[BC] 9th FM harmonic causing interference

[mrfixit at min.midco.net]

> Has anyone one had an issue with 9th harmonic interference with   
> Cellular networks?

Yup, several years ago. 9th landed right on one of their channels,  
causing them to shut it down. I wasn't inclined to believe that 9x94  
would find it's way through PA, 2nd harmonic filter and antenna with  
any substantial energy, even if it were being generated. But it was  
and it did.

Cellphone tech and I visited transmitter one evening with his $30K SA,  
and sure enough, there it was. A *little* tweaking of grid tuning,  
neutralization broucht the level down by about 25db, if I'm  
remembering the facts correctly.

Had this transmitter been out of town, it would have never been  
noticed, but it was about a mile from cell site. Anyway, they got  
their channel back and I got a bit more educated.

Dave Dunsmoor