Re: BPF too good? #filter


KEN G4APB
 

Your results will depend on what other losses you have taken out in the CAL. The 4 pole non-50 ohm connections to the filter should NOT be calibrated out if you want a true 'in circuit' reading as they appear in the actual U3S. I found if you measure filters in-situ, especially if you start using the switched relay board with multiple filters (BPFs), the filter responses soon become misshapen and losses increase rapidly. I measure some 5-6dB in circuit losses in my mutiband U3S Rx.
Having said that, your tune and test up method looks good.

73 Ken G4APB

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