We will see how to make bit stream in GNU Radio.
Generally speaking, we can two different methods. One is using the Random noise block and the other is the using the Signal source block.
First, we make a flow diagram like a following picture.
You can download the grc file here.
(1) Random source block
First we are making 8 bit random signal (Maximum 256 = 2^8) and the output is defined as Byte.
The output signal will be unpacked data stream by Unpack K bits block. K should be 8 here.
and Char to Float block will convert the data stream from Byte to Float.
(2) Signal source block
This is very simple methods. We are just using the square wave. Please change the amplitude into 2 and offset into -1. Then you will see the 0 and 1 bit stream soon.
Here is the results of the grc file. Please do not miss the spectrum plot of each method. The spectrum of the random source looks flat over the frequency whereas the peak is observed in the middle frequency from the square wave source.