E4440A options 115,123,105,233,BAB. S/N SG46182507 w/ N5532A option 526 S/N N10149. Monitoring output of a 8642A @ 1.5GHz, 100kHz FM, 0dBm, modulation frequency 300Hz. I selected HP 50Hz and LP 3kHz and + peak FM on PSA/MMR. The analyzer measures 39---kHz. I take off the 50Hz HP filter and now this thing displays 99.9--kHz. I need to use the LP and HP filters to minimize residuals to test a mod. analyzer. Is this thing broke or what?