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

[Gerhard Hoffmann]

Hi, Abdul!

Am 21.01.20 um 19:10 schrieb Prologix:
> Prologix controllers pass data as is from the instrument to PC. It does not add any termination characters.

But then there is the ++eot command just to set up this.

> ++eos command controls how termination is handled for data going the other way -- from PC to instrument.
> Please consult instrument manual about how it terminates output.
I also could not see what the timeout does. When I try to read a 
character and
none is available it still hangs forever, even with the timeout set to 2 
seconds.

We should take that offline probably.



In the meantime, the LAN connection to the FFT analyzer works again.
Ansi C requires some re-synchronisation when switching the direction of 
the data
flow in a TCP/IP connection or you may get old messages a second time.
An otherwise empty fseek() is enough, per side effect.
A year ago, the connection to the analyzer was solid, then it would hang 
now & then
and in retrospect, since I have the current V5 Linux kernel it is unusable.
The fseek() has healed that.

There is still the minor? problem, that from low to high frequencies, 
many new decades
start with elevated noise, but I correct for the increased noise 
bandwidth. Maybe discrete
spurii are then over-represented? I'm unsure how to handle that. When I 
add a carrier
from a signal generator for CAL reasons, that carrier level should not 
be changed by noise BW
correction, assuming that all of the carrier power hits the same bin?

The amplitude of the carrier in the picture has been corrected for 5 
decades = -50 dB,
and that's obviously wrong, the 3325B is not that bad. When I do a 
narrowband sweep, it
looks OK on the FFT analyzer screen.

Even when I go through the spectrum and decide that this or that is a 
carrier and it should
not be downscaled, how do I handle its sidebands? There is no pure black 
and white.

Cheers, Gerhard


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