2021-02-09, 10:08:45
(This post was last modified: 2021-02-09, 10:09:32 by VA3KOT John.)
From G4JHT and G5VJ via SKCC forum:
Most folk do not know that the Zulu comes from the lettering of the time zones and zone Z runs right through Greenwich England the site of the original Naval Observatory and original master clocks. While UTC came about because atomic clocks get out of step with the Sun. So GMT needs to be fiddled to get them back in sync every so often.
Each zone extends seven and a half degrees on either side of the zone lines. The zone lines are spaced at 15 degree intervals, and lettered A,B,C.. going East from Greenwich, and Y,X,W... going West. This puts NY just in zone -4 "V" , Victor (centered on 90E); Chicago just in zone -5 , "U", Uniform (centered on 105E?); and San Francisco to the West of the zone line, in zone -8 (centered on 120E) "R", Romeo.
This stuff is still used at sea world wide and it was a standard procedure to "flog the clocks" back by 30 minutes a night on the run from the UK to NY. the object being to make ships noon correspond to solar noon for sun sights - still required in the age of GPS as GPS is classes a mere aid to navigation!
Hope the above is of interest and not too long winded.
73, OldBlueBear-G4JHT-Dave EI0DB.
You may be interested that there is no Juliet category - it skips from Hotel, India to Kilo, Lima. Which is why 'spending J time' was (still is?) a euphemism for slacking off or spending 'no-time.' Doing nothing.
de G5VZ ..
Most folk do not know that the Zulu comes from the lettering of the time zones and zone Z runs right through Greenwich England the site of the original Naval Observatory and original master clocks. While UTC came about because atomic clocks get out of step with the Sun. So GMT needs to be fiddled to get them back in sync every so often.
Each zone extends seven and a half degrees on either side of the zone lines. The zone lines are spaced at 15 degree intervals, and lettered A,B,C.. going East from Greenwich, and Y,X,W... going West. This puts NY just in zone -4 "V" , Victor (centered on 90E); Chicago just in zone -5 , "U", Uniform (centered on 105E?); and San Francisco to the West of the zone line, in zone -8 (centered on 120E) "R", Romeo.
This stuff is still used at sea world wide and it was a standard procedure to "flog the clocks" back by 30 minutes a night on the run from the UK to NY. the object being to make ships noon correspond to solar noon for sun sights - still required in the age of GPS as GPS is classes a mere aid to navigation!
Hope the above is of interest and not too long winded.
73, OldBlueBear-G4JHT-Dave EI0DB.
You may be interested that there is no Juliet category - it skips from Hotel, India to Kilo, Lima. Which is why 'spending J time' was (still is?) a euphemism for slacking off or spending 'no-time.' Doing nothing.
de G5VZ ..
John VA3KOT
Blog: HamRadioOutsideTheBox.ca
Blog: HamRadioOutsideTheBox.ca