>>> For consistent results, you should stick with commonly used samples

>>> rates like 1M 1.024M 1.2M 2M 2.048M 2.4M Avoid things lower than 1M

>>> and avoid weird, not-often used, values.

Thank you Sylvain.

I thought 900 ksps was one of the standard rates in the RTL2832 chip, so that's why I used it, to keep cpu usage low because my application must work in a Intel Atom N270, the smallest one.

In fact I used many times 900ksps with GNURadio 3.6.x without any problem at all.

I'll use 1Msps for now.