDS3054 and a TDS3054B.
These 'scopes have a published bandwidth of 500 MHz on all channels.
The TDS3000-series Service Manual (071-0382-01) on page 1-3 mentions a *calculated* rise time of 700 ps.
This complies with BW = 350/tr (BW in MHz, tr in ns).
350 is the accepted number for analog 'scopes (Gaussian fall-off). Apparently, Tek didn't want to use the larger (400 - 450) value that makes sense for digital 'scopes with their much steeper fall-off.
I measured both TDS 'scopes to indeed have about 700 ps rise time on all four channels, with only a few percent overshoot, in line with the rise time as per the specifications (although mentioned there as calculated).
Two interesting things:
- Both TDS 'scopes have their -3 dB points clearly above 600 MHz on all four channels! If this applies to "all" samples of this model, it indicates that 400 - 420 would be more applicable than 350 but Tek decided in their sales documentation to do as if the number 350 that everybody knows from the analog age would apply, calculating BW from tr. The assumption "Nobody is interested in BW, rise time is what counts" wouldn't be surprising in these digital times.
- Tek sold a TDS3064 having a BW spec. of *600 MHz* with V/div. settings that nicely match my checking results for the two TDS3054's!
AFAIK, checking and (automatically) calibrating frequency behavior in these 'scopes is done by adjusting the step behavior.
Any comments?
Raymond
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Re: User Experience of Sampling Scopes
On Sat, Jan 30, 2021 at 01:18 PM, Miguel Work wrote:
In the video
Yes.. that's it... you can't forget that screen. Thanks for the video. I've got 7S11 and 7T11 in a 7603, and some sampling heads...but, I don't know where... and I haven't fired it up for a few years.
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Typo: ¡°SG503¡± should be SG504. The former does the sensing inside the instrument and obligates you to buy an expensive cable to keep leveling quality all the way to the end of the cable. The SG504 puts the sensor at the point of delivery.
Sent from my iThing, so please forgive typos and brevity.
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On Jan 31, 2021, at 2:37 PM, Tom Lee <tomlee@...> wrote:
?Jean-Paul,
He has said explicitly that he used an HP8657B generator. It is a leveled instrument.
He made measurements on several scopes. Those measurements made sense.
I think it is safe to assume that he made the measurements correctly. Whatever errors he might have as a result of cable type, etc. must be small. And in any case, they were small enough to measure a 600MHz bandwidth. It is hard to contrive a scenario where he has an error that shows up only at 275MHz for that one scope, while all others look good.
Help to solve his bandwidth deficit should focus on the scope that uniquely fell short of specification, not on fixturing details, nor on the type of generator used. The leveling loop in that HP sig gen is as good as it gets for a generator that controls level at its output port. The only difference between it and the 503 is that the latter senses level at point of delivery, so the cabling matters less. Again, he¡¯s already successfully measured a 600MHz bandwidth for another scope using the same setup, so the probability that he has a leveling problem is small enough to look elsewhere.
Tom
Sent from my iThing, so please forgive typos and brevity.
On Jan 31, 2021, at 2:23 PM, Jean-Paul <jonpaul@...> wrote:
?Rebonjour, further musings.....
1/ We use a leveled sine cal generator, eg Tek SG503,SG504 etc or HP 8640B to check BW.
2/ less is more... Eliminate cables if possible, the excellent Leo Bodnar 40 ps pulser has a BNC female to connect directly to a 50ohm scope input.
3/ For 1 M ohm input scopes, Feedthru terms are not perfect, we have some old ones or Chinese clone junk that are NOT good above 100 MHz, we recommend the Tektronix BNC 50 ohm feedthru, or the Mini-Circuits
4/ Tweaking transient response is an art not a science, use care, patience and compromise.
5/ like any amplifier, a scope vertical amp can have non-linearity. The response ( transients or BW) may change depending upon the trace positon on the screen.
Enjoy, and happy tweaking!
Amenities et cordialement,
Jon
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Thanks Jon but I am not looking for accurate calibration.? After reading the manual a few times I see there are three adjustments for each channel.? So when I feel motivated I will look for them and try a tiny tweak to see what happens.
What I basocally want is for the -3 dB frequency to be above 300 MHz.? With three adjustments per channel I can see how I could get into a lot of trouble.? I don't want certified calibration so maybe I can boost the -3 dB frequency a little.? It's not terribly important.
Bob
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On Sunday, January 31, 2021, 02:23:28 PM PST, Jean-Paul <jonpaul@...> wrote:
Rebonjour, further musings.....
1/ We use? a leveled sine cal generator, eg Tek SG503,SG504 etc or HP 8640B to check BW.
2/ less is more... Eliminate cables if possible, the excellent Leo Bodnar 40 ps pulser has a BNC female to connect directly? to a 50ohm scope input.
3/ For 1 M ohm input scopes, Feedthru terms are not perfect, we have? some old ones or Chinese clone junk that are NOT good above 100 MHz, we recommend the Tektronix BNC 50 ohm feedthru, or the Mini-Circuits
4/ Tweaking transient response is an art not a science, use care, patience and compromise.
5/ like any amplifier, a scope vertical amp can have non-linearity.? The? response ( transients or BW) may change depending upon the trace positon on the screen.
Enjoy, and happy tweaking!
Amenities et cordialement,
Jon
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Jean-Paul,
He has said explicitly that he used an HP8657B generator. It is a leveled instrument.
He made measurements on several scopes. Those measurements made sense.
I think it is safe to assume that he made the measurements correctly. Whatever errors he might have as a result of cable type, etc. must be small. And in any case, they were small enough to measure a 600MHz bandwidth. It is hard to contrive a scenario where he has an error that shows up only at 275MHz for that one scope, while all others look good.
Help to solve his bandwidth deficit should focus on the scope that uniquely fell short of specification, not on fixturing details, nor on the type of generator used. The leveling loop in that HP sig gen is as good as it gets for a generator that controls level at its output port. The only difference between it and the 503 is that the latter senses level at point of delivery, so the cabling matters less. Again, he¡¯s already successfully measured a 600MHz bandwidth for another scope using the same setup, so the probability that he has a leveling problem is small enough to look elsewhere.
Tom
Sent from my iThing, so please forgive typos and brevity.
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On Jan 31, 2021, at 2:23 PM, Jean-Paul <jonpaul@...> wrote:
?Rebonjour, further musings.....
1/ We use a leveled sine cal generator, eg Tek SG503,SG504 etc or HP 8640B to check BW.
2/ less is more... Eliminate cables if possible, the excellent Leo Bodnar 40 ps pulser has a BNC female to connect directly to a 50ohm scope input.
3/ For 1 M ohm input scopes, Feedthru terms are not perfect, we have some old ones or Chinese clone junk that are NOT good above 100 MHz, we recommend the Tektronix BNC 50 ohm feedthru, or the Mini-Circuits
4/ Tweaking transient response is an art not a science, use care, patience and compromise.
5/ like any amplifier, a scope vertical amp can have non-linearity. The response ( transients or BW) may change depending upon the trace positon on the screen.
Enjoy, and happy tweaking!
Amenities et cordialement,
Jon
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Re: User Experience of Sampling Scopes
On Sat, Jan 30, 2021 at 12:40 PM, Jeff Dutky wrote:
Can anyone tell me if this is also true on the 11000-series scope, or do they
keep the individual, sampled dots in the final display?
Reg can tell you.
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Re: User Experience of Sampling Scopes
On Sat, Jan 30, 2021 at 09:28 AM, Dave W1BVV wrote:
W2EAW as an application engineer
Hi W1BVV, Dave: Yes, I think many Tekscopers know he works for Tektronix... and also is involved in the ARRL. I probably watched every video he ever posted (mostly directed towards Ham radio)... I can't recall any of one of them that discussed sampling oscilloscopes. Probably, I'm the one that is confused. Can you explain what sampling oscilloscope are? Best regards. Roy
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Rebonjour, further musings.....
1/ We use a leveled sine cal generator, eg Tek SG503,SG504 etc or HP 8640B to check BW.
2/ less is more... Eliminate cables if possible, the excellent Leo Bodnar 40 ps pulser has a BNC female to connect directly to a 50ohm scope input.
3/ For 1 M ohm input scopes, Feedthru terms are not perfect, we have some old ones or Chinese clone junk that are NOT good above 100 MHz, we recommend the Tektronix BNC 50 ohm feedthru, or the Mini-Circuits
4/ Tweaking transient response is an art not a science, use care, patience and compromise.
5/ like any amplifier, a scope vertical amp can have non-linearity. The response ( transients or BW) may change depending upon the trace positon on the screen.
Enjoy, and happy tweaking!
Amenities et cordialement,
Jon
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Re: For Sale T5330-P2 CRT
Shalopt,
Please provide contact information so interested parties can contact you OFF-LIST.
Dennis Tillman W7pF
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of shalopt via groups.io Sent: Sunday, January 31, 2021 1:21 PM To: [email protected]Subject: [TekScopes] For Sale T5330-P2 CRT T5330-P2 CRT same as T64, T533 heater checks good. I have had this for 20 plus years stored in my attic. Acquired at a meteorology auction where I worked, I never had a need. So open to offers ask $40.00 plus shipping. Tubes weighs 40 oz packing additional. Contact me off list if you need. Can provide photos. -- Dennis Tillman W7pF TekScopes Moderator
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Re: User Experience of Sampling Scopes
On Sun, 31 Jan 2021, 22:42 snapdiode via groups.io, <snapdiode= [email protected]> wrote: Well, not to be "that guy", but the SD-24 uses 3.5mm connectors...
Compatible with SMA but not the same.
I have a confession to make. I am "that guy". The one who commits sacrilege by using cheap Chinese SMA connectors and cables with his 20GHz wonder-scope. And they're just fine for my needs, and they fit in my budget. The work the CSA803A does is a small part of my business so I can't justify spending lots to eke out every last picosecond. Trouble is, I live in a place which doesn't have hamfests, radio rallies or surplus equipment to speak of. So if I want used high-end gear I have to import it from somewhere which has had a decent electronics/R&D activity for a long time. That usually means USA/UK/Germany, and it's just not worth it to track down all the little bits and pieces which would be so easy to find at a rally, sadly.
And I would just like to add that I have a S-52 which makes me *almost* as
cool.
Much cooler, I reckon! Chris
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Re: User Experience of Sampling Scopes
Thanks for being ¡°that guy¡±. Not being aware of the difference can cause expensive damage, and it¡¯s one of my pet peeves.
The two connectors can mate, but the 3.5mm connector is made to much tighter tolerances. It also has an air dielectric. Mating to a poorly made (or badly abused) SMA can wreck a 3.5mm connector¡¯s ability to maintain low SWR all the way out to its TEM limit. Permanent damage can be done by a single connect-disconnect cycle.
I have sacrificial connector savers on all of my expensive gear, but occasionally a student will remove them ¡ª against the rules ¡ª to shorten a path or because they think the savers are introducing some artifacts. If they then connect a random SMA cable to the gear, those students have their lab access cards deactivated pretty quickly.
¡ª°ä³ó±ð±ð°ù²õ
Tom
Sent from my iThing, so please forgive typos and brevity.
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On Jan 31, 2021, at 1:42 PM, snapdiode via groups.io <snapdiode@...> wrote:
?Well, not to be "that guy", but the SD-24 uses 3.5mm connectors... Compatible with SMA but not the same.
And I would just like to add that I have a S-52 which makes me *almost* as cool.
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Re: User Experience of Sampling Scopes
Yes, from what I understand, SMA (usually rated to 18 GHz), with its teflon dielectric, and 3.5 mm (26.5 GHz) and 2.92 mm (40 GHz; AKA K connector), with their air dielectrics, are mechanically compatible.
Whereas the 2.4 mm (50 GHz) and 1.85 mm (67 GHz; AKA V connector) are mechanically compatible with each other but not with the SMA/3.5 mm/2.92 mm connectors. Not sure about the 1.0 mm (110 GHz), the new German 1.35 mm (86 GHz), and the crazy expensive 0.9 mm and 0.8 mm jobs. Last I knew, a 1.0 mm connector was about $1000, so not too many people have them! The only ones I have hands-on experience with (so far) are SMA and 3.5 mm connectors. $ = f^n. I don't know what n is, but it's definitely greater than 1, and probably >2.
Yep, I have an S-52 as well, but no S-6 to make a TDR yet. Darn! Had a CSA803 at work back in the day with at least one SD-24. I remember those 3.5 mm connectors. Got to be careful with them, as their center conductors can get out of alignment or broken easily.
Jim Ford
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------ Original Message ------ From: "snapdiode via groups.io" <snapdiode@...> To: [email protected]Sent: 1/31/2021 1:42:00 PM Subject: Re: [TekScopes] User Experience of Sampling Scopes Well, not to be "that guy", but the SD-24 uses 3.5mm connectors... Compatible with SMA but not the same.
And I would just like to add that I have a S-52 which makes me *almost* as cool.
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On Sun, Jan 31, 2021 at 10:22 PM, Jean-Paul wrote:
Notice that a "short legnth of RG/58" is unsuitable for accurate calibration.
A precision 50 cm 50 Ohm like Tektronix 012-0482-00 is preferred.
finally a wideband 10-20 db in-line 50 ohm attenuator like Mini-Circuits
HAT-20 can reduce VSWR reflections that affect the measurements.
A Tek SG504 does a pretty good job as well. Raymond
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Re: User Experience of Sampling Scopes
On Sun, Jan 31, 2021 at 10:09 PM, Miguel Work wrote:
These page may be of your interest:
Thanks Miguel, interesting! Raymond
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Re: User Experience of Sampling Scopes
Well, not to be "that guy", but the SD-24 uses 3.5mm connectors... Compatible with SMA but not the same.
And I would just like to add that I have a S-52 which makes me almost as cool.
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Most 7000 series scopes that have readout seem to have a little switch on the readout board that selects whether the readout is sharing the display with the traces, or has its own time slot after the sweep is finished. Perhaps your switch has become intermittent? -Chuck Harris [email protected] wrote:
I feel like this has been discussed before, but I cannot find the thread now. Does anyone know of a solution for the 7104 readout not displaying except in "pulsed" mode when slaved to the gate (also works in manual)? Mine started doing this, and I have found very little information about it on the internet.
Thanks!
Sean
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And on the subject of Tek vs. HPAK, at work at Raytheon (back when I was traveling there every day before the end of March last year), I noticed that we had Keysight do the calibration of all the MTE (Measurement and Test Equipment, the aerospace and defense term for it), including the Tek scopes. It made me wonder if the Keysight techs didn't intentionally tweak the Tek scopes to just barely meet the specifications! Versus making the HPAK gear exceed the specs!
Enquiring minds want to know!
Jim Ford
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------ Original Message ------ From: "Raymond Domp Frank" <hewpatek@...> To: [email protected]Sent: 1/31/2021 12:32:25 PM Subject: Re: [TekScopes] bandwidth On Sat, Jan 30, 2021 at 11:32 PM, Bob Albert wrote:
HP 54542A spec 500 MHz, measured 600 MHz
Tek 2445 spec 150 MHz, measured 160 MHz
Tek 2440 spec 300 MHz, measured 270 MHz
I guess the Tek 'scopes don't like HP sine waves quite as much.
Raymond
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Re: NEW TOPIC: Outstanding Rockland Instruments 7000 Plugin; WAS: Slightly OT- Wavetek 7530B?
Hi Christian,
Thank you for your fascinating comments, particularly since you are so intimately involved in designing similar instruments for your research in Infrared Atmospheric and Solar Physics. As head of the GIRPAS Laboratory at the Universit¨¦ de Li¨¨ge I can imagine you are quite busy.
Until you mentioned them I had forgotten about the Digital Synthesizers Rockland Instruments engineers designed. These were also state of the art signal sources in their day. I own two of their 1MHz Digital Synthesizers which I used to learn more about spectrum analyzer resolution and phase comparator circuit design. When you have a pair of these synthesizers locked to a Rubidium Frequency Standard it makes it easy to change a 1MHz signal in 1milliHz increments and observe some fascinating details of how phase detector circuits work in slow motion.
The Tektronix 7L5 and the Rockland Instruments 7530A and 7530B Spectrum Analyzers are so fundamentally different that apart from a few basic specifications they can't be compared to each other.
There is something you may have overlooked about the 7530A/B that is not apparent from the schematics which may have been useful when you were searching for the ghost in your spectra that you mentioned. If I remember correctly the specified resolution of the 7530 was 1Hz anywhere in the 100KHz range of the instrument. BUT, unlike Tektronix, Rockland Instruments engineers recognized the importance of designing their instrument to be useful in ways they could not anticipate. They included a front panel connector on the instrument which gave the user access to internal signals. Among other things this allowed the user, by supplying a different clock signal, to increase or decrease the resolution of the instrument. For instance it was possible to increase the resolution from 1Hz to 0.1Hz by reducing the 100KHz bandwidth to 10KHz. I don't think it is possible for a swept IF SA to ever reach that kind of resolution. On the other hand it is quite easy for a Fourier Transform SA to do even better than that.
From your infrared research I was wondering if you are familiar with is the Tektronix J20 / 7J20 Rapid Scan (Optical) Spectrometer. It is capable of scanning the optical spectrum from 250nm (ultraviolet) to 1100nm (near infrared). It can scan any 400nm wide segment of the spectrum in as little as 10mSec. It displays the result as time-resolved spectral power (incident optical power versus wavelength). It has a resolution of 0.25nm.
Dennis Tillman W7pF
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-----Original Message----- From: [email protected] [mailto: [email protected]] On Behalf Of santa0123456 Sent: Sunday, January 31, 2021 1:55 AM To: [email protected]Subject: Re: [TekScopes] NEW TOPIC: Outstanding Rockland Instruments 7000 Plugin; WAS: Slightly OT- Wavetek 7530B? Hello, I followed this discussion and had a look at the 7530A schematic. My job as a physicist deeply involved in electronics is very high resolution spectroscopy of the atmosphere to follow the evolution of its constituents. Since we are using Fourier transform spectrometers with about up to 8 Million points resolution and I am developing these instruments for 3600m altitude observatory, you will understand why I opened this funny schematic. When I was finishing what is now called my 'Master', my work (=challenge) was to develop a digital filter that was inserted between the then crazy 16bit @ 100Ks/S ADCs to keep only the frequency band of interest and undersample the data to reduce the computation work for the big FFT. At that time, on a 1000F HP mainframe, a one Megapoint FFT took 45 minutes mostly due to heavy hard disk swaps. Memory was small and very very expensive... My digital filter used a specialized computing hardware like TRW 16x16 bit MACs, ECL RAMs, etc... All this under the slower supervision of a Z80 that would prepare the sequencing of the filtering process (convolution) and the necessary operator vector coefficients. My school friend and now married with my cousin worked on a similar project for making much faster FFTs because 64Kbit RAMs had emerged. He moved to JPL where he is still doing kind of the same job now before the FFT project could find its end. I still have a pile of 64Kbit RAMs and ALUs at hand. All this to say that I recognize in the Rockland schematic an architecture like the one I devised in 1981. The 'slice processor' looks mostly like an ALU whose control signals come from the sequencer. Sine/Cosine coefficients come from roms and a processor with its attached usual logic prepares all the controls (ALU sequencing, acquisition, display) for the chosen analysis parameters. So, in a sense, the slice bit stuff is not up to the level of a CPU but of a tweaked and specialized ALU. There is therefore probably no assembly language to analyze here but only digital controls for counters, latches, etc. A state machine preprogrammed by the 8080 will provide this bunch of words which is equivalent in a sense to a raw cpu internal microcode but not decoded from higher level instructions. For the story, when I was making the dgital filter, our experimental Fourier-transform spectrometer used two Rockland 8MHz digital synthesizers to generate movement control frequencies millihertz apart. This was also an exceptional device for 1980 and is what we now call a DDS that we can buy for one buck or build in seconds in an FPGA with standard IP building blocks. I remain however doubtful that, at that time with a 12 bit composite ADC and limited memory, the digital approach was giving a real advantage over a 7L5. A few years ago, I had to search for the source of a ghost in our spectra. I tried to use the 7L5 because it is not tied to any of my interferometer controls and works in (slow) real time. I could, just hardly but I could, find this elusive signal when the 'patient' under scrutiny was itself an FFT spectrum analyzer with the usual 2M points @ 18 bits data set. So, a 7L5 remains for me quite a nice and respectable beast at low frequency. For those interested : -- Dennis Tillman W7pF TekScopes Moderator
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Bonjour ¨¤ tous
Tek CAL for the 246xB, wideband plug-ins like 7A29, (and perhaps the models you mention) uses a fast rise pulser like old Tek TD pulsers or PG 506, to trim the transient response at various time scales.
The BW is not calibrated but is a performance check.
Filter theory and analysis shows the trade-off between frequency response and transients response, you can choose one to optimize but not both.
In our work the transient response is critical.
Notice that a "short legnth of RG/58" is unsuitable for accurate calibration. A precision 50 cm 50 Ohm like Tektronix 012-0482-00 is preferred.
finally a wideband 10-20 db in-line 50 ohm attenuator like Mini-Circuits HAT-20 can reduce VSWR reflections that affect the measurements.
Bon Chance
Jon
I await the wise council of our Tek mavens like Dennis T and Chuck H.
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Raymond Domp Frank
Jean-Paul