I'm trying to use a lock-in amplifier at a big distance from the signal source (laser communication between two buildings) and hence cannot use my reference input.
When I punch in the frequency of the transmitter (signal source), the lock-in signal output keeps oscillating.
Is this because: The frequency I punched in is not exact? or The signal phases are not synced? or The lock-in just cannot do this?
Any help would be much appreciated, Jim