[time-nuts] FE-5680A performance - 1 PPS output issue

bg at lysator.liu.se bg at lysator.liu.se
Thu Jan 5 22:57:45 UTC 2012


Chris,

> On Thu, Jan 5, 2012 at 1:48 PM, <bg at lysator.liu.se> wrote:
>
>> Hi Chris,
>>
>> > The documentation I have says pin 6 is "N/C" but it looks like there
>> is a
>> > way to extract a usable PPS but I think I'm going to need and LC
>> filter,
>> > some op amps and a one-shot and a TTL level driver.   My guess is that
>> pin
>> > 6 is either some kind of engineering test/diagnostic signal not
>> intended
>> > to use used or the signal is an accident.
>>
>> I have two of the older generation. Here the ONLY output is a 1PPS,
>> which
>> is divided by a fixed 2^23 from the internal DDS-generated frequency
>> (8.3xxxMHz). It is not possible to get both 10MHz and a 1PPS at the same
>> time. On the other hand the 8.3xxxMHz is tunable over many MHz.
>>
>> (One of the units is also suffering from a mishap. 15V connected to the
>> 1PPS output did some damage.)
>>
>
> My guess is that these all have the same part numbers because the hardware
> is the same.  But one chip is a CPLD which might have some very different
> programming depending on what the customer needed  I see some components
> where never installed on my unit, so it maybe more than just programming.

No, there are two different generations. The older based on 50.xxx MHz,
the newer on 60.0MHz (?) The older has a lot of stacked daughtercards on
the digital side. There are many differend sub-versions of these as well.
The newer generation seem to be one clean PCB. Look for picture links in
the recent archives.

--

   Björn




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