Re: RTL2832U FIR filter

2012/7/14 Michael Karcher osmosdr@mkarcher.dialup.fu-berlin.de:

I furthermore found out that this is not the only filtering going on in the RTL2832 chip in SDR mode. There seems to be a second anti-aliasing filter before the DAC, making signals disappear that are at frequencies above 0.7 times the sample rate (in the baseband), even if the programmable FIR filter lets them pass.

That's probably an effect of the E4000 output filter. You can see the filter bandwidth being set in the tuner initalization code.