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kalee20 · 20th Dec 2007, 4:05 pm

It's because 198kHz is a multiple of 9kHz, and 200kHz isn't! To cram as many stations as possible in the AM bands, they are as close together as possible in frequency terms, and 9kHz has been internationally agreed as the minimum spacing (this also imposes a limit of very little programme content above 4.5kHz to avoid spilling over into an adjacent channel).

It also makes things easier for synthesized tuning in receivers - you have a master clock at 9kHz and just use multiples of this (with an appropriate intermediate frequency also a multiple of 9kHz, e.g. 468kHz).

I'm also looking forward to the answer as to when it was changed - I do agree, 200kHz is nice... as is 1500m...

20th Dec 2007, 4:05 pm	#7
kalee20 Dekatron Join Date: Feb 2007 Location: Lynton, N. Devon, UK. Posts: 7,087	Re: Frequency Standards It's because 198kHz is a multiple of 9kHz, and 200kHz isn't! To cram as many stations as possible in the AM bands, they are as close together as possible in frequency terms, and 9kHz has been internationally agreed as the minimum spacing (this also imposes a limit of very little programme content above 4.5kHz to avoid spilling over into an adjacent channel). It also makes things easier for synthesized tuning in receivers - you have a master clock at 9kHz and just use multiples of this (with an appropriate intermediate frequency also a multiple of 9kHz, e.g. 468kHz). I'm also looking forward to the answer as to when it was changed - I do agree, 200kHz is nice... as is 1500m...