It looks like the BB60C went from -133 to -112.5, and the DRT went from -128 to -121. This probably reflects how much out-of-band energy is hitting the amplifier, and that amplifier’s linearity. My guess is the DRT uses either a more linear amp, or a smaller passband.
One thing you could try, if you need a lower noise floor in this band, is to add a band pass filter. This should remove some out-of-band energy before it hits the amplifier and bring the noise floor down.
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