[time-nuts] Question about KE5FX Tools -> PhaseNoise Tool
sr75pro at free.fr
Mon Oct 17 03:49:42 EDT 2011
Le 16/10/2011 18:20, Peter Krengel a ecrit :
As expected I got a horizontal line at -127dBm from 10-100Hz.
Unexpectedly level changed from 100-200Hz as a falling curve down to
-132dBm and went on horizontaly further at this level to 1kHz.
During the measurement I observed the instrument and saw that it
RBW 10Hz to 100Hz so that I guess thats the reason for the
between 100 and 200Hz f-offset. So the observed effect seems to be a
of the Anritsu instrument.
Similar happened between 1-10kHz and so on.
My question: How can I adjust that offset to get a smooth measuring
This is known to happen. Here's a link  to an Agilent FAQ regarding
the HP70000 series modular spectrum analyzers. It's an interesting case
because you get different behavior (noise increases or decreases)
depending of the combination of RF/IF sections you choose.
Time to review the Friis formula .
 Agilent FAQ : Why does the noise floor rise when changing RBW
from 300 kHz to 100 kHz in a 71210C Spectrum Analyzer?
If the link is broken, go to agilent.com, copy and paste "DANL
comparison" with the quotes in the search box, select "Electronic Test
and Measurement" and the site will offer the FAQ as "71210C: DANL
comparison to 71200C".
 Wikipedia: Friis formulas for noise
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