Hi In most Rb’s (including the FE 56xx’s) the DDS is mixed with a fixed microwave frequency signal. The DDS only has to make up “part” of the total offset. You get roughly a three orders of magnitude improvement because of this. Rick has gone into all the gory details of why it gets done this way in talking about the 5071. It is the same thing on an Rb.
So, your basic math is correct about a normal DDS. In this case you are in the PPT rather than PPB range due to the multiplication. Bob > On Jan 9, 2017, at 10:40 AM, Scott Stobbe <scott.j.sto...@gmail.com> wrote: > > A 32-bit DDS synthesizing at 1/5 Fs, yields a tuning resolution of ~ 1 ppb. > So, I would imagine a slightly lower frequency is programmed into the DDS > and the c-field is trimmed to yield a higher precision. If the new > synthesized tone you wish to generate is an integer number of DDS codes you > could start by assuming the c-field is trimmed to be on frequency, but if > the new tone is a fractional number of 32-bit DDS codes you will have to > manually trim if you want higher precision. > > On Mon, Jan 9, 2017 at 4:48 AM, wb6bnq <wb6...@cox.net> wrote: > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
