Topics

7T11 sampling timebase - how does it behave?

cmjones01
 

Are there any people on here familiar with the operation of the 7T11/7S11 sampling plugins? The reason I ask is because I'm curious about how the 7T11 actually behaves in operation, because I'm trying to understand how their USSR counterparts, the Ya4S-100 and Ya4S-101 work.

I don't yet have the sampling head for the Ya4S-100, so I'm driving somewhat blind though everything seems to work and I get promising-looking patterns of dots on the screen.

The Ya4S-101 sampling timebase looks very similar to the Tek 7T11. The way it behaves appears to be that the outer time/div knob (labelled 'range' in Russian) selects a time span for the whole screen when the sweep is in 'main' mode. There's a 'delay' knob which moves an intensified portion along the trace, just like a regular dual timebase. The length of the intensified part depends on the position of the inner time/div knob, down to 10ps/div. Pressing the top button to change from 'main' to 'strike' (translated from Russian) mode makes the intensified portion disappear so I assume it's then 'zooming in', again like a regular delayed timebase.

Does the 7T11 behave anything like this? I've never used one.

An additional mystery is that the Ya4S-101 has a second intensified portion of the trace which is moved by a digital up/down nudge control, up to one division later than the first intensified portion. What that does in 'strike' mode I've no idea. Why would it be useful to intensify two portions of the trace, but only up to one division apart? Odd.

Chris

 

Hi Chris,
No, there is no delayed capability in the 7T11/7S11.
There is delayed capability in the 7S14 dual trace dual timebase plugin but the 7S14 only goes to 1GHz.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of
cmjones01
Sent: Tuesday, May 08, 2018 12:16 PM
To: TekScopes@groups.io
Subject: [TekScopes] 7T11 sampling timebase - how does it behave?

Are there any people on here familiar with the operation of the 7T11/7S11
sampling plugins? The reason I ask is because I'm curious about how the
7T11 actually behaves in operation, because I'm trying to understand how
their USSR counterparts, the Ya4S-100 and Ya4S-101 work.

I don't yet have the sampling head for the Ya4S-100, so I'm driving
somewhat blind though everything seems to work and I get promising-looking
patterns of dots on the screen.

The Ya4S-101 sampling timebase looks very similar to the Tek 7T11. The way
it behaves appears to be that the outer time/div knob (labelled 'range' in
Russian) selects a time span for the whole screen when the sweep is in
'main' mode. There's a 'delay' knob which moves an intensified portion
along the trace, just like a regular dual timebase. The length of the
intensified part depends on the position of the inner time/div knob, down
to 10ps/div. Pressing the top button to change from 'main' to 'strike'
(translated from Russian) mode makes the intensified portion disappear so I
assume it's then 'zooming in', again like a regular delayed timebase.

Does the 7T11 behave anything like this? I've never used one.

An additional mystery is that the Ya4S-101 has a second intensified portion
of the trace which is moved by a digital up/down nudge control, up to one
division later than the first intensified portion. What that does in
'strike' mode I've no idea. Why would it be useful to intensify two
portions of the trace, but only up to one division apart? Odd.

Chris



--
Dennis Tillman W7PF
TekScopes Moderator

cmjones01
 

On Tue, May 8, 2018 at 01:42 pm, Dennis Tillman W7PF wrote:
Hi Chris,
No, there is no delayed capability in the 7T11/7S11.
There is delayed capability in the 7S14 dual trace dual timebase plugin but
the 7S14 only goes to 1GHz.
Thank you for that, Dennis. I had a look at the 7T11's manual last night and can see that it only has a single 'timebase' though with a trigger delay adjustment. It looks like the Soviet sampling timebase behaves more like the 7S14.

Chris

Roger Evans
 

Chris, Dennis,
I wondered why the 7S14 had the delayed timebase and Vernier control of the delta-delay markers but this was omitted on the 7T11. There could be several possible reasons and Dennis may be able to point to the truth.

The 7S14 has a delay line so that you can see the trigger point and make accurate time measurements from the trigger to other features on the waveform. On the 7T11 in sequential scan you are looking 10s of nsec after the trigger so you largely lose any time reference from the trigger event.

Another very good reason might be that the 7T11 is already very well filled with multiple boards.

Roger

 

On Wed, May 9, 2018 at 12:07 pm, Roger Evans wrote:


The 7S14 has a delay line so that you can see the trigger point and make
accurate time measurements from the trigger to other features on the waveform.
On the 7T11 in sequential scan you are looking 10s of nsec after the trigger
so you largely lose any time reference from the trigger event.
The 7S14 is specified to "only" 1 GHz. It's very much easier to make a low-distortion (amplitude, phase) delay line for frequencies up to 1 GHz than up to say 11 or 14 GHz, which is where the 7T11 is often used.
The delay line affects the signal in the vertical stage (that would have to be e.g. the 7S11), not in the time base (7T11), so available space in the 7T11 would not be a factor.
It's not in fact the delay line that is used for making accurate time measurements like the 7S14 can; it's the accuracy of the delayed-time-base circuits that do, by showing(/measuring) the delay from one event to another. The 7S14 has a fixed delay time for the signal in the vertical circuits to make it arrive on the plates long enough after the trace starts to make it visible, like in a normal analog 'scope with vertical delay line. The 7T11 in sequential trigger mode has its special way of delaying the display of the vertical signal: It shows parts of many trigger events that happen at least one period (or triggering edge) after the actual events (one event per dot). The setting applies the same (>1 period) delay for each dot.

Raymond

Dave Wise
 

I question one point, Raymond. The 7S14's delay line delays the signal long enough for the rising edge to hit the sampling gate - not the CRT - after the trigger. That's what you meant, right?

Dave Wise
________________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Raymond Domp Frank <@Raymond>
Sent: Wednesday, May 09, 2018 2:29 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7T11 sampling timebase - how does it behave?

On Wed, May 9, 2018 at 12:07 pm, Roger Evans wrote:


The 7S14 has a delay line so that you can see the trigger point and make
accurate time measurements from the trigger to other features on the waveform.
On the 7T11 in sequential scan you are looking 10s of nsec after the trigger
so you largely lose any time reference from the trigger event.
The 7S14 is specified to "only" 1 GHz. It's very much easier to make a low-distortion (amplitude, phase) delay line for frequencies up to 1 GHz than up to say 11 or 14 GHz, which is where the 7T11 is often used.
The delay line affects the signal in the vertical stage (that would have to be e.g. the 7S11), not in the time base (7T11), so available space in the 7T11 would not be a factor.
It's not in fact the delay line that is used for making accurate time measurements like the 7S14 can; it's the accuracy of the delayed-time-base circuits that do, by showing(/measuring) the delay from one event to another. The 7S14 has a fixed delay time for the signal in the vertical circuits to make it arrive on the plates long enough after the trace starts to make it visible, like in a normal analog 'scope with vertical delay line. The 7T11 in sequential trigger mode has its special way of delaying the display of the vertical signal: It shows parts of many trigger events that happen at least one period (or triggering edge) after the actual events (one event per dot). The setting applies the same (>1 period) delay for each dot.

Raymond

 

Regarding the differences between the 7S14 and the 7S11/7T11:

As near as I can tell from using the 7S14 extensively, anyone familiar with any very common dual trace dual timebase Tek product would instantly be familiar with how to use the 7S14. It was extremely easy to use and it worked exactly as it appeared to suggest from looking at it. I looked forward to using 7S14s every opportunity I could before I got a 7104/7A29/7B10/7B15.

As an extensive user of the 7S11/7T11 (I own 6 7S11s 4 7T11s, and 2 7T11As) they are awful to use, they take at least a half hour to get working together, and you often have to confirm a setup first on a 7A29/7B10 to be sure you eliminate anything that can possibly be causing the sampling plugins to not work in spite of you doing everything right. Finally, the amplitude noise of the S4 (I have 3 of them) is more than 2mV and the time jitter of the 7T11s is so great that you can't use them on the most sensitive vertical setting or on the fastest two horizontal settings. These two plugins are a nightmare to use.

I don't believe you can get a clean trace at 2mV/Div and 10pSec/Div or even 20pSec/Div using these plugins. I would love to be proved wrong. If you have proof send me a photograph (@Dennis_Tillman_W7pF) and tell me how you did it. I would love to know how to do it.

Dennis Tillman W7PF

-----Original Message-----
Roger Evans Sent: Wednesday, May 09, 2018 12:08 PM

Chris, Dennis,
I wondered why the 7S14 had the delayed timebase and Vernier control of the
delta-delay markers but this was omitted on the 7T11. There could be
several possible reasons and Dennis may be able to point to the truth.

The 7S14 has a delay line so that you can see the trigger point and make
accurate time measurements from the trigger to other features on the
waveform. On the 7T11 in sequential scan you are looking 10s of nsec after
the trigger so you largely lose any time reference from the trigger event.

Another very good reason might be that the 7T11 is already very well filled
with multiple boards.

Roger


--
Dennis Tillman W7PF
TekScopes Moderator

 

On Wed, May 9, 2018 at 02:47 pm, Dave Wise wrote:


I question one point, Raymond. The 7S14's delay line delays the signal long
enough for the rising edge to hit the sampling gate - not the CRT - after the
trigger. That's what you meant, right?
Yes, Dave, that is sort of what I meant. In my description, I meant to indicate the ultimate goal, which is to show the vertical signal on the crt long enough after the triggering event but maybe I didn't make things as clear as I should have. The delay line has to be positioned *before* the sampling gate i.e. in the analog part, because after the sampling gate the signal isn't an *analog* representation of the input signal anymore nor even a sequence of points of the same edge but a sequence of sampled points on (usually) subsequent edges. So, the analog signal is delayed by the delay lines (one for each channel, DL1 and DL2 in the Service Manual) before being "chopped into pieces". In the SM you can see the "trigger pickoff" (CH1 only) right after the compensation circuits. These serve to compensate for the adverse phase and amplitude effects of the delay line on the signal - and on the input impedance. The trigger signal is output to the horizontal (ramp) circuits on J50.

Raymond

 

Dennis,

As an extensive user of the 7S11/7T11 (I own 6 7S11s 4 7T11s, and 2 7T11As) they are awful to use
I don't fully agree with you on this, Dennis. Whereas the 7S14 behaves almost exactly like an analog 'scope, as you describe, the 7S11/7T11 behaves very differently. Although it (actually, mostly the 7T11) does remain a bit finicky to use, the most important thing I guess before using the 7S11/7T11 is realising it's not a general purpose 'scope setup, taking a deep breath and letting go of the assumption that the time settings are some sort of equivalent to normal time base setting (s/div.) with an ordinary time-expanded window in it, like with a second (delayed) time base. I do agree that triggering effort, noise level etc. do remain less pleasant than when using a 7S14 or a 7104 equipped as you mention. OTOH, no amount of effort will show an 8 GHz waveform on the 7S14 or 7104 - or a 50 ps step with any fidelity. I get quite good results with a 7S11/S-4/7T11A in a 7854, using digital storage and filtering, though I haven't exactly tried things like your 10 ps/div or 2 mV/div. I might give that a try though, one of these days with the 7854.
Not only have I had fun playing with the 7S11/7T11 but I have had results as well; one does get used to them. As an example, I certainly prefer adjusting the fast edge of a PG-506 using a 7S11/7T11 over a 7104 or 7S14... Signal fidelity (shape and speed) cannot be matched by either of the two latter setups. And I cannot judge the performance of my home-made TD-pulser without the 7S11/S-4/7T11 setup.

Raymond

 

IIRC, the 7T11 has a Random Sampling mode; the dots on screen are not sequential.
Instead, the sampling window is intentionally jittered horizontally.
This allows you to see the trigger point without the need for a delay line, which would reduce the bandwidth.
Keep an eye out for a Tek Concepts book on sampling scopes.

HankC, Boston, WA1HOS

Craig Sawyers <c.sawyers@...>
 

IIRC, the 7T11 has a Random Sampling mode; the dots on screen are not sequential.
Instead, the sampling window is intentionally jittered horizontally.
This allows you to see the trigger point without the need for a delay line, which would reduce the
bandwidth.
Keep an eye out for a Tek Concepts book on sampling scopes.

HankC, Boston, WA1HOS
I have a complete set of Concepts books, including the one on sampling, which I have read cover to
cover several times. But random sampling on the 7T11 is even worse than sequential sampling regarding
getting a useable trace. Often the dots are widely spaced and (of course, given the mode) jittering
around. Identifying anything that looks like a rising edge is usually a forlorn task.

Craig

 

HankC,

IIRC, the 7T11 has a Random Sampling mode; the dots on screen are not sequential.
The 7T11 does indeed have a second "Random Sampling" mode, which is very different from the regular mode and more difficult to adjust and use.
The dots on the screen are sequential (otherwise, you wouldn't see the waveform) but their acquisition is not.
The regular mode is much more like the way that the 7S14 does its acquisition.

Raymond

 

Hu Raymond,

I have often described the 7S11/7T11 as finicky. Its more than a bit finicky as you seem to feel. After reading your comments I finally went looking for the source of my frustration with the 7S11/7T11. My main complaint has to do with the timebase, triggering, time jitter and the overall way the 7T11/7T11A works. I spend almost no time setting up the 7S11.

My biggest complaint with the 7T11 (and where some of my finicky description comes from) is the lack of a trigger light. Why doesn't it have one? That would make a huge difference in usability. Most of the time I am turning knobs in hope something, anything, appears on the screen it is because I don't have a clue whether I'm within a decent trigger level or not. My "solution" to that is simple but not foolproof. I ALWAYS use a 7S11/7Tll in the inner two slots in conjunction with a 7A29/7B10 in the two outer slots. The very first test I perform is to apply the signal to the real time plugins to determine the voltage levels, rise times, trigger points etc. Then I set the 7S11/7T11 up as close as possible to those exact settings. That gets me in the ball park and improves my odds of getting the 7T11 to trigger to about 40% of the time. That still leaves a lot of room for improvement.

I looked up the specs for horizontal display jitter since after the lack of a trigger light horizontal (time) jitter is the biggest problem in MOST CASES (more on that below). Here are the 7T11A Specs for Sequential Mode Display Jitter using 50ohm and 1Mohm triggering,: 10ps or less at fastest SWEEP RANGE position (fully CCW): 0.4 divisions or less at remaining six positions of SWEEP RANGE; Measurements made under OPTIMUM TRIGGER CONDITIONS. So it should be 1 division at 10ps/Div and 0.4 divisions at 20ps/Div or slower.

The 7854 is my favorite of all the 7K scopes. Wherever possible I will use it to reduce sampling time jitter. Under IDEAL CONDITIONS the 7854 can reduce the time jitter to 0ps!!! at the 10ps/Div sweep speed. This is another reason to love the 7854.

I'm sure my definition of IDEAL CONDITIONS coincides exactly with Tek's OPTIMUM TRIGGER CONDITIONS. It means there is, according to the 7T11A Sampling Sweep Unit Manual on pg 2-6, "... a signal source that provides a signal for triggering slightly before it delivers an output pulse to the Sampling Head input. A pretrigger lead time of 75nSec is required." Additionally, a signal with a fast repetition rate is desirable.

So last night I thought I would start with an ideal signal source and proceed to lesser and lesser signal sources until I could no longer get a stable display with less than 50pS of time jitter. These tests were performed in Sequential mode.

The ideal source that first came to mind was Leo Bodnar's simple to use Fast Risetime Pulse Generator (FRPG).
<http://www.leobodnar.com/shop/index.php?main_page=product_info&products_id=295>
I'm sure this is what Tek had in mind 45 years ago for their idea of OPTIMUM TRIGGER CONDITIONS. Even without the magic averaging of the 7854 the 7T11A displays about 0.4 divisions of time jitter (it exceeded its spec) from Leo's FRPG on the 10ps sweep speed. Averaging reduces this to 0ps. By my estimate I spent about an hour with Leo Bodnar's FRPG to optimize the display for minimal 7T11A jitter. Risetime of the system [Leo Bodnar FRPG (40ps) + S-4 (25ps)] = ~47ps. I measured 40ps but I believe Leo has been conservative in his specs which I suspect are closer to 30ps.

Next I tested an S-52 Pulse Generator Head in a Type 285 Power Supply. Same result, except for some reason it was harder to optimize the 7T11A for minimum jitter. I spent about 4 hours on this experiment. For some reason it was more finicky than Leo's FRPG. The risetime of the system [S-52 (25ps) + S-4 (25ps)] = ~35ps. Again I measured 40ps.

After this the 7T11A became jumpy for some reason. A rising edge would suddenly jump left or right as much as a division at a time. So I switched to the other 7T11A which wasn't working properly yesterday but which was working today (more finickiness).

For the next test I disconnected the trigger from Leo's FRPG. To my surprise the pulse was as stable as when I used external triggering. Again the time jitter was within spec and reduced to 0ps by the 7854 averaging. As I discovered in the next test the reason why Leo's FRPG works so well without using a trigger signal is because it is a square wave.

For the last test (I had no idea I would reach this point so fast) I tried feeding the S-52 to the 7S11/S-4 but this time there was no external trigger going to the 7T11. Without a trigger the 7T11 would not trigger on the waveform except in slow sweep speeds. The fastest usable speed was 10ns on the 50us range. The reason for this is the unusual shape of the waveform and the double pulse generated by the S-52.

This would explain part of why the 7T11/7T11A is, in my experience, so finicky. I have never had a reason to measure 12GHz sine waves but I imagine the 7T11/7T11A will probably do pretty well with a simple waveform like a sinewave since it does fine with Leo's FRPG square wave.

Dennis Tillman W7PF

-----Original Message-----
From: Raymond Domp Frank, Sent: Wednesday, May 09, 2018 4:21 PM

Dennis,

As an extensive user of the 7S11/7T11 (I own 6 7S11s 4 7T11s, and 2
7T11As) they are awful to use
I don't fully agree with you on this, Dennis. Whereas the 7S14 behaves
almost exactly like an analog 'scope, as you describe, the 7S11/7T11
behaves very differently. Although it (actually, mostly the 7T11) does
remain a bit finicky to use, the most important thing I guess before using
the 7S11/7T11 is realising it's not a general purpose 'scope setup, taking
a deep breath and letting go of the assumption that the time settings are
some sort of equivalent to normal time base setting (s/div.) with an
ordinary time-expanded window in it, like with a second (delayed) time
base. I do agree that triggering effort, noise level etc. do remain less
pleasant than when using a 7S14 or a 7104 equipped as you mention. OTOH, no
amount of effort will show an 8 GHz waveform on the 7S14 or 7104 - or a 50
ps step with any fidelity. I get quite good results with a 7S11/S-4/7T11A
in a 7854, using digital storage and filtering, though I haven't exactly
tried things like your 10 ps/div or 2 mV/div. I might give that a try
though, one of these days with the 7854.
Not only have I had fun playing with the 7S11/7T11 but I have had results
as well; one does get used to them. As an example, I certainly prefer
adjusting the fast edge of a PG-506 using a 7S11/7T11 over a 7104 or
7S14... Signal fidelity (shape and speed) cannot be matched by either of
the two latter setups. And I cannot judge the performance of my home-made
TD-pulser without the 7S11/S-4/7T11 setup.

Raymond



--
Dennis Tillman W7PF
TekScopes Moderator

 

Hi Dennis,
Thanks for the detailed explanation of your experiments.
Most of what you write matches my experience with the 7T11 setup, but for your triggering experience. Although finicky, it is not as much a disaster as you're experiencing. The first thing I always do is adjust the trigger until I get a trace, any trace at all, since without trigger, there's no trace, only a bright, slowly moving dot. I reduce beam intensity to avoid burning the screen. More precise trigger adjustment is to follow once I get to a useful "delay" and sampling speed. Although I also have a standard vertical and horizontal setup in the 4-slot mainframes, I don't remember ever having benefited for setting things up. That's probably because I usually know what to expect with the few sources I use...

For the last test (I had no idea I would reach this point so fast) I tried feeding the S-52 to the 7S11/S-4 but this time there was no external trigger
going to the 7T11. Without a trigger the 7T11 would not trigger on the waveform except in slow sweep speeds. The fastest usable speed was
10ns on the 50us range. The reason for this is the unusual shape of the waveform and the double pulse generated by the S-52.
I have two fast edge generators: My home-built < 200 ps tunnel diode pulser (to be improved) and like you, an S-52. I'm not experiencing serious issues using internal triggering with my S-4, even with the S-52's complicated waveform. I just have to realize that the fast edge starts at a slightly higher level than the slower edges.
I checked my photographs of sampler experiments. I took them a few years ago, in 2012 and 2015, using a 7603. I have no images of using a 7854 in that setup (yet). When I get back to my lab, I'll take a few and post them.
Please have a look at the screen shots from 2012 and 2015: https://groups.io/g/TekScopes/album?id=49077
You'll see the scope and plugins I used. I see no more than 15 - 20 ps jitter p-p, unfiltered. I have several sets of all equipment, which should explain the big difference between the first two images (2012) and the rest, which is from 2015 (!). The early traces look much better, except for the large overshoot. No idea about that, I took them 6 months after I started collecting Tek equipment.

Raymond

 

Hi Raymond,
I looked at the pix. You seem to have 30pSec risetime and I would like to know how you do that since the S4 has a 25pS rise time. That would mean you were using a 13pS pulse.

The 2nd photo must have been on a 7854 since the time jitter at 20ps is almost 0ps.

Your time jitter is about the same as mine and within spec.

You didn't say what your signal source was in any of these photos. Was it the S-52: If so how did you get it to trigger. I was aware that the 2nd pulse was taller and I tried to trigger on it but I could only trigger on both simultaneously which made for a very confusing waveform and a lot of knob twiddling to no avail. I will try it again. I didn't think of using a 2nd 7S11 to power the S-52. Maybe that will work better. Since you powered the S-52 from the 7S11 can you use that 7S11 to provide the triggering for the 7T11/7T11A internally through that 7S11. I see you had no external trigger from the pretrigger output of the S-52 to the external input of the 7T11/7T11A. I was applying the pretrigger from the S-52 to the external trigger of the 7T11/7T11A

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Raymond
Domp Frank
Sent: Sunday, May 13, 2018 9:23 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] 7T11 sampling timebase - how does it behave?

Hi Dennis,
Thanks for the detailed explanation of your experiments.
Most of what you write matches my experience with the 7T11 setup, but for
your triggering experience. Although finicky, it is not as much a disaster
as you're experiencing. The first thing I always do is adjust the trigger
until I get a trace, any trace at all, since without trigger, there's no
trace, only a bright, slowly moving dot. I reduce beam intensity to avoid
burning the screen. More precise trigger adjustment is to follow once I get
to a useful "delay" and sampling speed. Although I also have a standard
vertical and horizontal setup in the 4-slot mainframes, I don't remember
ever having benefited for setting things up. That's probably because I
usually know what to expect with the few sources I use...

For the last test (I had no idea I would reach this point so fast) I
tried feeding the S-52 to the 7S11/S-4 but this time there was no
external trigger going to the 7T11. Without a trigger the 7T11 would not
trigger on the waveform except in slow sweep speeds. The fastest usable
speed was 10ns on the 50us range. The reason for this is the unusual shape
of the waveform and the double pulse generated by the S-52.
I have two fast edge generators: My home-built < 200 ps tunnel diode pulser
(to be improved) and like you, an S-52. I'm not experiencing serious issues
using internal triggering with my S-4, even with the S-52's complicated
waveform. I just have to realize that the fast edge starts at a slightly
higher level than the slower edges.
I checked my photographs of sampler experiments. I took them a few years
ago, in 2012 and 2015, using a 7603. I have no images of using a 7854 in
that setup (yet). When I get back to my lab, I'll take a few and post them.
Please have a look at the screen shots from 2012 and 2015:
https://groups.io/g/TekScopes/album?id=49077
You'll see the scope and plugins I used. I see no more than 15 - 20 ps
jitter p-p, unfiltered. I have several sets of all equipment, which should
explain the big difference between the first two images (2012) and the
rest, which is from 2015 (!). The early traces look much better, except for
the large overshoot. No idea about that, I took them 6 months after I
started collecting Tek equipment.

Raymond



--
Dennis Tillman W7PF
TekScopes Moderator

 

Hi Dennis,
I took a few photographs with current equipment and my previous measurements were largely confirmed. Please refer to the added photographs in the album. Their names indicate what's shown, as opposed to the older photographs which only carry their image number.
I apologise for the disappointing quality of the "rush job".
I used two 'scopes and two S-52's:
- A 7854 with 7T11A, 7S11/S-52 and 7S11/S-4
- A 7904 with 7S12, S-52 and S-6, terminated

You seem to have 30pSec risetime and I would like to know how you do that since the S4 has a 25pS rise time. That would
mean you were using a 13pS pulse.
I'd say slightly more: 36 to almost 40 ps, ignoring the influence of overshoot. The sampling outfits are separate. I've never attempted to adjust the time bases and adjusted the horizontal sensitivity of the mainframes using a Calibration Fixture (067-0587-01), calibrated against a second unit so I'm tempted to trust the measurements. ISTR that Tek specified minimum ("at least") specs for the samplers and pulse generators. I also STR that it was not easy to measure the performance of these heads at the time (state of the art technology) so specs may have been very conservative. You're definitely far more knowledgeable on this than I.

The 2nd photo must have been on a 7854 since the time jitter at 20ps is almost 0ps.
Surprise! I used the High Resolution setting of the 7S12 in the 7603. I repeated it today in the 7904. Please refer to today's picture.

You didn't say what your signal source was in any of these photos. Was it the S-52: If so how did you get it to trigger.
I was aware that the 2nd pulse was taller and I tried to trigger on it but I could only trigger on both simultaneously which
made for a very confusing waveform and a lot of knob twiddling to no avail.
I used two different S-52's, please refer to the new photographs. In the 7T11A setup, I used internal triggering. Only with the trigger amp. on X1 I was able to filter out the one waveform, strangely enough. I remember the same thing from my previous experiments.

Please let me know if you can't derive a setting from the new images in the album.

Raymond

Ed Breya
 

I'd say the 36-40 pSec tr displayed result is in the right ballpark. If the tr of the pulse and the the sampler are both 25 pSec, then the net would be about 35. If they are both 30 pSec, then it would net about 42.

Ed

Albert Otten
 

On Mon, May 14, 2018 at 10:58 am, Raymond Domp Frank wrote:


[Dennis:]
You didn't say what your signal source was in any of these photos. Was it
the S-52: If so how did you get it to trigger.
I was aware that the 2nd pulse was taller and I tried to trigger on it but I
could only trigger on both simultaneously which
made for a very confusing waveform and a lot of knob twiddling to no avail.
I used two different S-52's, please refer to the new photographs. In the 7T11A
setup, I used internal triggering. Only with the trigger amp. on X1 I was able
to filter out the one waveform, strangely enough. I remember the same thing
from my previous experiments.
Hello Raymond,
Two things you didn't mention explicitly but follow from the 7854 photos:
- You used internal triggering. Yes, but not triggering by the S4 (with I previously thought and couldn't understand) but by the S-52 rear pretrigger.
- The S11/S4 is set for Smooth. That explains the smooth curve.
I think Dennis tried to trigger from the S-52 TD output (or internal S-4). In sequential mode that would be problematic since you have to trigger on another edge than the one you want to display. That in turn would require a large Range setting at the 7T11A.

Albert

 

Hello Albert,
- You used internal triggering. Yes, but not triggering by the S4 (with I previously thought and couldn't understand)
but by the S-52 rear pretrigger.
Bingo! The idea was to show the S-52's signal into the S-4 so having the S-52 in the same mainframe with the other stuff made that simple.

- The S11/S4 is set for Smooth. That explains the smooth curve.
Yes and not really: Yes, the 7S11 in the 7854/7T11A/7S11/S4 setup was - inadvertently - set to smooth, and no, what you're seeing is the averaged digital result of 100 samples. You can see it from the readout info and in
the photograph "7854_7T11A_S-4 CRT.jpg". In my experience, smooth won't result in as smooth a trace as that by far.

In the 7904/7S12/S-6, the setting was High Resolution to get the smooth trace.

Raymond

Albert Otten
 

On Mon, May 14, 2018 at 01:29 pm, Raymond Domp Frank wrote:


Hello Albert,
- You used internal triggering. Yes, but not triggering by the S4 (with I
previously thought and couldn't understand)
but by the S-52 rear pretrigger.
Bingo! The idea was to show the S-52's signal into the S-4 so having the S-52
in the same mainframe with the other stuff made that simple.

- The S11/S4 is set for Smooth. That explains the smooth curve.
Yes and not really: Yes, the 7S11 in the 7854/7T11A/7S11/S4 setup was -
inadvertently - set to smooth, and no, what you're seeing is the averaged
digital result of 100 samples. You can see it from the readout info and in
the photograph "7854_7T11A_S-4 CRT.jpg". In my experience, smooth won't result
in as smooth a trace as that by far.

In the 7904/7S12/S-6, the setting was High Resolution to get the smooth trace.

Raymond
Hello Raymond,
I don't see that from the readout or the photo annotation but never mind. I agree that just 7S11 Smooth is probably much less smooth.
BTW with 7854/7S12/S-6 I once measured rise time about 33 ps.
Just for reference here is your album link once more: https://groups.io/g/TekScopes/album?id=49077 .

Albert