[time-nuts] TI Counter Noise Floor/Resolution

Brian Kirby kirbybq at bellsouth.net
Thu Jul 28 16:06:50 EDT 2005

Why we are talking about resolution and noise floor, I am looking for a 
merit figure to say the data I have measured, is valid.

As an example, when I worked in satellite communications, we had a 
measurement called C/kt. This is a carrier to noise measurement, 
normalized back to a 1 hertz bandwidth. When we made these measurements 
with a spectrum analyzer, we had to account for the measurement 
bandwidth of the instrument, the detector used (factors for sine wave 
response vs. gaussian noise), etc. Basically if the reading was 6 db 
above the noise floor, then we could believe the measurement.

In my case, were I have baselined the HP53131A noise floor, I know my 
readings have to be above this floor, to be valid.

My question is how much should our readings be above the noise floor to 
be considered valid, and what units/formulas should we use ? Can we 
convert Allan variances to a decibel reading, and use similar techniques 
as I described?

Brian – N4FMN


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