[1000mp] Apparent receiver overload on 80M

[John Becker]

Only on 80M, my S-meter runs S5-S7 all the time just on band noise. The 
NB has no effect, and it doesn't sound like power line noise. If I press 
the IPO switch, the S-meter goes to zero unless there is a signal 
present. During the day, switching in 6dB of attenuation has the same 
effect. At night, 6dB isn't always enough. These symptoms indicate to me 
that something is overloading the receiver, but there is nothing obvious 
to cause this. Any ideas as to what it could be, or is this normal for 
the receiver on 80M with an inverted Vee?

73,

John, K9MM