Chuck Harris <cfhar...@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 _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.