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All,

when I first looked on the schemtaic of the ?BITX I felt a bit sceptical about the way how the low pass filters are switched. Only one relay for input and output of the lpf? What about the crosstalk within the relay?

So my scepticism comes true.

Personally I always would use two relays one of the input and one for the output, even short circuiting the non switched filter. And remember: every relay contact has a few pF of capacitance. This will add to the existing filter cap.

The remedy would be an extra lpf board.

And in addition please also use bpf?s in the transmit and receive path in order not to overdrive the first stages / mixer.

Recently i read an interesting blog from an austrian ham: he destroyed xtal-filters when his high performance (high IP3) receiver was connected to a high performing antenna! Out of ham band stations were overdriving the stages--- please remind that xtal filters do not want "high power signals" in the range >0 dBm even at stop band!!!