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)
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- [email protected]
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
