[time-nuts] Re: World's most accurate PC clock!

Javier javier at nebulosa.org
Mon Jul 4 01:36:22 EDT 2005

Narrowband FM used in land mobile radio and amateur radio usually has 
25, 20 or 12.5 KHz channel spacing. 10.24MHz was mostly used in CB 
radios with a MC145106 or similar PLL IC, and with a double purpose: to 
obtain a 5KHz PLL reference and also as the 2nd local oscillator to 
convert 10.7MHz first IF to 460KHz second IF.

This reminds me another widely used crystal frequency for the list: 
12.8MHz is used in radio transceivers with 25 and 12.5KHz channel 
spacing, since 12.5KHz PLL reference is 12.8MHz / 1024 (and also another 
discrepances: 60.005 would be 60KHz with a 5Hz IF, no 5KHz, and also 
77.503 would be 77.5KHz with 3Hz IF, no 3KHz).


Javier, EA1CRB

W. D. wrote:

>At 19:09 7/3/2005, David Forbes, wrote:
>>Many older narrowband FM radio synthesizers using the MC145152 PLL 
>>chip use 10.240 MHz to give 10 KHz channel spacing with its 
>>binary-only R divider.
>Hmmm.  I thought FM had 200 Khz spacing, and AM had 10 Khz.
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