Here is the idea how we upgrade the demodulation boards.
Basically we go ahead with two steps as depicted in the cartoon diagram below.
Once we finish the first step of upgrade, the board will be ready to install although the circuit won't be awesome in terms of noise performance.
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First of all we will replace the home-made 90 degree splitter (see this entry) by a commercial splitter, PSCQ-2-51-W+ from Mini circuit. This is the step 1 basically.
At this point the boards will be ready to use in principle. I asked Steve to get three 90 degree splitters so that we can have at least three demodulators for the dual-recycled Michelson locking.
If they work very fine we will buy some more 90 degree splitters for full locking.
While we try to lock the dual-recycled Michelson once we will get a Cougar amplifier, remove all ERA-5s and install it such that we don't have to gain up and down in the circuit. This is the last step.