Log detector Vout accuracy: CW vs 8PSK modulated carrier, same Pin (-45 dBm)

I'm having issues with measuring RF receive power using a log detector, Pin vs Vout.  I'm using a sine wave (CW) as Pin and to characterize slope and y-intercept.  After initial measurements, increasing/decreasing Pin provides accurate Vout measurements converted to dBm.  I'm using an Arduino microcontroller to convert A/D.  However, when I measure a carrier signal (Pin) from a satellite signal, my Vout is not accurate and does not change.  I'm blocking an antenna and measuring a 9dB drop on a spectrum analyzer, but the power detector does not measure the drop in this setup.  I'm uncertain why the benchtop test and satellite carrier produce different results.  Both power levels are the same (-45 dBm), which is significantly above sensitivity for the detector.  Does a modulated carrier (8PSK) have different results than CW?   

I've verified proper filtering and the filtered signal does not have other spurious signals across the spectrum (1Hz up to 1GHz).  Do others recommend a specific detector to simply measure receive RF signal power or RSSI?

 

 

AD8310-879649