[RFI] Mysterious K3 Symptoms - RFI?

[Pete Smith N4ZR]

Operating in this morning's CWT, and saw a recurrence of strange 
RFI-like symptoms.  After transmitting, RX gain sometimes was severely 
reduced, but simply moving the K-3's AF gain a little would cause 
recovery to normal.  Sometimes, this was accompanied by a HI CURR 
warning on the K3's display, often occurring several seconds after 
switching back to receive.

My working theory has been RFI, but my station is pretty thoroughly 
fitted with toroids. Still, there seems to be a correlation between 
running my KPA-1500 at about 1100 watts and this set of symptoms, which 
I have not been able to trigger running 100 watts   To further confuse 
things, I just had another episode of this occurring *several minutes* 
after the last transmission.

One culprit I can think of is a 100-foot Ethernet cable between my 
station and my FIOS router.  I have bought a shielded replacement but 
have not yet installed it.  After reading some of the recent commentary 
about so-called "shielded" cables, I'm wondering if this is worth doing.

Any suggestions, either K-3-specific or more general, would be much 
appreciated.

-- 
73, Pete N4ZR