I need to measure two Type-N(m) devices with my 8753E. One has a 100ohm impedance and the other has a 150ohm impedance. I wish to measure the impedance and the reactance of both devices at frequencies below 200MHz. After I complete the measurement, how do I determine the accuracy or the uncertainty of the measurement??? I know that I should probably be using an Impedance Analyzer, but I do not have one available. Is the 8753E able to deliver good results for this measurement?? I wanted to have the end result be within 1% of the actual impedance value.

Thanks...

Thanks...

Please describe your device in more detail for a more detailed answer.

In short, just take the directivity, source match and tracking and computer the error on the gamma measurement, and then convert that error to impedance:

Roughly speaking; Error = D+Tr*gamma+SM*gamma^2; Suppose directivity is -40 dB (0.01); tracking is 0.1 dB; Tr= 1-(10^(.1/20))=.011; Source match = -40 (0.01)

for 100 ohms, gamma = .33 (actually, .33 gamma is 99.26 ohms) ; error = 0.01+0.011*.33+0.01*(.33)^2=0.0147 (mostly directivity). Thus, gamma error results in gamma range of .3153 to .3447; convert to Z: 50*(1+gamma)/(1-gamma): 96 to 102.6; so the error is about 3.26 ohms.

Note, directivity of -40 dB is an error of about 1 ohms at 50 ohms! Easy, eh.

It is actually three devices. All three have type-N connectors on them. They are labeled 50ohm, 100ohms and 150ohms. They are used to test handheld items similar to Site-Masters. I guess that they are similar to offset terminations? Except, offset terminations that I am familiar with normally have a nominal return loss value or VSWR value with a specific tolerance. The offset is then connected to the Site Master and the Site Master will display the value of the offset in dB or SWR as a verification of the operation of the Site Master.

These items were mfg’ed for us to test items similar to the Site Master. Our items will not read return loss or VSWR….they will only display the Impedance and reactance. When we asked about the specification of the three devices that were made, the manufacture just noted that they tested the units with an 8753E and gave the “As-read” readings from the Smith Chart. So we would like to verify the three devices with our 8753E…but It does us no good if we do not know how accurate our results are.