The problem is that, adding more boards, the overall impedance "seen" by the transmitting board falls down: each board is a "resistor" that adds in parallel to the bus. The overall impedance seen by the transmitter is a set of parallel impedances made by the power supply and the boards. Increasing the inductors size will reduce the problem because it increases the impedance introduced by each board in the bus.
If you run the simulation you can see that so big inductors introduces a lot of "artifacts" at the beginning and at the end of the modulated signal. A 50Hz superimposed on the voltage bus is catastrophic :-(
With a commercial three state buffer we can manage up to 30mAmps... so the budget is very limited.
I'm start to thinking that the overall proposed solution is not affordable due to costs and/or technical problems.I have to think about.
In your previous schematic, using 220uH coils and 1uF capacitor you were in the rage 10-86 KHz (omega0, omega1) so the 50 Hz should be out of these problem. Maybe you are finding this using new values?
If you have time, please try the numbers that I've proposed.
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