[time-nuts] Old xtal filter

Bob Camp kb8tq at n1k.org
Sun Mar 6 21:55:18 EST 2016


Hi

> On Mar 6, 2016, at 8:15 PM, Magnus Danielson <magnus at rubidium.dyndns.org> wrote:
> 
> Hi,
> 
> On 03/07/2016 12:42 AM, Poul-Henning Kamp wrote:
>> --------
>> In message <CAF7oPz0SrwdMed1av2M_tkYw6K+EsR+akKa+kN623_Lf8KVf4g at mail.gmail.com>
>> , Joseph Gray writes:
>> 
>>> Assuming I made the pictures small enough, attached are two images of
>>> an very old crystal filter that a friend found. The strange thing
>>> about it is the bandwidth - 100 Hz. What could this have been used
>>> for, with such a narrow bandwidth?
>> 
>> The 100kHz center frequency pretty much rules out that it comes
>> from carrier telephony.
>> 
> 
> It does not match any of the FDM pilot tone systems that I've seen.
> It also does not match the TDM system rates, and this device seems old enough to almost precursor them.

If it’s a pilot tone, it’s probably part of some sort of tuned instrument rather than a full system. 

Bob

> 
> Cheers,
> Magnus
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