[Elecraft] KPA500 Shifting Bands without any change in K3 Frequency

[Andy Durbin]

"It can't be solved. The SSB and/or Data at that AF MARS frequency  is just
slightly below the band pass filter change over to the 5.3 bandpass filter
on the KPA500. That means that when you are on SSB, part of your rf envelope
crosses over to the 5.3 band filter which causes the amp to switch to the
higher bandpass (5.3) and when the rf at the frequency stops, the amp
switches back to the 3.5 bandpass.""

A similar problem was solved in the KAT500 by allowing the user to decide how much "importance" to assign the the RF detected frequency.  This was a welcome change from the Elecraft philosophy that "RF knows best and will be obeyed".

KPA500 doesn't have any published command that will prevent RF detected frequency from taking priority over a band or frequency command and it's not a problem when operating in the amateur bands the KPA500 was designed for.   

I see no reason the problem could not be solved for MARS users by a hardware mod that disables RF frequency detection.  There is obviously some risk that the amplifier could be damaged if normal band switching fails and RF detection has been defeated.  

There are several undocumented KPA500 serial commands that I became aware of as I developed my station controller software.  You could ask support if there is a command that allows the RF power required for band change to be user specified.

73,
Andy, k3wyc