Hi Floyd,
My neighbor has an electric fence which gives regular pops when listening to 40M. The NB reduces those quite a bit, but not completely. Now that you mention it, I might try replacing the diodes anyway, and see if it works any better.
The VFO on mine drifts quite a bit, even after nearly half an hour. How stable is yours?
Cheers,
Peter - VK2AN
Peter E