Dear All,
I am working on a test system that measures the frequency of 16.367 MHz TCXO oscillator and verifies within the range of +/- 33 Hz.
When I put the DUT Module onto the test fixture, the test pin probes the output of TCXO and measures the frequency with reference to ground.
Immediately after the test pin to TCXO, on its way to frequency counter E1420B (agilent), one adjustable inductor coil (max: 0.12 uH) is added in parallel with capacitor 266 pF in between.
I wonder what is the use of LC circuit in frequency measurement.
From practical experiments, I found that adjusting the inductance affected the stability of the measured frequency value in E1420B.
Could anybody please explain to me the reason why such kind of LC circuits are added in frequency measurement?
Why can't I just directly connect to the Frequency Counter?
They call such circuit "Sniffers"
Regards