[amsat-bb] AO 91 Rumbling Noise

[Bernie and Cheryl]

Dear Folks:

Forgive me if someone has already discussed this, but I noticed a 
"rumbling" noise in the background during this morning's AO 91 pass.  
What is that?  It almost sounds like a train is passing by.  It was not 
dependent on someone transmitting as it was present even while there was 
no one speaking.  But, it faded away as soon as the pass was over at my QTH.

73 de Bernie, KF0QS