On 29 Apr 2013, at 22:51, Richard O'Neill wrote: > On 4/29/2013 5:37 PM, Karl W4KRL wrote: >> I think it is more correctly a notch filter. > > Yep, I use one as a 'wave trap' in my crystal set. > > Richard Me too. But what is a "notch" filter if not a "band stop" filter? Is there a distinction? Phil M1GWZ