I would agree with an unintentional radiator or cable leakage, as being the most likely candidates.
EPIRBs are not on MAD. Military ELTs make some noise, but not like what the OP was describing.
Generic radio geek, in southeast Michigan.
PSR-500, TM-742, TM-V71,TH-78, HTX-420, IC-2AT, IC-2E (clone), Pro-39, BC-235XLT, TK-290, XTS-5000