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Question re. "SDR Data File Decimator"

Joachim Rabe
 

Hi, list,

please bear with me if this has been discussed or answered before but though I have used the search function on the group-website I wasn't able to find something matching my problem.

I use two PERSEUS-receivers on two different PCs to make overnight recordings which I later split in smaller chunks using "SDR Data File Decimator" in order to be able to analyze them quicker by means of the "SDR Data File Analyser".

What I realized is, that on only one machine, the results are off-frequency.
Let's assume I have a PERSEUS-recording with a BW of 1.000 kHz which I already split into 4 equal parts.
When I perform an analysis on 350 kHz the carrier of NDB FU-350 is not displayed spot on 350 kHz but rather ca. 250 Hz higher. (See attachment ATT-2)

It's even stranger that this difference of ca. 250 Hz can already be observed when loading a PERSEUS-recording to the Data File Decimator (see attachment ATT-1).
The bandwidth of the recording is not the full 1000 kHz as is should be but rather only 999 kHz.
Therefore the four parts are not 250000 Hz wide but rather 249750 Hz only - however, both Perseus are set up the same.

Also if I load a full recording into "SDR Data File Analyser" without prior splitting I realize, that signals are slightly off-frequency.
Taking the same example, the carrier of NDB FU-350 is shown 6 Hz lower than it should be, although the PERSEUS has been calibrated carefully.

This odd behavior is only happening on one PC. Results on the other machine are as expected.
The only difference between those two machines is, that the one working OK has an Intel I7 processor and the one not working OK has an Intel Xeon processor.

Does anyone have an explanation what's going on here?
Am I doing something wrong or am I missing something?

Thanks very much in advance.

73s

Joachim Rabe