[linrad] RE:Tuning RX2500

[Leif Asbrink <leif.asbrink@xxxxxxxxxxxxxxxxxxxx]

Hello Stan,


> My results were like yours. The final cal that I did a U 
> and then S was done in 128seg. All of my fials for the 2 
> channels were around .00001-3 for all freq. 
OK. Then you should have nice looking spectra :-)

> There is still a rise in the scope center at 48khz 
> of about 30db. Is this normal? 
This is noise at very low frequencies. I have one system
here that has a unmodified Delta44 in a Pentium MMX 266 MHz
computer. It runs 2 channels in 96 kHz bandwidth - but only 
when fft2 is disabled and the fft1 parameters are set for
"processing economy". On this computer the center spur
is 30 dB above noise. My "normal" computer, a PIV, 2.7GHz
with a modified Delta44 has the center spur at 15 dB only.
I think this is the unavoidable level of 1/F noise in the
A/D converter.

The center spur should not change if you disconnect the 
cable  to the Delta44.


73


Leif / SM5BSZ




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