[time-nuts] FE-5650A option 58 tuning word for 10 MHz output
cjaysharp at gmail.com
Mon Jan 9 14:20:09 EST 2017
Option 58 in a FE Rb is an additional sub board which has nothing to do
with the physics package control loop.
In an option 58 Rb there are two DDS chips.
On 9 January 2017 at 17:48, Scott Stobbe <scott.j.stobbe at gmail.com> wrote:
> It very well could be. Based on Marks comments, it sounds like the DDS tone
> after being squared up is directly driving a 23-bit counter for the 1 PPS
> On Mon, Jan 9, 2017 at 12:17 PM, Bob kb8tq <kb8tq at n1k.org> 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
> > the
> > PPT rather than PPB range due to the multiplication.
> > Bob
> > > On Jan 9, 2017, at 10:40 AM, Scott Stobbe <scott.j.stobbe at 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
> > > 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
> > > the new tone is a fractional number of 32-bit DDS codes you will have
> > > manually trim if you want higher precision.
> > >
> > > On Mon, Jan 9, 2017 at 4:48 AM, wb6bnq <wb6bnq at cox.net> wrote:
> > >
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