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

[Mike Monett]

  Chuck Harris <cfharris at erols.com> wrote:

  > I guess the point you folks aren't getting is you can make  a very
  > effective local GPS jammer that runs off of a 9V  transistor radio
  > battery, and  will  last for several weeks. It can be  done  for a
  > total cost  of  a  few bucks per jammer....  search  the  web, the
  > designs are out there.

  > Toss the  GPS jammers indiscriminately around  the  landscape, and
  > you put GPS out of business for a very low cost.

  >-Chuck Harris

  I'm not so sure that would be very effective. A typical  9v alkaline
  contains about 900 milliamp/hours at low current drain.

  Two weeks  is  24 * 7 * 2 = 336 hrs. Assuming  100%  efficiency, the
  battery would  supply  0.9  / 336 =  0.00267A,  or  0.024  watt, not
  including the drop in voltage after the first few dozen hours.

  There are  quite a few commercial jammers  designed  specifically to
  jam GPS signals. These are extremely illegal, but they do  give some
  idea of the range that could be expected.

  Below is  a list of the specified range and power.  I  calculate the
  highest ratio to get the meters per watt.

  GMW12 Cellular & GPS L1 Jammer

  Block cellular signals and GPS L1 system in the same time

  Jamming Range : Average 40 meters radius
  Output Power  : Total 6.5 Watt

  ratio : 40/6.5 = 6.15 meters/watt

  <http://www.tayx.co.uk/gmw12-gps-mobile-jammer.html>

  KYG0014 Fixed Jammer

  Output Power  : 2000mw
  Jamming Range : 15~20 meters

  ratio : 20/2 = 10 meters/watt

  <http://www.alibaba.com/product-gs/204091726/Fixed_GPS_jammer.html>

  KYG0017 Powerful GPS signal jammer

  Output power : 25W
  Range        : radius 100-300meters

  ratio : 300 / 25 = 12 meters/watt

 
<http://www.alibaba.com/product-gs/213377763/Powerful_GPS_signal_jammer.html>

  KYG0013 Car GPS jammer

  Output power : 800mW
  Range        : radius 10-15 meters

  ratio : 15 / 0.8 =  8.75 meters/watt

  <http://www.alibaba.com/product-gs/204037628/KYG0013_Car_GPS_jammer.html>

  KYP0050 Handheld GPS/GSM signal Jammer / blocker

  output power  : 300mw
  jamming range : 2~10 meters

  ratio : 10 / 0.3 =  33.33 meters/watt

 
<http://www.alibaba.com/product-gs/206648711/KYP0050_Handheld_GPS_GSM_signal_Jammer_blocker.html>

  The average ratio is:

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

  The highest claimed performance is the KYP0050, with 33 meters/watt.

  Assuming the  9V  battery jammer has 100%  RF  efficiency  and equal
  ratio, the  jamming range would be 33.33 * 0.024 =  0.799  meters or
  about 2.62 feet.

  However, a  jammer  would   require   crystal   control  to  stay on
  frequency. There  are no crystals for L1, so a  multiplier  would be
  needed. The  actual power output would be much lower,  so  the range
  would be much less.

  Another example,  a 1500mAh rechargable pocket jammer has a  5 meter
  range, and only lasts 2~3 hrs:

  GMT04 Pocket GPS Jammer

  Jaming Range      : Average 5 meters radius
  Current & Voltage : 200mA DC12V / AC120~140V
  Battery           : 1,500mAh

  battery life 2~3 hours, recharge needs 3~4 hours

  <http://www.tayx.co.uk/gmt04-pocket-gps-jammer.html>

  So a  9V transistor radio battery jammer doesn't seem like  it would
  present much of a danger.

  Mike Monett