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:
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