YT1NT> At 1 kHz filter input IM level was undetectable. The 6 kHz filter was then inserted into 1 kHz slot 3rd order IMD products for two 700 Hz signals are both outside 1 kHz BW and greatly influenced by skirt attenuation! Q24 might be a bigger problem then Q9 in Orion. 73 de Mario, S56A, N1YU