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" <wb6bnq@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.stobbe@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 <wb6bnq@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/mailman/listinfo/time-nuts >and follow the instructions there. > > >

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" <wb6bnq@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" <wb6bnq@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.stobbe@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 <wb6bnq@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. >