AnsweredAssumed Answered

8722ES - Long cables and electrical delay.

Question asked by gatekeepr69 on Nov 8, 2013
Latest reply on Nov 16, 2013 by gatekeepr69
We routinely perform antenna measurements with total cable lengths of over 40' and path separation up to 3meters , we currently have an 8510C, 8753D, Lightning, Scorpion, and just purchased a used 8722ES,  it was sold to us with a valid calibration.

In a preset condition if we hook up a 20' cable to the 8722ES the S21 falls on its face by a factor of 40dB from 2.5G all the way to 40G until we either reduce the sweep time to over 1.3 seconds or switch it to step sweep mode. 

I do understand that as you increase the test port electrical delay the frequency shift between the R channel and Test port channel will increase and the error will be consistent with the roll off of the IF filter. but we have never seen dropout of 40dB under preset conditions. With all of our other analyzers the error is usually within .5 to 5dB MAX with default sweep speeds. 

I have already viewed the application notes below regarding electrical delays. while the behavior matches that of our other VNA's , not the 8722ES   -  Pg. 4

My big question is... is there anyone here with an 8722ES who can verify if this behavior is normal or not... 

I attached a picture for reference. 

James Martin 

James Martin
Diamond Engineering