On Thu, 14 Sep 2000 09:34:56 -0400 "Bruce R. Knox" <bknox@rfapps.com>
writes:
>
>Marv:
>
>You're selling yourself short on your carrier resolution, I think! If
the
>DDS is clocked from the 196.608 MHz, I get 0.04578 Hz per lsb (196.608e6
/
>(2^32)).
>
>But is this enough resolution for quality audio?
>
>Bruce R. Knox W8GN
>RF Applications, Inc.
>
Hi Bruce,
Your numbers are correct for the basic frequency resolution of the
system though, I am only planning to implement 1 Hz dial resolution.
However, the .075 Hz figure that you are comparing against from the FM
modulation description is also correct. Since there are only 16 bits of
audio resolution from the input A/D converter that is the maximum number
of steps (65536) available for direct digital FM generation. The .075
number is derived by dividing the deviation (5KHz in this example) by
resolution.
And this is just a mathematical limit. The limit in reality will be
slightly worse because the DDS is stepped at .046 Hz obviously not a
precise submultiple of .075 but, close enough for Amateur FM in any case
and certainly great for audio!
73,
Marv WC6W
*
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