[time-nuts] FE-5650A option 58 tuning word for 10 MHz output
cjaysharp at gmail.com
Tue Jan 10 02:46:57 EST 2017
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.
> Bob kb8tq wrote:
>> 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
>> 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.
>>> On Jan 9, 2017, at 10:40 AM, Scott Stobbe <scott.j.stobbe at gmail.com>
>>> A 32-bit DDS synthesizing at 1/5 Fs, yields a tuning resolution of ~ 1
>>> 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
>>> 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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