[Elecraft] Hunting K3 subRX gremlins

[Gary Hinson]

Dear Elecrafties,

Does anyone have any idea why my subRX might be intermittent on 40m?  

Sometimes, for no obvious reason, all I get is hiss in my right ear, no
sigs.  As far as I have noticed so far, it only happens on 40m.  I don't
think it's the subRX attentuator/preamp, antenna, RF gain or filter
settings.  On Thursday when I first noticed it, I re-calibrated the subRX
synth (among other things) and the gremlins went back into hiding, but not
for long: this afternoon, the gremlins returned.  Earlier this evening I
tried various things such as power-cycling the rig, meddling with the subRX
settings, changing bands and then returning to 40, but still just hiss.
Tonight after dinner, I returned to the rig (still powered up) and the
gremlins have crept back into hiding: the subRX is working again on 40 but I
fear they're just teasing me now.

Any clues about where to hunt first after "... 98, 99, 100 coming ready or
not!"?

73
Gary  ZL2iFB

PS  Also, is the subRX meant to work cross-band with the current/latest
firmware?  CONFIG: VFO IND won't budge from "no" (it just says "UNAVAIL"
when I try to change it).