[time-nuts] MTI 260-0624-D OCXO

Bob Camp kb8tq at n1k.org
Wed Feb 17 07:13:43 EST 2016


Hi

What I have found on all of these is that the harder you look, the more you
toss out. I get a lot more from some batches than others to this or that point
in the testing. In some groups > 80% of them do not have working ovens or 
an output > 0 dbm. 

There are no hard specs on these surplus units (they are OEM specs). What
numbers should you check to past that? If you have a copy of that confidential
spec, how close is it to the general spec? Who knows. It would appear that in 
a lot of cases the “part number” refers to a package size and pinout. Past that
the other numbers are negotiable. 

If the objective is that magic sub 1x10^-12 ADEV from 0.1 second
out to 1,000 seconds ….. you will be sorting for a long time. Even at 3x10^-12 over
that entire range, you will sort a lot. Switch specs and just look at 1x10^-8
TC over -20 to +70, there is a lot of sorting to do. Same things with phase
noise, aging, harmonics, … on and on.

With the surplus stuff from China a sort seems to be the only way to do it. Either
you buy stuff that has been sorted over there or you sort it yourself. The testing 
involved in the more detailed specs is tough enough that the process can get
pretty complex. If there is somebody over there you can be *sure* is doing a full
test … I have not found them yet. 

Bob


> On Feb 16, 2016, at 10:49 PM, Bob Stewart <bob at evoria.net> wrote:
> 
> Hi Bob,
> 
> I've had essentially the same experience with a batch of 34310-Ts that I got from China.  Some are very good, most are good enough, some work but are useless for anything serious.  I haven't gone through enough of them to get any feel for the waste rate.  Hopefully it won't be more than 2 out of 10.
> 
> Bob
> 
> --------------------------------------------
> On Tue, 2/16/16, Bob Camp <kb8tq at n1k.org> wrote:
> 
> Subject: Re: [time-nuts] MTI 260-0624-D OCXO
> To: timenut at metachaos.net, "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
> Date: Tuesday, February 16, 2016, 8:27 PM
> 
> Hi
> 
> The 260’s that I have seen from inside the
> USA have been pretty good (not perfect, but
> certainly not dead). Most of the issues have
> been quibbles. Phase noise not quite in spec. 
> ADEV not quite as good as it might have been.
> 
> 
> Everything I have seen so
> far from China (260 or not) has been very hit or 
> miss. Stuff that is called “scrap for parts
> only” (like a pile of 10 Rb’s I have here) may turn
> up more working parts than something labeled
> “great / tested / buy now / first best great 
> product (a direct quote)“. I have tried the
> “buy a few and then go back” approach. There 
> has been little correlation between what I got
> the second time and what came in first. My
> conclusion (often stated) is that the salvage
> process over there is pretty brutal. 
> 
> Bob
> 
>> On
> Feb 16, 2016, at 7:58 PM, timenut at metachaos.net
> wrote:
>> 
>> I just
> received a 5Mhz OCXO from eBay (MTI 260-0624-D OCXO). After
> testing it,
>> it is clear that it is
> defective.
>> 
>>    1. It never heats up.
>> 
>>    2. The
> reference voltage is zero.
>> 
>>    3. Only noise is seen on the
> output pin.
>> 
>> I
> tested with a 12.54V, 2A supply voltage with around 30mV
> noise. That should
>> be sufficient to
> test.
>> 
>> All I was
> looking for was a 5Mhz signal whose frequency changed when
> the
>> adjustment pin was either tied to
> ground or the reference voltage. Never got
>> that far because I never go a signal at
> all.
>> 
>> The seller
> packed it well and shipped it promptly. I will see how he
> handles
>> it.
>> 
>> 
>> Mike
>> 
>> 
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