[time-nuts] National Positioning, Navigation, and Timing (PNT) Resilience and Security Act of 2015, H.R. 1678.
brooke at pacific.net
Fri Mar 27 16:31:12 EDT 2015
Here's a copy of an email I just sent my U.S. assemblyman.
One of my passions is precision time and frequency, a subject where I have a considerable amount of knowledge. It turns
out the navigation is imminently related to precision time. GPS and LORAN both work by making precision timing
A few years ago the LORAN-C system was decommissioned. I think that was a mistake because:
1) There was a new eLORAN-C system in the works that would modernize it adding new features.
If I had an input on the enhanced LORAN-C it would be the addition of bits for Daylight Saving Time and leap seconds
as well as date and time.
Some parts of the U.S. have a very difficult time getting reception of the WWVB "atomic clock" radio signal, but
could easily receive the eLORAN-C signal.
PS GPS does not contain Daylight Saving Time or Leap Second bits and so can not be used to discipline domestic time
of day clocks.
2) The cost of maintaining this low frequency system is very small compared to the cost for the GPS system.
3) Because the ground based low frequency (100 kHz) LORAN-C transmitters are very powerful it's almost impossible to jam
them. I've never heard of a case of LORAN-C being jammed either accidental or on purpose. This is far different from
GPS which can be jammed with a hand held battery powered device. There have been numerous cases of unintentional GPS
jamming including one at a major East coast airport (a truck driver with a jammer to prevent his boss knowing where he
was) to the Monterrey Bay area (a sail boat with a defective amplified TV antenna).
So, I support bringing back LORAN-C and further bringing the system up to date with eLORAN-C.
Here's my web page with a table of LORAN-C stations applicable to the U.S.
Note that other countries are still using LORAN-C (maybe some flavor of eLORAN0C).
There is a new GPS "L5" safety of life signal being just starting to be deployed now which would notify an air crew that
their GPS signal was being jammed. I think that military GPS (which requires classified keys) can detect jamming, but
neither of these can overcome the jamming. A dual system that used both eLORAN-C and GPS would be much more tolerant of
a jamming attempt (either deliberate or accidental).
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