Re: Keeping Tuned Freq in Center


Kriss Kliegle KA1GJU
 

   For a realistic display of **DC Offset, connect to one of my servers that has an SDR-iq… KA1GJU Super Stations #1,2,4 and KA1GJU @ PCARC if you know how to load a server into your definitions.
   Select the max bandwidth, 192 kHz and start it. Takes about 8 seconds, but once started tune to a quiet band where no signals are present and look at the signal in the center. Now re-center display with a right click on either side at a good distance from it and watch what happens. It’s always centered! SDRC will reduce it over time, but it remains. Disconnect from the radio and connect again at the minimum bandwidth choice and repeat. SDRC will do a good job of completely removing it. 

   If I operate the SDR-iq locally, it’s not as pronounced and SDRC removes it completely over time. Not all SDR’s behave this way, but this anomaly is only when I operate via my servers (99% of time), not when using the SDR-iq locally. I have brought this to Simon’s attention over a year ago, but I just live with it and listen to signals on either side on center just fine.


** The DC offset is the difference between the ADC's "middle" voltage and the average voltage present at the ADC's input. The analog circuitry in the SDR will contain biasing circuitry designed to minimize the DC offset.

73 Kriss KA1GJU 


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