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M17-Project / rru-rf-hw

Remote Radio Unit - RF board
https://m17project.org
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RF lowpass filter - proposed values #16

Open sp5wwp opened 1 month ago

sp5wwp commented 1 month ago

L1, L2 as described in the schematic: 0.8 mm silver plated copper wire 3 turns 3.2 mm inner diameter ~4 mm length Resulting inductance should be around 24 nH.

C17, C18 plus PCB trace stray capacitance (3.8 pF measured): should add up to 6.8 pF. Proposed values: 1.5 + 1.5 pF. C20, C21 plus PCB trace stray capacitance (3.3 pF measured): should add up to 13 pF. Proposed values: 8.2 + 1.5 pF. C24, C25 plus PCB trace stray capacitance (4 pF measured): should add up to 6.8 pF. Proposed value: 2.7 pF.

PNs: 12062A2R7CAT2A - MLCC, 200V 2.7pF C0G 1206 0.25pF tol. 12067A1R5CAT2A - MLCC, 500V 1.5pF C0G 1206 0.25pF tol. 12067A8R2BAT2A - MLCC, 500V 8.2pF C0G 1206 0.1pF tol.

sp5wwp commented 1 month ago

If the values are OK, I'll update the schematic accordingly.