[Discuss-gnuradio] 8 bit samples have an odd spectrum

[Chris Stankevitz]

Hello,

a) Here is a screenshot of 16 bit noise @ 12 MHz:
http://img224.imageshack.us/img224/8981/16bitsb0.png

b) Here is a screenshot of the same noise with 8 bit samples:
http://img60.imageshack.us/img60/5852/8bitqg7.png

c) 8 bit noise, tuned to 12.5 MHz
http://img224.imageshack.us/img224/1596/8bitoffsetua5.png

My questions:

1. Why does b) show a lobe while a) does not?
2. Why do b) and c) show lobes at the same pixels (vs shifted .5 MHz)?

The spectrum should be entirely noise.  The signal is from an antenna 
plugged into a front end that brings 1.57542GHz (GPS L1) to 12MHz.

Thank you,

Chris