[Elecraft] [P3] Listening in the AM Band

[Al Lorona]

Here's one I bet you guys haven't run into yet. I was tuned to a local AM station on 710 kHz which was showing up as a -75 dBm carrier on the P3.
 
Every 8 seconds a relay would quickly cycle off and on (or on and off, I don't know which) inside the P3 which would reduce the displayed amplitude of the signal by a few dB while it was in the transient position. This was perfectly repeatable. 
 
However, inserting a 10 dB pad in the antenna path to reduce the signal amplitude to below about -80 dBm stopped the relay from cycling. Is this some kind of protection circuit?
 
Al  W6LX