[time-nuts] semi-OT: comparison of two 10x scope probes / cheap OCXO

Bruce Griffiths bruce.griffiths at xtra.co.nz
Fri Mar 18 06:38:46 UTC 2011


The cheap probes probably lack the resistive inner conductor in their 
interconnecting coaxial cables.
This results in a poorly damped transient response.

Bruce

Eric Garner wrote:
> I too, fell for the siren song of cheap Chinese probes. 2 years after
> I bought 4 of them, only one has not failed. However, my 1980's
> vintage probes from Tek still work dandily.
>
>
>
> On Thu, Mar 17, 2011 at 12:47 PM, beale<beale at bealecorner.com>  wrote:
>    
>> Yes, I am controlling the OCXO frequency with a voltage input (center tap of 10k trimpot from +5V to ground). I hooked up my custom 26 MHz PIC divider* and was able to trim the OCXO to match the output of my GPS 1pps signal to better than 1E-9 (at least for short periods of time).
>>
>> These parts draw about 60 mA at +5V in operation in a 23 C ambient environment, after a brief one-time warmup pulse of about 200 mA. The can gets a bit warm if left open. I taped a small thermistor against the case, and made a little styrofoam box to nest snugly over it and measured the can case temp to reach about 50 C when thus insulated.
>>
>> I am accumulating some performance data on the two units I have and can post it online if anyone is interested.  (actually, I was thinking of buying a bunch more before posting the data, because the price seems too good to be true).
>>
>> * http://www.bealecorner.org/best/measure/time/source/
>>
>> Scott Newell wrote:
>>      
>>> That's a great price for any OCXO. Do they have EFC? (I can't tell from the part number in the auction photo.)
>>>        
>> At 01:41 PM 3/17/2011, beale wrote:
>>     output of a 26 MHz Pletronics OCXO in a 14DIP can (by the way these go for $2 online, the cheapest OCXO I've seen).
>>
>>
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>>      
>
>
>    





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