Worst longitudinal balance on HAM band?

I've noitced that intermittent noise is more often in HAM band (tones 400-483) than in other bands. I know this is band for amateur radio however as I know nobody in Poland (all the more in my town) use this band for amateur radio.

Furthermore, at one time (at this time I had disabled HAM band) I heared buzzing on AM radio and I had reconnection. I've noticed that most increase on QLN graph is in the tones 400-483. The first image is QLN without buzzing heared on AM radio. Secons image is QLN with this noise.

https://s22.postimg.cc/bxjdo95xd/qlnwithoutbuzzingon...
https://s22.postimg.cc/nzerifx69/qlnwithbuzzingonamr...

It seems that my circuit is the most susceptible to any wideband noise on these frequiences. I would expect that circuit is the most susceptible to noise on the end ones (483-511) because as I know the higher frequency the worse longitudinal balance. As I know crosstalk don't mask noise from other sources. However my circuit seems most susceptible to noise which isn't crosstalk on these tones where crosstalk is scarce.

Edited by konrado5 (Thu 23-Aug-18 16:27:16)