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
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-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Raymond
Domp Frank
Sent: Sunday, May 13, 2018 9:23 AM
To: [email protected]
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:
/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
