[time-nuts] Wavecrest DTS-2077 Teardown

Bruce Griffiths bruce.griffiths at xtra.co.nz
Wed Aug 21 01:32:19 EDT 2013


A time interval counter or equivalent with less acoustical noise and 
internal jitter than the Wavecrest  would be nice.

Bruce

Said Jackson wrote:
> Guys,
>
> The dts needs to be driven by square waves, driving them with sine waves gives jitter values that are displayed significantly too high due to trigger noise.
>
> Holzworth makes a small sine wave to square wave converter that can drive 50 ohms. Use a DC block and an attenuator on the cmos output to avoid damaging the dts inputs. You can make your own converter using a single fast cmos gate, resistor, and blocking cap. By using hand-selected gates I was able to achieve less jitter with that circuit than what the Holzworth box was able to achieve.
>
> Doing that conversion can bring down the measured rms jitter on a very good 10MHz sine wave source from 10ps+ to less than 2ps - basically at or below the noise floor of the dts.. Once you run at the units' noise floor, you know your source is quite good..
>
> Bye,
> Said
>
> Sent From iPhone
>
> On Aug 20, 2013, at 18:51, Ed Palmer<ed_palmer at sasktel.net>  wrote:
>
>    
>> Adrian,
>>
>> I used Timelab to assess the reaction of the DTS-2077 to different sine wave inputs.  The differences in the noise floor are surprising.  The attached picture was made by taking the output of an HP 8647A Synthesized Generator through a splitter, and then through different lengths of cables to the inputs of the DTS-2077.  The combination of splitter and cable loss meant I couldn't get +7 dbm @ 1 GHz.  If I could have, the 1 GHz line might have been lower than it was.
>>
>> Ed
>>
>> On 8/20/2013 4:42 PM, Adrian wrote:
>>      
>>> Ed,
>>>
>>> thanks for posting!
>>>
>>> I'm still looking for a MUX board for my faulty 2077.
>>>
>>> Is there anyone using a DTS-207x with TimeLab?
>>>
>>> Adrian
>>>
>>>
>>> Ed Palmer schrieb:
>>>        
>>>> FYI, I did a teardown on my Wavecrest DTS-2077.  It's posted here:
>>>>
>>>> http://www.eevblog.com/forum/testgear/wavecrest-dts-2077-teardown
>>>>
>>>> Ed
>>>>          
>> <DTS-2077 Noise Floor.png>
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