[1000mp] MkV and strong signals

[Jim Martin]

Happy New Year everyone!
I am having severe problems with the MkV  and MMTTY on a busy band.  When a
strong signal starts up many KC/s away the trace on the display drops almost
to zero and I have problems decoding the station I am listening to.  All I
can hear is this off frequency station, everything else is obliterated! The
IC746 works much better so I assume I have messed up some settings.  I have
tried IPO on/off and AGC off, both help but not enough.
The MkV filters fitted are as follows
8.2 MHz   250Hz  and  2.0KHz  both Yaesu
455KHz   250 Hz(Yaesu) , 400Hz (Inrad), 1.8Khz (Inrad)
400Hz Inrad second RX
I am using FSK with the mode set to RTTY.
SSB and CW operation seems fine ( but maybe it should be better?)  How can I
check for myself how the rig is performing?
Any comments on menu set-up and filter selection would be appreciated.
Thanks
Jim  MM0BQI