[Elecraft] [KAT500] need help understanding

[David Christ]

I recently added a KAT500 to my K3, P3, and KPA500.  I need some help understanding what I am hearing.  The KAT500 was installed as recommended by Elecraft.  The KPA500 is connected to the input, my hexagonal beam to antenna 1, my 40 meter dipole to antenna2, and nothing to antenna 3.

With the K3 tuned to about 7.075 MHz I observe the following:

If I disconnect my K3 from the KPA500 and either leave it unconnected or connect it to my dummy load the noise level shown on the P3 is about -140 db and no signals are seen or heard.

With the K3 connected to the KPA500 as normal connecting to antenna 2 (40 m dipole) the noise level is -110 db and signals are peaking at about -60.

Connected to antenna 1 (hexagonal  beam) the noise level is -120 and signals are peaking at -80.

When I switch to antenna 3 (no connection) noise is -140 db and signals are peaking at -100.  This is the surprise.  I did not expect to see such strong signals coming through with no antenna connected.  This is also true when the dummy antenna is connected to antenna 3.  What am I hearing here?  should I be hearing this?  I have some guesses but don't want to state them here yet in order to not bias people's minds.

Any help for this non-engineer?

David K0LUM