[Discuss-gnuradio] FFT --> IFFT

[Robert James]

When I take a signal, stream->vector-->FFT-->IFFT-->vector->stream,
I'd expect to get the original signal back.  Instead, I'm getting
something like the original signal, but following a very low frequency
carrier.

I thought this was due to the limits in vector size, but making this
very high (many times the sample size and signal freq) and the problem
continues,

What's weirdest is that a low pass filter or band pass filter on the
output don't seem to solve the problem!

What is my mistake?