>From G3PLX: Alberto:
Thanks for your input! The peak in the centre of the spectrum plot you showed at http://sundry.i2phd.com/zeropeak.gif is certainly the small DC offset of the ADC's in the Delta 44. The Zero-IF software would remove this of course. It can be done automatically, it doesn't need a calibration process. Without this null, the DC offset might show as a faint tone, typically at 1700Hz, in the receiver audio. But you didn't hear it anyway on 40m, so there was enough band noise even to drown it. This is a promising result. But it still doesn't show if the new SDR1000 hardware has a low-enough oscillator radiation to be able to do this successfully. Sami's report of 'crud around DC' may say that it will not. Sami: Please could you try an experiment with this crud: First make sure that it is not generated inside the soundcard (see if it stays there with the audio input removed) or in the audio input cable groundloops (unplug the jack from the SDR1000 but touch the jack ground to the SDR100 chassis). If these tests are clear but there is still crud coming through the SDR1000, then see what happens when the antenna is removed and replaced with a 50 ohm termination. If the crud vanishes then it was surely caused by local oscillator radiation intermodulating with LF noise outside the receiver. Or maybe some others could try it. I would really like to know the answer. If it's not going to work with the new SDR1000 hardware then I will take my Zero-IF idea elsewhere. 73 Peter _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://mail.flex-radio.biz/pipermail/flexradio_flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
