Topics

7S12 TDR Cable


Nathan Johnson
 

One of my new scope acquisitions(currently in transit) is coming with a
7S12/S-6/S-52 TDR setup. Of course no cables. Right now I'm looking at the
S-6 manual and looking at the interconnection diagram. It looks like I
should be using the 750ps cable(015-1017-01) and the "Test Line" cable
015-0123-00. Obviously these cables all got lost, and I can't locate any at
the moment. I've saved my searches and will keep an eye out. I'm trying to
understand the requirements of a replacement.
As I understand this, the interconnect cable being of a certain electrical
length was to delay the pulse reaching the S-6 until after the trigger? So
that would be satisfied by anything that delayed at LEAST 750ps? I have
some 6 inch RG-402 jumpers that using book figures for 402, should be
around 780-820ps. Hoping that will work, as I don't have anything to
measure the exact electrical length of a cable... Until I get the TDR
working. Go figure.
The "Test Line" is specced at 1ns, and I assume that this was to make the
interconnection from "trusted test gear" to "circuit under test" a
fixed/known distance from the sampler as well as avoiding too short a cable
total/too short pulse+reflection? I'm thinking that once I get this working
I can use a "roughly 1ns" cable to attach another cable to the end, and
trim to 1ns?
Any idea what the tolerances would be on these cables from the factory?
Nathan KK4REY

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Craig Sawyers <c.sawyers@...>
 

As I understand this, the interconnect cable being of a certain electrical length was to delay the
pulse
reaching the S-6 until after the trigger? So that would be satisfied by anything that delayed at
LEAST
750ps?
No - it is just a practical length of semi-rigid to go from the S52 to the S6. You have to use high
quality semi rigid though - you are trying to get low aberration 25ps rise time through it so
attenuation and return loss are important. This sort of thing
http://194.75.38.69/products/test_flex.shtml from Minicircuits probably the 5" version at $10

The "Test Line" is specced at 1ns, and I assume that this was to make the interconnection from
I think that is just part of the familiarisation - stick an unterminated line on the S6 and watch
the reflection come back.

What you definitely need to do is treat the S6 with utmost respect. They are static sensitive - in
fact Tek did an apps note 42W-5850 "Preventing Sampling Head Damage", and you can destroy an S6 with
static discharge from your finger, or a charged up bit of coax. I keep the inputs of the travelling
wave heads (S4 and S6) with a 50 ohm terminator on the inputs when not in use. I bought a bag of
cheap ones for precisely that. The other thing is to discharge any coax you connect to the input -
just short out ground to centre pin for a second before connecting to your S6.


Nathan Johnson
 

I am well aware of that, I do have a bag of terminations on the way as well. Unfortunately the eBay seller does not know this, and it looks like it will be in transit without termination... So it may be a real miracle if it arrives intact. I take it that the sampler is made out of tiny quantities of unobtainium, no chance for repair if it is screwed up?
Nathan KK4REY

Sent using CloudMagic Email [https://cloudmagic.com/k/d/mailapp?ct=pi&;cv=7.4.15&pv=9.1&source=email_footer_2]
On Mon, Apr 4, 2016 at 18:42, Craig Sawyers' c.sawyers@tech-enterprise.com [TekScopes] <TekScopes@yahoogroups.com> wrote:
As I understand this, the interconnect cable being of a certain electrical length was to delay the
pulse
reaching the S-6 until after the trigger? So that would be satisfied by anything that delayed at
LEAST
750ps?
No - it is just a practical length of semi-rigid to go from the S52 to the S6. You have to use high
quality semi rigid though - you are trying to get low aberration 25ps rise time through it so
attenuation and return loss are important. This sort of thing
http://194.75.38.69/products/test_flex.shtml from Minicircuits probably the 5" version at $10

The "Test Line" is specced at 1ns, and I assume that this was to make the interconnection from
I think that is just part of the familiarisation - stick an unterminated line on the S6 and watch
the reflection come back.

What you definitely need to do is treat the S6 with utmost respect. They are static sensitive - in
fact Tek did an apps note 42W-5850 "Preventing Sampling Head Damage", and you can destroy an S6 with
static discharge from your finger, or a charged up bit of coax. I keep the inputs of the travelling
wave heads (S4 and S6) with a 50 ohm terminator on the inputs when not in use. I bought a bag of
cheap ones for precisely that. The other thing is to discharge any coax you connect to the input -
just short out ground to centre pin for a second before connecting to your S6.





[Non-text portions of this message have been removed]


Craig Sawyers <c.sawyers@...>
 

So it may be a real
miracle if it arrives intact. I take it that the sampler is made out of tiny quantities of
unobtainium, no
chance for repair if it is screwed up?
Mine arrived without too - and survived because the guy at least bagged it in antistatic wrap. And
yes - not a chance of repair - the business end is an alumina thick film hybrid with 6 chip diodes
bonded onto it. It is unlike any conventional sampling bridge - the S4 and S6 work by a fast
travelling wave trapping charge on diodes as it propagates. The 1GHz S1, possibly S2 and definitely
S3 (because I fixed mine when it was DOA) are repairable because fast Agilent surface mount diodes can
be pressed into use. But the S4 and S6 are simply not possible.


Nathan Johnson
 

I assume that a failure would be "digital", either it works or it doesn't? I may have my hopes up a little bit high on this one... Tested working S-6 heads seem to go for more than I paid for the 7854 with all this installed..
Nathan KK4REY

Sent using CloudMagic Email [https://cloudmagic.com/k/d/mailapp?ct=pi&;cv=7.4.15&pv=9.1&source=email_footer_2]
On Mon, Apr 4, 2016 at 18:58, Craig Sawyers' c.sawyers@tech-enterprise.com [TekScopes] <TekScopes@yahoogroups.com> wrote:
So it may be a real
miracle if it arrives intact. I take it that the sampler is made out of tiny quantities of
unobtainium, no
chance for repair if it is screwed up?
Mine arrived without too - and survived because the guy at least bagged it in antistatic wrap. And
yes - not a chance of repair - the business end is an alumina thick film hybrid with 6 chip diodes
bonded onto it. It is unlike any conventional sampling bridge - the S4 and S6 work by a fast
travelling wave trapping charge on diodes as it propagates. The 1GHz S1, possibly S2 and definitely
S3 (because I fixed mine when it was DOA) are repairable because fast Agilent surface mount diodes can
be pressed into use. But the S4 and S6 are simply not possible.


Craig Sawyers <c.sawyers@...>
 

I assume that a failure would be "digital", either it works or it doesn't? I may have my hopes up a
little
bit high on this one... Tested working S-6 heads seem to go for more than I paid for the 7854 with
all
this installed..
Nathan KK4REY
Don't unnecessarily get concerned - it might work just fine and dandy. Mine does, in fact I was using
it today to see precisely how lousy BNC connectors can be.


Nathan Johnson
 

I bought a 7854, two in fact in the past week, mostly because they are high on the want list for my collection, and they came up cheap on eBay. Going to be interesting, both claim to work, but only one was willing to provide images showing the self test completion. The 7854+TDR combo looks really nice on paper, will need to check it out in real life... And learn to use a 7854!
Nathan KK4REY

Sent using CloudMagic Email [https://cloudmagic.com/k/d/mailapp?ct=pi&;cv=7.4.15&pv=9.1&source=email_footer_2]
On Mon, Apr 4, 2016 at 19:09, Craig Sawyers' c.sawyers@tech-enterprise.com [TekScopes] <TekScopes@yahoogroups.com> wrote:
I assume that a failure would be "digital", either it works or it doesn't? I may have my hopes up a
little
bit high on this one... Tested working S-6 heads seem to go for more than I paid for the 7854 with
all
this installed..
Nathan KK4REY
Don't unnecessarily get concerned - it might work just fine and dandy. Mine does, in fact I was using
it today to see precisely how lousy BNC connectors can be.


 

When I tried to send this last night at 7:51PM PST Yahoo rejected it. In
fact it seemed to have been rejecting emails for a few hours.
Dennis

-----Original Message-----
From: Dennis Tillman [mailto:dennis@ridesoft.com]
Sent: Monday, April 04, 2016 7:51 PM
To: 'TekScopes@yahoogroups.com' <TekScopes@yahoogroups.com>
Subject: FW: [TekScopes] 7S12 TDR Cable

Hi Nathan,
TDR is a fascinating world unto its own. There are many things you can do
with it but it is so unlike everything you probably know about electronics
that you will want to get some help. One great source is the Tektronix Time
Domain Reflectrometry Measurements book. It was written in 1970 but
everything in it is still current today.

It is interesting to note that the fastest TDR systems available today are
still only about 50% faster than the 7S12 /S-52 / S-6 system equivalent
risetime of ~30pSec. So, in other words it was an outstanding system in its
day, and it is an excellent system to have today.

Dennis Tillman W7PF

-----Original Message-----
Sent: Monday, April 04, 2016 7:36 AM
Subject: [TekScopes] 7S12 TDR Cable

One of my new scope acquisitions(currently in transit) is coming with a
7S12/S-6/S-52 TDR setup. Of course no cables. Right now I'm looking at the
S-6 manual and looking at the interconnection diagram. It looks like I
should be using the 750ps cable(015-1017-01) and the "Test Line" cable
015-0123-00. Obviously these cables all got lost, and I can't locate any at
the moment. I've saved my searches and will keep an eye out. I'm trying to
understand the requirements of a replacement.
As I understand this, the interconnect cable being of a certain electrical
length was to delay the pulse reaching the S-6 until after the trigger? So
that would be satisfied by anything that delayed at LEAST 750ps? I have some
6 inch RG-402 jumpers that using book figures for 402, should be around
780-820ps. Hoping that will work, as I don't have anything to measure the
exact electrical length of a cable... Until I get the TDR working. Go
figure.
The "Test Line" is specced at 1ns, and I assume that this was to make the
interconnection from "trusted test gear" to "circuit under test" a
fixed/known distance from the sampler as well as avoiding too short a cable
total/too short pulse+reflection? I'm thinking that once I get this working
I can use a "roughly 1ns" cable to attach another cable to the end, and trim
to 1ns?
Any idea what the tolerances would be on these cables from the factory?
Nathan KK4REY
------------------------------------
Posted by: Nathan Johnson <jdownj@gmail.com>
------------------------------------


 

When I tried to send this last night at 8:07PM PST Yahoo rejected it. In
fact it seemed to have been rejecting emails for a few hours.
Dennis

-----Original Message-----
From: Dennis Tillman [mailto:dennis@ridesoft.com]
Sent: Monday, April 04, 2016 8:07 PM
To: 'TekScopes@yahoogroups.com' <TekScopes@yahoogroups.com>
Subject: RE: [TekScopes] 7S12 TDR Cable

Hi Nathan,

One more thing. The 7S12 has a "shoe" on it which allows you to connect a
7S11 to it to add another vertical amplifier to your scope. Ordinarily most
TDR measurements will only involve sending a pulse down a line and measuring
the reflections that come back. But with two vertical channels you can
monitor two ports. This comes in handy for measuring the response of power
splitters or two port devices.

That 7S11 will require a sampling head such as an S-5 25pSec head.

Both the S-6 and the S-5 were designed by the very talented George Frye at
Tektronix back in the late 1960s. George now owns a company that
manufacturers Audiological Test Equipment in Tigard, OR.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@yahoogroups.com [mailto:TekScopes@yahoogroups.com]
Sent: Monday, April 04, 2016 7:36 AM
To: tekscopes@yahoogroups.com
Subject: [TekScopes] 7S12 TDR Cable

One of my new scope acquisitions(currently in transit) is coming with a
7S12/S-6/S-52 TDR setup. Of course no cables. Right now I'm looking at the
S-6 manual and looking at the interconnection diagram. It looks like I
should be using the 750ps cable(015-1017-01) and the "Test Line" cable
015-0123-00. Obviously these cables all got lost, and I can't locate any at
the moment. I've saved my searches and will keep an eye out. I'm trying to
understand the requirements of a replacement.
As I understand this, the interconnect cable being of a certain electrical
length was to delay the pulse reaching the S-6 until after the trigger? So
that would be satisfied by anything that delayed at LEAST 750ps? I have some
6 inch RG-402 jumpers that using book figures for 402, should be around
780-820ps. Hoping that will work, as I don't have anything to measure the
exact electrical length of a cable... Until I get the TDR working. Go
figure.
The "Test Line" is specced at 1ns, and I assume that this was to make the
interconnection from "trusted test gear" to "circuit under test" a
fixed/known distance from the sampler as well as avoiding too short a cable
total/too short pulse+reflection? I'm thinking that once I get this working
I can use a "roughly 1ns" cable to attach another cable to the end, and trim
to 1ns?
Any idea what the tolerances would be on these cables from the factory?
Nathan KK4REY
------------------------------------
Posted by: Nathan Johnson <jdownj@gmail.com>
------------------------------------


 

That 7S11 will require a sampling head such as an S-5 25pSec head
I guess that's an S-4 sampling head ;-(

Raymond


 

Hi Raymond,
Thanks for the correction. You are correct, I meant the S-4 head.
So many heads, so little time to use them all! Sigh!

I even have an S42 Optical to Electrical head which is quite rare. They
couldn't make it fit in the sampling head form factor so they had to make it
an inch longer. As a result it sticks out about an inch from the front of
the 7S11 which makes it look funny / ugly. I imaging this gave Deane Kidd
fits when he had to approve it for final shipment.

I'm finally starting to play with electro-optics so I may have a chance to
use the S-42 head.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@yahoogroups.com [mailto:TekScopes@yahoogroups.com]
Sent: Tuesday, April 05, 2016 1:59 PM
To: TekScopes@yahoogroups.com
Subject: [TekScopes] Re: 7S12 TDR Cable

That 7S11 will require a sampling head such as an S-5 25pSec head
I guess that's an S-4 sampling head ;-(

Raymond





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Posted by: hewpatek@gmail.com
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