karl gruber wrote:
The main difference between a KX-155 and a KX-155A is that the later was
designed and built after GPS was in use. The "A" models do not interfere
with GPS.

ALL the older radios, straight 155, 170 series will interfere with GPS. That
is the reason one has to test certain frequencies in an IFR GPS
installation. One can be sure that if there is a straight 155,or 170 and
older radio in your airplane, you will not be able to pass that test.

I'm sure Karl meant to say "...you will possibly not be able to pass that test."