[Drake] TR7 RF on audio

[KG4LRU at aol.com]

Hello to the group I have 7400 serial number TR7 with all filters NB7 and  
home made aux board, I hooked up shure 444 Mic in fact two of them. Both Mics or 
 getting RF on air results is slight raspiness Mic Gain is down so light only 
 comes on at faintly on Peaks as you move it up 9/10 position it gets worse. 
I  also can here it on the internal speaker and the external speaker.
 
Any clues were to start?  Both the PS7 and the rig our grounded.
 
Phil AI4dq