[time-nuts] Sidereal timekeeping

iovane at inwind.it iovane at inwind.it
Tue May 17 13:05:15 UTC 2011


Hi Jean-Louis,

I'm pleased to hear that you had success trying to modify such a crystal, 
though you had problems checking the frequency.
Regarding this aspect that I'm aware of, my idea is to "hear" to the 32kHz 
signal with a HP3586A selective voltmeter or a R&S VLF receiver. Further, as 
electric-guitar players do know, the 1 pps pulse of wristwatches is easily 
picked up by guitar pickups (many use wristwatches to check pick-ups). These 
pulses could be compared to pulses coming from, say, a properly set 3325A. And 
I will use a wall-clock machine which I suppose is stronger than a wristwatch.
As there is no issue, to some extent, with the lenght of wires between the 
crystal and the circuit at these frequencies, I was also speculating about a 
quasi-continuous monitoring of the trimming process, where for trimming I could 
use a disc of lapping sheet glued to a Dremel disc.

Well, just arrived another suggestion from Bob LaJeunesse too.

Regarding software applets (your other post) I have several of them, but as I 
said my problem is different.

Thanks,
Antonio I8IOV

>Hello list,
>I tried that a long time ago, but the trap I went into was that the 
>capacitance of the 'scope probe was pulling the frequency down, so I ended 
>with a crystal too high in frequency...
>I'm not sure that you can control the frequency without significantly 
>perturbing it. And waiting to check the rate between each tuning step would 
>take a long time...
>Regards,
>Jean-Louis
>----- Original Message ----- 
>From: "Bruce Griffiths" <bruce.griffiths at xtra.co.nz>
>To: "Discussion of precise time and frequency measurement" 
><time-nuts at febo.com>
>Sent: Tuesday, May 17, 2011 1:22 AM
>Subject: Re: [time-nuts] Sidereal timekeeping
>
>
>> Jim Lux wrote:
>>> On 5/16/11 2:58 PM, iovane at inwind.it wrote:
>>>> Neville,
>>>> at present I have not enough skill with micros to solve the problem.
>>>> I think I will try modifying a crystal. This would not be that difficult 
>>>> using
>>>> a lapping sheet or the like. And opening the can would be quite easy 
>>>> using hot
>>>> air.
>>>
>>> or a fine jeweler's saw or tubing cutter.
>>>
>>> As you pointed out, the crystals are cheap, so you can afford to ruin a 
>>> few while figuring out how to do it.
>>>
>>> (and then, remember us all, when you're a multi-billionaire having 
>>> cornered the market on sidereal rate crystals<grin>)
>>>
>>>
>> Since the 32 kHz crystal is likely to be a tuning fork form, one merely 
>> needs to shorten the tines to increase the frequency.
>> It may be feasible to do this without removing any of the electrode 
>> metallization.
>>
>> Bruce
>>
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