Stanford Research Systems SR844 User Manual page 14

1-4 Quick Start
6 Check the readings on the front panel
displays.
SR844 RF Lock-In Amplifier
At 1 MHz, a quarter wavelength is roughly 50
meters of BNC cable. Your BNC cable is probably
a lot shorter than this, so the signal input is close to
being in phase with the reference.
Press CH1 Display to select R [dBm]. The R[dBm]
display on CH1 should read +5.6 to +9.6 dBm.