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

Mike Monett xde-l2g3 at myamail.com
Mon Nov 16 00:41:35 UTC 2009


Chuck Harris <cfharris at erols.com> wrote:
>
>What makes you think it needs to be CW, and cannot be pulsed and
>chirped?
>
>All it has to do is confuse the receiver enough so that you can't
>trust its readings.
>
>-Chuck

I said nothing about the type of modulation. The equipment I listed is
designed specifically to disrupt GPS. Presumably they use whatever
modulation method that gives the best results.

However, GPS is spread-spectrum, so it  inherently rejects noise that is
not correlated with the satellite signal. This means effective jamming
requires a lot more power than is available from a 9V transistor radio
battery, and even then, the range is only a few meters.

I made an error in calculating the average range per watt. The original
shows 8.75 meters/watt twice:

  (33.33 + 8.75 + 8.75 + 12 + 10 + 6.15) / 6 = 13.16 meters/watt.

It should be
  
  (33.33 + 8.75 + 12 + 10 + 6.15) / 5 = 14.046 meters/watt.

This does not affect the conclusion, which is it takes a lot more power to
disrupt GPS than it first appears. Putting jammers in Christmas toys would
accomplish little except to drain the batteries faster.

Mike Monett



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