Howling/Ringing in OMNI VI 500Hz Filter

[n1jm@dreamscape.com]

H. L. Serra wrote:
> 
> Thought I'd toss this one out to the OMNI VI users: I have one of the
> early OMNI VIs, and it has always displayed filter "ringing" ONLY in the
> 500Hz filter position in CW mode. None of the other filters do this. Also, in
> 500Hz, when I use the PBT control, a continous "howling" occurs which
> changes slightly in pitch as the PBT is tuned. Any similar experiences or
> fixes?
> 73, Larry N6AZELarry: How did you make out with the product detector mod from England? 
My Omni is a little over 3 years old and I don't think I am getting what 
you describe.
John N1JM