Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-25 Thread jimlux
On 8/25/16 8:12 PM, Bill Metzenthen wrote: On 26/08/16 08:14, Hal Murray wrote: billm...@gmail.com said: If the conductor also has magnetic properties (e.g. if iron were used) then magnetic saturation could be an issue. Ah... Sorry I wasn't clear. How about Is skin depth an interesting con

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-25 Thread Bill Metzenthen
On 26/08/16 08:14, Hal Murray wrote: billm...@gmail.com said: If the conductor also has magnetic properties (e.g. if iron were used) then magnetic saturation could be an issue. Ah... Sorry I wasn't clear. How about Is skin depth an interesting concept if you are using materials commonly use

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-25 Thread Dave Brown
; Cc: Sent: Wednesday, August 24, 2016 11:06 AM Subject: Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre Don't over-interpret the 50 Hz aspect, I don't remember those details from 4.5 months back or so, as I already indicated. I can ask on the details tomorr

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-25 Thread Alex Pummer
to shield against DC and low frequency magnetic field usually high permeability magnetizable material -- Permalloy, Mu-metal or similar is used, the field concentrates in the high permeability material and "behind it" is no left over magnetic field 73 Alex On 8/25/2016 11:10 AM, Magnus Dani

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-25 Thread Hal Murray
billm...@gmail.com said: > If the conductor also has magnetic properties (e.g. if iron were used) then > magnetic saturation could be an issue. Ah... Sorry I wasn't clear. How about Is skin depth an interesting concept if you are using materials commonly used for magnetic shielding, for exa

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-25 Thread Bill Metzenthen
On 26/08/16 06:33, Hal Murray wrote: billm...@gmail.com said: Skin depth is probably a good place to start with in roughly estimating the thickness needed. In copper at 50 Hz, ... Is skin depth an appropriate concept for magnetic shielding? Or does it get messed up by saturation? Skin dep

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-25 Thread Hal Murray
billm...@gmail.com said: > Skin depth is probably a good place to start with in roughly estimating the > thickness needed. In copper at 50 Hz, ... Is skin depth an appropriate concept for magnetic shielding? Or does it get messed up by saturation? -- These are my opinions. I hate spam.

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-25 Thread Magnus Danielson
Hi, On 08/25/2016 11:04 AM, Bill Metzenthen wrote: On 25/08/16 18:25, Poul-Henning Kamp wrote: In message <1057836989.2088307.1472104857885.javamail.ya...@mail.yahoo.com>, Br uce Griffiths writes: You'd need a rather thick copper jacket to shield effectively against the 50Hz magnetic

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-25 Thread Bill Metzenthen
On 25/08/16 18:25, Poul-Henning Kamp wrote: In message <1057836989.2088307.1472104857885.javamail.ya...@mail.yahoo.com>, Br uce Griffiths writes: You'd need a rather thick copper jacket to shield effectively against the 50Hz magnetic field. As in: A good-sized fraction of the waveleng

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-25 Thread Bob kb8tq
Hi There is also the minor issue of putting the (very thick) layers on in a spiral around the "core". You put one layer on clockwise and the next counter clockwise. Since the materials are quite springy, controlling the whole process through heat treating is a real chore. Bob > On Aug 25, 201

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-25 Thread Charles Steinmetz
Bruce wrote: As long as you don't saturate it, bend it, hit it or drop it. And that is AFTER you form it to shape and then anneal it in a Hydrogen atmosphere. You may (probably would) need several layers, perhaps of different high-permeability alloys, with a thick outermost layer of soft i

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-25 Thread Poul-Henning Kamp
In message <1057836989.2088307.1472104857885.javamail.ya...@mail.yahoo.com>, Br uce Griffiths writes: >You'd need a rather thick copper jacket to shield effectively >against the 50Hz magnetic field. As in: A good-sized fraction of the wavelength if I recall :-) Electric fields are so mu

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-24 Thread Bruce Griffiths
etic >> >> but maybe doping can make them susceptible? >> >> >> >>> On Wed, 24 Aug 2016 09:31:57 +1200, you wrote: >> >>> >> >>> What is the coupling mechanism giving rise to the 50Hz > disturbance? >> >>> DaveB, N

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-24 Thread André Esteves
.org/wiki/Piezomagnetism >> >> >> >> I do not know if optical fibers are even slightly antiferromagnetic >> >> but maybe doping can make them susceptible? >> >> >> >>> On Wed, 24 Aug 2016 09:31:57 +1200, you wrote: >> >

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-24 Thread Bruce Griffiths
I do not know if optical fibers are even slightly antiferromagnetic > >> but maybe doping can make them susceptible? > >> > >>> On Wed, 24 Aug 2016 09:31:57 +1200, you wrote: > >>> > >>> What is the coupling mechanism giving rise to the 50Hz di

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-24 Thread Bob kb8tq
2016 09:31:57 +1200, you wrote: >>> >>> What is the coupling mechanism giving rise to the 50Hz disturbance? >>> DaveB, NZ >>> >>> - Original Message - >>> From: "Magnus Danielson" >>> To: >>> Cc: >>

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-23 Thread Magnus Danielson
ise to the 50Hz disturbance? DaveB, NZ - Original Message - From: "Magnus Danielson" To: Cc: Sent: Wednesday, August 24, 2016 8:54 AM Subject: Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre ... These links is in principle not very complex, but they are

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-23 Thread David
t;From: "Magnus Danielson" >To: >Cc: >Sent: Wednesday, August 24, 2016 8:54 AM >Subject: Re: [time-nuts] Optical link connects atomic clocks over 1400 km of >fibre > >> ... >> >> These links is in principle not very complex, but they are regardless

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-23 Thread Magnus Danielson
se to the 50Hz disturbance? DaveB, NZ - Original Message - From: "Magnus Danielson" To: Cc: Sent: Wednesday, August 24, 2016 8:54 AM Subject: Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre The presentations and posters at 8FSM and EFTF York have b

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-23 Thread Hal Murray
tract...@ihug.co.nz said: > What is the coupling mechanism giving rise to the 50Hz disturbance? My guess would be mechanical. Maybe from a nearby transformer. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.c

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-23 Thread Dave Brown
What is the coupling mechanism giving rise to the 50Hz disturbance? DaveB, NZ - Original Message - From: "Magnus Danielson" To: Cc: Sent: Wednesday, August 24, 2016 8:54 AM Subject: Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre The present

Re: [time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-23 Thread Magnus Danielson
The presentations and posters at 8FSM and EFTF York have been interesting. The PTB link-end is even more stable than the clock, but only in frequency stability. More links is planned, among those between LNE-SYRTE at Paris Observatory and NPL outside London. Such links aid in the comparison of

[time-nuts] Optical link connects atomic clocks over 1400 km of fibre

2016-08-22 Thread André Esteves
Some interesting developments in european atomic clocks. http://physicsworld.com/cws/article/news/2016/aug/22/optical-link-connects-atomic-clocks-over-1400-nbsp-km-of-fibre http://www.nature.com/articles/ncomms12443 The time kept by atomic clocks in France and Germany has been compared for the f