[time-nuts] FE-5650A option 58 tuning word for 10 MHz output

[Clint Jay]

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 at 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 at 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 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
>>>>> 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 at cox.net> wrote:
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
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>>>>
>>>>
>>>>
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