[Elecraft] [K3] dual RX anomaly?

[David F. Reed]

I note an apparent anomaly with my K3 using dual RX...

say I tune to 24.953.43 with both main and sub; in the main RX I hear a 
tone (apparently a spurious signal, as no antenna is connected).  I do 
not hear it on the sub receiver; if I swap A/B it stays with the main.  
If I tune main or sub off slightly for a different pitch, it tracks main 
only.

Is it possible I have a slight spur that only affects the main RX?

Any thoughts?

FWIW, its not a big problem; when I connect an antenna, it is barely 
detectable through the noise.

Thoughts?

Thanks & 73 de Dave, W5SV