Topband: Forbidden Frequency Part 2

[Charles Bibb]

Hi, All

Thanks for all the useful and informative answers to my recent 
post/question about the QRM on 1830khz.

Perhaps, though, I should have refined my original question somewhat.  I am 
well aware that all sorts of mixed BCI products litter the 160M band at 
10khz intervals, such frequencies determined by the 10khz spacing of AM BC 
stations in this country.  Often, at night, I also hear weaker carriers on 
1820khz and 1810khz.  But, what I was trying to address in my post was "why 
is 1830khz IN PARTICULAR so bad for so many different locations?"

I mean, sure, a unique combination of mixer products, beat notes, 
harmonics, etc. could conspire to make 1830khz a particularly "bad" 
frequency at MY QTH, but why then is it also such a bad frequency at 
everyone else's QTH? Surely the same set of circumstances that apply to my 
location do not repeat themselves for all US topbanders.

Still curious,

Charles - K5ZK