[Elecraft] K3: New Synth and frequency jump between connectors

[Jon Iza]

Folks,
after installing the new synth the Medium Wave stations which were
coming thru the antenna BNC are gone, and the Rx In BNC should be
used instead.
Is there a setting to decide the frequency edge where the signal path is
changed? Where can I find information on this setup? The synth manual and
the
FAQs do not help much.
Any hints appreciated.
jon, ea2sn