[time-nuts] was: Odd-order multi Now: fft analyzer woes

[Gerhard Hoffmann]

Yes, that spill-over to neighbor bins is a known thing; when I wrote 
software

for mixed signal wafer testers we sometimes used no windows at all and

instead made sure that all frequencies involved were proper submultiples

of the sample rate. In my current situation I'm limited to what the 89441A

has to offer, and that is not too much. IIRC the manual proposes flat top

for sines and Hanning for noise. While there is no such thing as a Hanning

window. That Guy was Justus von Hann, from Austria.


Carriers are also not of prime interest at the moment; I'm more focused

on the noise itself. Maybe 1/f of oscillator transistors or the noise of

GaN fets in a pV/rtHz chopper amplifier where the GaN have some appeal

for low charge injection. When I used my URV-35 with the Z51 thermal

head to measure the noise, the result would be dominated by the 1/f,

even though the Z51 collects everything to 18 GHz.

And when I measure phase noise, the carrier has already been

carefully and lovingly removed.


With all that TCP/IP and GPIB programming and C library feature

flavor macros I feel already quite deep in the wrong rabbit hole.


My test carrier is not off by milliBels but by 50 dB and correcting that

won't probably work without some lying where the carrier hits the noise 
floor.


Cheers,

Gerhard, DK4XP


Am 24.01.20 um 01:59 schrieb jimlux:
> On 1/23/20 4:20 PM, Magnus Danielson wrote:
>
.....