[Elecraft] RF feedback?

[K2QI]

I've noticed that I get some sort of RF feedback spike when using the SB-220
and keying up in sideband mode.  It's enough to trip my SWR alarm in my
wattmeter.  What is odd is that it doesn't happen on keydown CW.  The
problem also gets worse when keying up in sideband mode with mic gain turned
down lower.  If I raise mic gaini, the RF feedback isn't as bad and the
alarm doesn't trip as often.  Thoughts?

James K2QI