[time-nuts] End-of-Range: Oscilloquartz OCXO 8600-3

[Bob kb8tq]

Hi

Assuming it’s a unit with a 60C upper end temperature and that the 80C is the oven
temperature, that seems about right. The chart in the data sheet runs from 77C to 
89 C. 

If it was a conventional / old style 5 MHz 5th overtone AT cut crystal the Q of the resonator 
would be up around 5 million on a properly done part. That can happen one of two basic
ways. You can have a really low Rm or a really low Cm (of course it can. be a bit of both…).
If you happen to be in the “really low Rm regime, the tuning of the crystal isn’t going to be
any more crazy than one with much lower Q (and the same Cm). Yes, Co and the finish point
get in there as well ….

Bob

> On Dec 8, 2017, at 1:35 PM, Bert Kehren via time-nuts <time-nuts at febo.com> wrote:
> 
> What about 80 C is that normal for an 8600?
> Bert Kehren
> 
> 
> In a message dated 12/8/2017 11:32:14 A.M. Eastern Standard Time,  
> jn6wfo at gmail.com writes:
> 
> My  HP-103AR frequency standard has a similar problem. I have been advised
> to  take it apart and replace one of the capacitors in order to bring  the
> frequency back into the range of adjustment. Sounds like you have the  same
> problem.
> 
> Jeremy
> 
> 
> On Fri, Dec 8, 2017 at 7:52 AM paul  swed <paulswedb at gmail.com> wrote:
> 
>> I took a quick look at the  spec sheet.
>> It appears coarse adjustment is an option M and would  actually be a pot.
>> That speaks to another tuning diode for coarse? Or  a pot on pot
>> arrangement.
>> That sounds ugly.
>> Regards
>> Paul
>> WB8TSL
>> 
>> On Fri, Dec 8, 2017 at  10:17 AM, Bob kb8tq <kb8tq at n1k.org> wrote:
>> 
>>> Hi
>>> 
>>> It is quite possible that nothing is actually  broken and that the 
> crystal
>>> has simply drifted
>>> outside the tuning range. It should be pretty easy to spot the coarse
>>> tuning device once
>>> the package is open. I would bet you will  find a selected capacitor
>> across
>>> the coarse tune or  in
>>> series with the coarse tune. Changing the value of that cap  should 
> bring
>>> things back on
>>> frequency. I would avoid  changing caps across the EFC tuning diode.
>>> 
>>> Bob
>>> 
>>>> On Dec 8, 2017, at 8:05 AM, Ulf Kylenfall  via time-nuts <
>>> time-nuts at febo.com> wrote:
>>>> 
>>>> 
>>>> Gentlemen,
>>>> We have  an Oscilloquartz OCXO 8600-3that cannot any longer be 
> adjusted
>>> into 5,000,000 Hz.It is about 1 Hz out of 5 MHz and turning
>>> coarse/fineadjustment potentiometers cannot bring the frequencyinto  
> its
>>> specification.
>>>> Oven temperature is about +  80C accordingto the thermistor and the
>>> operating voltageis at 24  VDC.
>>>> Have Googled but the only thing that turns upis  datasheets w/o any
>>> details.
>>>> Before I take it  apart and start lookingfor obviously broken
>> components,
>>> isthere anyone that has a CLIP on this unit?
>>>> 73
>>>> 
>>>> Ulf Kylenfall - SM6GXV
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> -- 
> Sent from my iPad  4.
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