Could you have used a single point frequency measurement n the VNA? I know the 8510 will do that.
But I am sure the experience was educational - thanks for the education - it would have taken me a bit of time to catch on to that.
Cheers!
Bruce
Quoting "Harke Smits via groups.io" <yrrah@...>:
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Hello,
There is one more issue to consider. Long lines give delays. Once I wanted to measure the loss of a coaxial cable on a vna. Was an interesting experience: no response. Until I realized the receiver had already traveled higher up in frequency at the time the response was back. You need to consider a delay in between frequency steps, long enough so as to give the receiver time to read the response. This is a documented feature (of course).
Good luck,
Harke, PA0HRK
On 26/05/2022 20:09, Tom Lee wrote:
Hi Karin,
"Upper limit" is not as hard a cliff as your question presupposes. Whether or not a given length of cable is too much depends on your acceptance criteria. What are you trying to measure, and to what accuracy do you need to measure it?
When you add cable, you get loss, so that loss subtracts directly from your dynamic range. For example, if you are making meaurements at a gigahertz or so, with RG-213 you can expect to lose about 10dB in each direction, roughly speaking. If you aren't trying to measure small deviations from an exquisitely well-matched load, you'll be fine. If you're trying to resolve small changes in the vicinity of a -60dB S11 null, then you may find the measurement challenging.
The other factor to consider with a long length of cable is that it isn't rigid, so stability of your measurement can be affected. And if you are doing a lengthy set of measurements, temperature effects can come into play as well. Whether these are "don't cares" or showstoppers depends on what you can tolerate. If you can tolerate large error bars, your measurement problems become much less severe. If you're trying to make publication-quality measurements, you may find that difficult.
Good luck!
--Cheers,
Tom
--
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
On 5/26/2022 09:45, Karin Johnson wrote:
Hello Group:
I have an 8753C and am wondering what the upper limit on cable length would be if I place the cal standards at the end of a cable to do remote measurement of S11.?? In other words I am using SOL, with the cal standards placed at the end of a 100 foot length of RG-213.? Theoretically placing the measurement plane at the end of the cable.? I have already done this and the results seem to be accurate relative to an actual measurement at the that physical place.
I hope I have explained this issue sufficiently.
Regards,
Karin Johnson
BTW: I have had an account on the Keysight forums in the past and have recently tried to login to that site, but It won't let me.? Possibly password have changed, and I cannot create a new account.? I have posted with Keysight support and hope they return the email.
