Opps - ignore the following -I just realized in my mind I was going the wrong direction - I got twisted:
"If you were to add a signal source of 48 kHz, you would need to add a rational sampler in front of the WBFM block for a quadrature rate of 480 kHz"
If you add a 48 kHz signal instead of the null source, then it would match the input sampling rate for WBFM transmit block.
-- Cinaed
