Re: [time-nuts] The Demise of LORAN (was Re: Reference oscillator accuracy)
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
Mike Monett wrote:
Chuck Harris cfharris@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
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Chuck,
Chuck Harris wrote:
What makes you think it needs to be CW, and cannot be pulsed and
chirped?
May I roll in a noise jammer into the debate?
All it has to do is confuse the receiver enough so that you can't
trust its readings.
Depends on the goal. For some strategies, blackout is the goal, for some
getting the readings go haywire every once in a while suffice.
Cheers,
Magnus
Magnus Danielson wrote:
Chuck,
Chuck Harris wrote:
What makes you think it needs to be CW, and cannot be pulsed and
chirped?
May I roll in a noise jammer into the debate?
Absolutely! They can be extremely power efficient. Raise the noise
floor in the vicinity of the receiver, and it is all done.
Probably the easiest solution would be to take a PN source and use it
to drive a pulser that pulses a chirp oscillator. If you are feeling
really polite, you could put a bandpass filter on the thing to protect
other services.
All it has to do is confuse the receiver enough so that you can't
trust its readings.
Depends on the goal. For some strategies, blackout is the goal, for some
getting the readings go haywire every once in a while suffice.
Agreed!
My 9V battery suggestion was for a localized blackout device. You only
have to make the receiver question each satellite's signal often enough
for it to rule it out. No way is CW necessary, or even desirable.
As John suggested, someone (say the Chinese) could put these things in
battery operated stuffed animals, and set them up to jam a little bit
now and then. After Xmas, the GPS landscape would be littered with these
little stealth jammers, and willing supplicants to replace their batteries.
-Chuck
Or even into MP3 players, iPods, laptops, or cell phones. Then they'd
wander all over the place too. With the latter two hosts, they could even
be controlled remotely and even be fairly powerful. Would you notice
having to recharge your battery a bit more often?
-John
===========
Magnus Danielson wrote:
Chuck,
Chuck Harris wrote:
What makes you think it needs to be CW, and cannot be pulsed and
chirped?
May I roll in a noise jammer into the debate?
Absolutely! They can be extremely power efficient. Raise the noise
floor in the vicinity of the receiver, and it is all done.
Probably the easiest solution would be to take a PN source and use it
to drive a pulser that pulses a chirp oscillator. If you are feeling
really polite, you could put a bandpass filter on the thing to protect
other services.
All it has to do is confuse the receiver enough so that you can't
trust its readings.
Depends on the goal. For some strategies, blackout is the goal, for some
getting the readings go haywire every once in a while suffice.
Agreed!
My 9V battery suggestion was for a localized blackout device. You only
have to make the receiver question each satellite's signal often enough
for it to rule it out. No way is CW necessary, or even desirable.
As John suggested, someone (say the Chinese) could put these things in
battery operated stuffed animals, and set them up to jam a little bit
now and then. After Xmas, the GPS landscape would be littered with these
little stealth jammers, and willing supplicants to replace their
batteries.
-Chuck
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and follow the instructions there.
Considering that the GPS antenna in aircrafts is mounted on top of fuselage,
and that its radiation pattern is upward, it seems that a ground jammer will
have an uphill battle.
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com]On
Behalf Of J. Forster
Sent: Sunday, November 15, 2009 6:28 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference
oscillator accuracy)
Or even into MP3 players, iPods, laptops, or cell phones. Then they'd
wander all over the place too. With the latter two hosts, they could even
be controlled remotely and even be fairly powerful. Would you notice
having to recharge your battery a bit more often?
-John
===========
Magnus Danielson wrote:
Chuck,
Chuck Harris wrote:
What makes you think it needs to be CW, and cannot be pulsed and
chirped?
May I roll in a noise jammer into the debate?
Absolutely! They can be extremely power efficient. Raise the noise
floor in the vicinity of the receiver, and it is all done.
Probably the easiest solution would be to take a PN source and use it
to drive a pulser that pulses a chirp oscillator. If you are feeling
really polite, you could put a bandpass filter on the thing to protect
other services.
All it has to do is confuse the receiver enough so that you can't
trust its readings.
Depends on the goal. For some strategies, blackout is the goal, for some
getting the readings go haywire every once in a while suffice.
Agreed!
My 9V battery suggestion was for a localized blackout device. You only
have to make the receiver question each satellite's signal often enough
for it to rule it out. No way is CW necessary, or even desirable.
As John suggested, someone (say the Chinese) could put these things in
battery operated stuffed animals, and set them up to jam a little bit
now and then. After Xmas, the GPS landscape would be littered with these
little stealth jammers, and willing supplicants to replace their
batteries.
-Chuck
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Chuck Harris wrote:
Magnus Danielson wrote:
Chuck,
Chuck Harris wrote:
What makes you think it needs to be CW, and cannot be pulsed and
chirped?
May I roll in a noise jammer into the debate?
Absolutely! They can be extremely power efficient. Raise the noise
floor in the vicinity of the receiver, and it is all done.
Probably the easiest solution would be to take a PN source and use it
to drive a pulser that pulses a chirp oscillator. If you are feeling
really polite, you could put a bandpass filter on the thing to protect
other services.
The schematic out there is a PN source feeding an OCXO and then
amplified. Crystal loop to keep fairly centered. More or less the same
as personalized phone jammers do. Very simple design.
All it has to do is confuse the receiver enough so that you can't
trust its readings.
Depends on the goal. For some strategies, blackout is the goal, for
some getting the readings go haywire every once in a while suffice.
Agreed!
My 9V battery suggestion was for a localized blackout device. You only
have to make the receiver question each satellite's signal often enough
for it to rule it out. No way is CW necessary, or even desirable.
True.
As John suggested, someone (say the Chinese) could put these things in
battery operated stuffed animals, and set them up to jam a little bit
now and then. After Xmas, the GPS landscape would be littered with these
little stealth jammers, and willing supplicants to replace their batteries.
Well, then you have to consider what the potential gain would be from
such an attack. I fail to see the upside of that particular scenario. It
would draw the attention over to them and in a field I think they rather
stay calm about. Their ability to pull it off as such should not be
doubted, but their resoning for it. Rather inefficient actually.
Cheers,
Magnus
Chuck Harris cfharris@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
See my earlier post. Briefly:
Antennas do not have an infinite front-to-back ratio. (<40 dB)
The path loss from a surface jammer to a plane (10 miles) is many, many dB
less than from plane to bird (15,000 miles).
-John
============
Considering that the GPS antenna in aircrafts is mounted on top of
fuselage,
and that its radiation pattern is upward, it seems that a ground jammer
will
have an uphill battle.
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com]On
Behalf Of J. Forster
Sent: Sunday, November 15, 2009 6:28 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] The Demise of LORAN (was Re: Reference
oscillator accuracy)
Or even into MP3 players, iPods, laptops, or cell phones. Then they'd
wander all over the place too. With the latter two hosts, they could even
be controlled remotely and even be fairly powerful. Would you notice
having to recharge your battery a bit more often?
-John
===========
Magnus Danielson wrote:
Chuck,
Chuck Harris wrote:
What makes you think it needs to be CW, and cannot be pulsed and
chirped?
May I roll in a noise jammer into the debate?
Absolutely! They can be extremely power efficient. Raise the noise
floor in the vicinity of the receiver, and it is all done.
Probably the easiest solution would be to take a PN source and use it
to drive a pulser that pulses a chirp oscillator. If you are feeling
really polite, you could put a bandpass filter on the thing to protect
other services.
All it has to do is confuse the receiver enough so that you can't
trust its readings.
Depends on the goal. For some strategies, blackout is the goal, for
some
getting the readings go haywire every once in a while suffice.
Agreed!
My 9V battery suggestion was for a localized blackout device. You only
have to make the receiver question each satellite's signal often enough
for it to rule it out. No way is CW necessary, or even desirable.
As John suggested, someone (say the Chinese) could put these things in
battery operated stuffed animals, and set them up to jam a little bit
now and then. After Xmas, the GPS landscape would be littered with
these
little stealth jammers, and willing supplicants to replace their
batteries.
-Chuck
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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J. Forster wrote:
Or even into MP3 players, iPods, laptops, or cell phones. Then they'd
wander all over the place too. With the latter two hosts, they could even
be controlled remotely and even be fairly powerful. Would you notice
having to recharge your battery a bit more often?
There is one report in which the laptops of ambulances had CPU
frequencies in the neighborhood (1,5 GHz or 1,6 GHz if I recall
correctly) of the GPS band and the GPS receiver lost tracking so they
essentially lost functionality.
Cheers,
Magnus
Francesco Ledda wrote:
Considering that the GPS antenna in aircrafts is mounted on top of fuselage,
and that its radiation pattern is upward, it seems that a ground jammer will
have an uphill battle.
Not all GPS receivers is sitting on flying airplanes. Far from it.
Cheers,
Magnus