Oh that's interesting, I've not seen the non DDS version of the 5680 yet. The frequency division for output in the non option 58 ones I've had hands on was definitely done in a CPLD chip, the DDS was "for internal use only" as far as I could tell.
On 10 Jan 2017 09:07, "wb6bnq" <wb6...@cox.net> wrote: > Hi Clint, > > Actually there are two versions of the 5680. The older version is exactly > like the 5650 option 58 composition. The newer version has the DDS as part > of the signal generation for the physics package. And it appears that they > may be using an FPGA programmed as a divider to provide the output > frequency. > > Bill....WB6BNQ > > > Clint Jay wrote: > > Yes, in the 5650 there's only DDS on opt 58, in the 5680 there is one in >> the main loop too, my bad for not being precise/muddled. >> >> On 10 Jan 2017 01:43, "wb6bnq" <wb6...@cox.net> wrote: >> >> >> >>> HI Bob & Clint, >>> >>> If you look at the second message of this thread, I attached the manual >>> that applies to Option 58. Look at PDF page # 16 and you will see that >>> there is no DDS in the physics package. The DDS is only used down stream >>> in some variations of the product such as the Option 58 being discussed. >>> >>> Bill....WB6BNQ >>> >>> Bob kb8tq wrote: >>> >>> 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/m >>>> ailman/listinfo/time-nuts >>>> and follow the instructions there. >>>> >>>> >>>> >>>> >>>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to https://www.febo.com/cgi-bin/m >>> ailman/listinfo/time-nuts >>> and follow the instructions there. >>> >>> >>> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/m >> ailman/listinfo/time-nuts >> and follow the instructions there. >> >> >> > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/m > ailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ 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.
