[time-nuts] getting a grip on 10811 drift (trying to read my instruments)

[WarrenS]

Hold the Up arrow down for >3 sec and put your counter into the 10 sec 
range.
That will give you another digit of resolution. Now the LS Digit will be 
1e-10 / count enough to test short term delta stability of many things.

ws

----- Original Message ----- 
From: "Chris Howard" <chris at elfpen.com>
To: "WarrenS" <warrensjmail-one at yahoo.com>
Cc: "Discussion of precise time and frequency measurement" 
<time-nuts at febo.com>
Sent: Thursday, November 15, 2012 6:57 PM
Subject: Re: [time-nuts] getting a grip on 10811 drift (trying to read my 
instruments)


>
> You all were right, my targeting of the 50 ohm resistor
> across the oscillator output does not seem to have solved the
> problem.   A good thing to do, probably, but not the answer.
>
> While I was all excited about the resistor change I also
> mapped out the control voltage (EFC) vs frequency change.
> I wrote it out but didn't pay much attention.  Now
> I've been pondering over that a bit.  My next theory
> is that my EFC maybe isn't really doing very much.
>
> First I need to know if I am reading this right.
> My frequency counter is a Racal 1992  It reads
> 9.99999997^6   as I write.  A total of 9 digits
> with a smaller "6" to the right.
>
> If I read this correctly, I'm looking at
> 9,999,999.97  Hz ?  If so, then I've got an EFC problem.
>
> My EFC mapping looks like this (this was done before
> I adjusted the coarse control)
>
>
> -4.94 VDC         9,999,999.95
> -3.70             9,999,999.95
> -1.24             9.999.999.93
> 0 VDC   9,999,999.93
> +1.21             9,999,999.92
> +2.44             9,999,999.92
> +3.67             9,999,999.91
> +4.90 VDC   9,999,999.90
>
> It doesn't look to me like I am getting anything
> like 1/2 hertz range using the EFC.  If that's
> the case than my controller card is frantically
> steering but not getting the desired result.
>
> Or, if I'm reading it wrong,  maybe that last digit
> is 0-5 meaning 1/2 a hertz and I am all wet (again).
>
> This particular oscillator came out of an old HP counter
> and I believe the EFC was wired to ground.  So maybe
> the thing has never been exercised.  Are there versions
> of the 10811 that don't have EFC guts inside?
>
> Hope I'm not boring you all to death.
>
> Chris
> w0ep
>
>
>
> On 11/9/2012 11:26 PM, WarrenS wrote:
>> Chris
>>
>> HP 10811 can't drift that much that fast unless something is near broken, 
>> or being connected wrong like gnds or PS voltage.
>> Check the operation of the oven.