If I use the 80.0e6 instead of 486111.111, my channel power matches Spike for a CW type signal, but not a 20MHZ White Noise signal. Below are the values from Spike and my computed channel power using both values.
Spike My ChPwr (486) My ChPwr (80.0e6)
CW Signal -51.62 -52.7 -51.6
20MHZ White Noise -51.5 -55.0 -53.9