[time-nuts] 10811

[Richard (Rick) Karlquist]

Yes, 5.1V Zeners (or something like that) have a "magic" zero tempco if
you put a conventional diode in series with it.  I used to know
stuff like that during the Jurassic period.

However, the diode in the 10811 is ovenized, so that is not so 
important. 6.2V was chosen to get +/- 5V tuning range, which was 
probably a spec inherited from the 10544.  Everything was done for a 
reason relevant to HP, which may or may not be a reason relevant to you.

The frequency of the 10811 is more sensitive to the temperature of
the oscillator transistor (a selected 2N5179) than the diode.  This
inspired the E1938A.

Rick

On 11/18/2014 2:31 PM, Brooke Clarke wrote:
> Hi Rick:
>
> When working on Tunnel Diode amplifiers we used (AFAICR) 5.1 V Zener
> diodes to stabilize the lower voltage that drive the diode.
> 5.1V was supposed to have excellent temperature characteristics in terms
> of repeatability (don't remember if low noise was part of the selection
> criteria).
> http://www.prc68.com/I/Aertech.shtml#TDA
> The boards with the terminals have the Zener and a custom compensation
> network using both Veco (spelling?) (-TC) and Balco (+TC) and fixed
> resistors so that the gain stays constant over mil temperature ranges.
>
> Mail_Attachment --
> Have Fun,
>
> Brooke Clarke
> http://www.PRC68.com
> http://www.end2partygovernment.com/2012Issues.html
> http://www.prc68.com/I/DietNutrition.html
> Richard (Rick) Karlquist wrote:
>>
>>
>> On 11/17/2014 5:54 PM, Bert Kehren via time-nuts wrote:
>>> I ground one side of the tuning diode and use the 2 to 12 V as the
>>> external
>>>   OCXO for my FRK's along with increasing the time constant. I have not
>>> verified it but I think removing the zener Voltage should also
>>> improve  ADEV.
>>> Bert Kehren
>>>
>>
>> The choice for the Zener diode came from my old boss at HP,
>> who was very knowledgeable about using discrete zener diodes
>> as low noise references.  According to him, this particular
>> part number has very respectable noise.  This is just something
>> you have to know experientially, there is no theory of zener
>> noise AFAIK.  You might try measuring the noise of the 6.2V
>> reference voltage directly at baseband, and then multiplying
>> by the 1 Hz/volt sensitivity.  Let us know your results.
>>
>> Rick Karlquist N6RK
>> (Now retired from HP/Agilent/Keysight)
>>
>>
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