[Elecraft] KAT500 - does it earth antenna connections

[Andy Durbin]

"You don't need to manually choose an antenna on startup. It remembers what
was last used on each band (assuming you are using an Elecraft or Kenwood
rig with it). I think it will still remember the last used even in a dumb
situation without knowledge from the radio; it just needs the radio support
to have "per-band" memory."

No radio support is needed for antenna per-band memory.  All the KAT500 needs to know is the TX frequency.  It then decides which antenna to select based on "band" and the antenna preferences defined by the KAT500 PC Utility.

A weakness of this design is that, if only RF sensing is used for frequency determination, the KAT500 may fault due to a mismatched load before the appropriate antenna has been selected for the new band.

Antenna selection can be performed by serial command but, even though my controller is capable of that, I have seen no reason to replicate the antenna selection logic already built into the KAT500.   There is a caveat though -  the internal antenna selection logic doesn't work correctly when KAT500 is in BYP mode.  (The workaround for that defect is to never use BYP mode.  MAN mode with Byp active is electrically the same and antenna selection does work correctly in that configuration).

73,
Andy, k3wyc