Inexpenive 50 Ohm Feed Through Terminations

[joeqsmith]

Are you performing a calibration using the load only?   Does the load and reference have the same connector?  If not, how did you compensate for the difference? 

I wonder, did you happen to save plots for the other resistor combinations you tried?   

I double checked to see if I had saved any of the data I collected back then but came up short. 

[ocw]

I have 7/16" DIN, SMA and N connector calibration kits.  I obviously used the SMA version this time.  I have wondered about your calibration kit.

... the cal standard for my old 8754A is using two 100 ohm 0805's for the load.

A calibration standard will always be measured by the same instrument as being perfect regardless of how good or bad it is.

I provided a link to the manufacturer's RF specifications for the resistor which I suggested.  Where are similar specifications for what you used?

While you are making it difficult, I am trying to be helpful not confrontational.

[joeqsmith]

I have 7/16" DIN, SMA and N connector calibration kits.  I obviously used the SMA version this time.  I have wondered about your calibration kit.

... the cal standard for my old 8754A is using two 100 ohm 0805's for the load.

A calibration standard will always be measured by the same instrument as being perfect regardless of how good or bad it is.

Obviously. 

I provided a link to the manufacturer's RF specifications for the resistor which I suggested.  Where are similar specifications for what you used?

They don't normally provide s-parameters for standard resistors like I have used.  As I mentioned in my previous post, I couldn't find the data I collected for the standards I made. 

While you are making it difficult, I am trying to be helpful not confrontational.

Sorry you feel I am being difficult and confrontational.  Had I known asking a few questions would upset you,  I wouldn't have posted them.  Lesson learned.

[tim_]

I encountered the same issue of wanting to connect a 50 Ohm amplifier to the input of my oscilloscope (Rigol MSO5000).

I bought one of the "cheap plastic P57" through terminators. It turns out it really does not work that well up to 1 Ghz, see S11 measurement of the open terminator below.

What is a bit more concerning to me is that the 50 Ohm terminator does not really help to get the RF signal into the scope input. See below. One can also see that the gain selection of the channel has a clear impact.

Any ideas how to solve this? From the video above it seems that the easiest solution would be to add an attenuator? Of course that is not really preferrable.

[David Hess]

A feedthrough termination is not really suited to operation above 200 MHz where the input capacitance and stub length of the high impedance input become significant.  High impedance probes include high frequency compensation to handle this which is missing in a feedthrough termination.

At higher frequencies the change in input characteristics with input attenuator setting is insignificant because it is above the bandwidth of the oscilloscope.

[joeqsmith]

Experiments with a damaged part.

https://www.eevblog.com/forum/testgear/pasternack-pe6008-50-thru-term/msg947602/#msg947602

Joe,

I believe you were measuring the termination itself.   You did not measure it on the input of a scope.  I suspect if you try that again with the termination on a scope or meter input there well be very little difference for the various configurations.
...
Chris

Is four years considered a necropost?  Revisiting my modified terminators with a SPICE twist.