[time-nuts] My Racal-Dana 1992
pete at petelancashire.com
Tue Dec 20 15:20:26 EST 2011
If I still have it, I'll take a picture of the 1992 i salvaged the
keyboard from. I was told it had
2 KW @ 700 MHz applied to it.
They do not make very good dummy loads.
On Tue, Dec 20, 2011 at 11:31 AM, Don Latham <djl at montana.com> wrote:
> Ah. That seems right, Charles, going by the behavior. In that case, what
> and where is the reference for the heater servo? The ambient
> temperature? Not too wise a choice, but what else? So it may be that the
> temperature is the controlling element but it, too, is an open system?
> It can be open, too, just second order?
> This is a knotty one!
> Charles P. Steinmetz
>> Don wrote:
>>>This is typical for an underdamped second order servo. The oscillation
>>>is the penalty for a shorter settling time. A critically damped system
>>>would not oscillate, but approach the final value smoothly in a
>>>longer time. It may have been designed for a slight overshoot...
>> Yes, I understand and I don't doubt that it is performing as
>> designed. My point was that most crystal oscillator frequency
>> adjustments (at least, the ones that I have seen) are open-loop
>> (variable capacitor or pot to a varactor diode). Finding the fine
>> frequency control apparently in a servo loop was a surprise. And it
>> cannot be a PLL or FLL, because there is only the one reference --
>> the one you are adjusting. Since the startup dynamics are so similar
>> to the fine frequency adjustment dynamics (not to mention that the
>> oven loop is pretty much the only possible servo in the oscillator),
>> the evidence appears strong that the fine frequency adjustment is an
>> oven temperature adjustment. Unless there is something truly
>> diabolical going on inside a 9462.
>> Best regards,
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> "Neither the voice of authority nor the weight of reason and argument
> are as significant as experiment, for thence comes quiet to the mind."
> R. Bacon
> "If you don't know what it is, don't poke it."
> Ghost in the Shell
> Dr. Don Latham AJ7LL
> Six Mile Systems LLP
> 17850 Six Mile Road
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