On Thu, Jul 10, 2008 at 10:39 PM, Chris Stankevitz <[EMAIL PROTECTED]> wrote:
> 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)? You *may* be seeing an artifact of the truncation of the ADC samples. In 8-bit mode, only the upper 8-bits of the post-CIC samples are sent. It's possible that your analog noise floor is at or below the new, higher LSB, and thus you get sinc-like sampling artifacts in the frequency domain. Run usrp_fft.py with all the same parameters but in scope mode with -S and see if the noise is just toggling the new LSB (+- 256). If increasing the gain makes an improvement, I'd bet this is what it is. In effect, you've increased the quantization noise floor by something like 48 dB ( 20*log10(256) ), and you're seeing the quantization noise spectrum. -- Johnathan Corgan Corgan Enterprises LLC http://corganenterprises.com/ _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
