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HP 4396B network analyzer

Question asked by twomilimeter on Dec 24, 2009
Latest reply on Dec 29, 2009 by twomilimeter

I am just beginning to use a network analyzer.
The model is HP 4396B network/spectrum analyzer.
I started by trying to measure the input power at the R and B channel by changing the RF power source.
The RF source, R and B channel are connected to a two way power splitter. The setup is shown below.

I set the "meas" button to B to measure the power on the B channel and "meas" to R to measure the input power to the R channel.
The relationship of the output power from the RF source with the measured input power to the B channel are shown below.

I am a little confuse here. Why does the measured power at the R or B channel is larger than the RF power source?
For e.g., when the RF power source was set to -10dBm, I am measuring -15dB. Is -15dB the input power at the R or B channel or I have mistakenly understand the unit?

Secondly, I try to measure the response of a RC circuit with 50 ohm input and output terminated with R = 100ohm and C = 10pF. The 3dB roll off should be ~1.5MHz.
I set the "meas" channel to "B/R" and later to "B".
The setup, measured gain and phase are as shown below.
RC Setup

Gain with "meas" set to "B"

Phase with "meas" set to "B"

Why does the phase always change from -180 to 180? What does the phase indicate when the "meas" is set to "B/R" and "B" only?

Kindly advise.

Thank you very much.