Whilst it may be good practice to have a band pass filter for each band I have found that it is not strictly necessary with the receiver module although I am only using an indoor aerial and have no high power transmitters nearby.
As far as the relays are concerned somewhere in the U3S documentation is the comment that two relays can be switched directly because of their low current consumption. This may not of course apply to other relays.
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Regards
Ian
G3VAJ
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