[time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)

J. Forster jfor at quik.com
Sun Nov 15 04:00:39 UTC 2009


Agreed.

Furthermore, a GPS jammer is VERY hard to locate because the signal levels
are so low.

An effective LORAN jammer could easily be DF'd with a foot sized loop and
tuning capacitor resonating at 100KHz, diode detector, and a set of
headphones. It would be IMPOSSIBLE to hide.

If a LORAN transmitter were destroyed by a terrorist team, a backup could
be in operation in hours. A damaged GPS system could easily take many
months or even years to fix.

-John

================


> And all the GPS goodness can easily be disabled by a missile and a
> near nuclear burst or a portable handheld jammer at the airport.
> The portable handheld jammer is a very real threat to GPS due to the
> signal levels from the satellite.
>
> Now they are trying to revive a miswired SVN and add it to the network.
>
> It is very hard to jam the LORAN signal without a high power jammer.
> If a LORAN station is taken out by enemy action, it is not
> unreasonable to rebuild or replace it.
>
> GPS is just too fragile to be heavily relied on.
>
> I know that we do it every day, but, you need to have a backup
> navigation system.
>
> LORAN is time proven to be functional and the technology is in place
> on a number of platforms to utilize it.
>
>
> 73
> Glenn
> WB4UIV
> ETCS(SS) USN Retired (Electronic Navigation)
>
> At 10:21 PM 11/14/2009, Francesco Ledda wrote:
>>LORAN is a good back up, but it has problems and limitations.  Navigating
>>next to a storm can overwhelm the receiver and make it unusable.  The
>> LORAN
>>system doesn't have a build in accuracy degradation system like GPS(RAIM
>> -
>>receiver autonomous integrity monitoring), and this make LORAN unfit to
>> fly
>>Non-Vertical Guidance approaches. GPS with its accurate positioning, fast
>>update rate and WAAS make is an awesome aircraft navigation system that
>> can
>>replace almost all NAVAIDS including ILS. Today with GPS, we can fly in
>>instrument conditions from take off to landing without ever tuning any
>>external NAVAID; not even INS can't do that. It is pretty amazing to me!
>>
>>
>>
>>
>>
>>
>>-----Original Message-----
>>From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com]On
>>Behalf Of Hal Murray
>>Sent: Saturday, November 14, 2009 7:13 PM
>>To: Discussion of precise time and frequency measurement
>>Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference
>>oscillator accuracy)
>>
>>
>>
>> > I've read and heard from this forum as well as a number of other
>> > sources that GPS can be easily jammed.  What makes GPS so vulnerable?
>> > How can it be jammed?
>>
>>The signal is very very very weak.  The question is not how can it be
>>jammed,
>>but rather how can you find the signal at all.
>>
>>There was a recent message here reporting on the 5th harmonic of a small
>> 315
>>MHz radio link wiping out GPS for a 1/2 mile:
>>   http://www.mail-archive.com/time-nuts@febo.com/msg22033.html
>>
>>Here is a good story:
>>   Unjamming a Coast Harbor
>>   James R. Clynch, Andrew A. Parker, George Badger,
>>   Wilbur R. Vincent, Paul McGill, Richard W. Adler
>>   GPS World, Jan 1, 2003
>>   http://www.gpsworld.com/gps/system-challenge/the-hunt-rfi-776
>>
>>
>>
>>--
>>These are my opinions, not necessarily my employer's.  I hate spam.
>>
>>
>>
>>
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