[time-nuts] STEL 1175 vice 1173

Magnus Danielson magnus at rubidium.dyndns.org
Wed May 14 17:17:46 UTC 2014

Hi Ed,

You could probably use a 32 bit DDS, but there will be a whole bunch of 
little trimmings you would have to do in the CPU code which would 
require quite a bit of (interesting) work. I would say it would be 
beyond the scope of most folks.


On 05/14/2014 06:53 PM, Ed Palmer wrote:
> Hi Corby,
> Thanks very much for the offer, but it looks like it would still be a
> big project to use an '1175 to replace an '1173.  I think I'll have to
> pass.
> The package difference (PLCC68 vs. PLCC44) would still require a
> daughterboard of some sort.  I've learned a little over the past week
> about NCOs and, if I'm right, reducing the clock speed from 45 MHz to 30
> MHz would partially compensate for the 32 vs. 48 bit difference.  The
> output frequency would be correct, but the waveform would have more
> harmonics.  Since the clock is derived from a 90 MHz signal, the
> reduction would be easy.  Whether that would have an adverse impact on
> the operation of the Datum 4065A is way beyond me.  It looks like both
> chips have a 12 bit output which is nice. The '1175 has more features
> than the '1173.  I'd have to study the data sheet to see if they can be
> configured to make the '1175 act like an '1173.
> For now, the plan is to try and source the '1173 in the 48-pin DIP
> package and do a (relatively) simple daughterboard to adapt the
> packages.  Even that will probably end up costing ~$150.  If that
> doesn't work out, there's the possibility of an FPGA replacement. That
> would likely allow replacing the AD9713 D/A converter as well as the
> STEL-1173.  It turns out that an NCO is a standard application in the
> FPGA world.
> Ed
> On 5/14/2014 9:13 AM, cdelect at juno.com wrote:
>> Hi,
>> I found two PLCC STEL 1175 in a rack mounted synthesizer I have.
>> I'd be willing to sell the chips.
>> Would they work?
>> Cheers,
>> Corby
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