Even 10 KM is pretty useful. If the thing were solar powered with a supercap "battery" it could easly transmit for say 2 minutes per hour w/ significant power. It'd be hard to find if the on times were generated by a multiple fedback CMOS shift register.
-John ================ > Mike > > Instead of relying on the dubious claims of those marketing an extremely > inefficient jammer it would be better to actually do some simple > calculations. > > Typical commercial receivers stop tracking with a Jam to signal ratio of > not more than 60dB or so: > http://www.gpsworld.com/gps/jamming-gps-778 > > The input signal level at the receiver input is around -160dBW. > > A 1W ERP source with an isotropic hemispheric radiation pattern will > exceed the the required jamming signal strength for distances less than > several tens of kilometers. > > This estimate is consistent with the fact that LO parasitic radiation > from TV systems on boats have been known to jam GPS for distances of > several kilometers. > > Bruce > > Mike Monett wrote: >> Chuck Harris<[email protected]> 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 -- [email protected] > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
