[time-nuts] Antique precision timing device without electronics
phk at phk.freebsd.dk
Sat Mar 18 04:47:36 EDT 2017
In message <20170317220437.4A4FF40605C at ip-64-139-1-69.sjc.megapath.net>, Hal Murray writes:
>eric at scace.org said:
>> Frequencies around 15 Hz were common on early 20th century cables,
>> depending on the degree of success in compensating for the inherent
>> capacitance on a cable thousands of miles long surrounded by conductive
>> sea water.
>Is the sea water relevant?
Not in a coaxial cable, unless it gets into the cable.
Most telegraph cables where not coaxial and used the sea-water as return path.
>Does enough energy leak through the shield so that it matters? How well does
>coax work at low frequencies?
Coax is near perfect at low frequencies, but the lengths of these
cables introduced geophysics as a number of sources of noise.
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