Re: UTC Backbone in Europe
W3AB said:
As y'all know, GPS jamming is easy. We need to have an alternative.
How hard is it to jam Loran? Or WWVB, JJY, MSF, and other low frequency
time signals? How about the not so low frequencies?
What are the units of jamming difficulty?
watts per square kilometer?
How would you scale that by the difficulty of building the antenna?
There is an interesting table of radio time stations in Wikipedia's Radio
clock page:
https://en.wikipedia.org/wiki/Radio_clock
I didn't realize how many there are.
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Hal Murray via time-nuts writes:
W3AB said:
As y'all know, GPS jamming is easy. We need to have an alternative.
How hard is it to jam Loran? Or WWVB, JJY, MSF, and other low frequency
time signals? How about the not so low frequencies?
There's no escaping the wavelength:
Hiding a transmitting antenna for 100kHz is very, very hard.
Even the "real" transmitters cheat, and use antennas which pretend to
be capacitors rather than transmission lines.
Amazingly Sweden did build a VLF jammer and tried to hide it.
They built the "RT-02" aka "Frederiksson" "Chayka" (= USSR Loran-C)
jamming system and put fake parabolic antenna on the transmitter
masts, to make it look like a microwave-link.
The only credible source is in swedish:
https://www.fht.nu/fv_bilder_radio_rasandare_rt_02.html
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
More importantly, what is the cost of including 1-2 alternate systems (radio, inertial, or something else) in the same chipset that is being delivered at large scale?
Having alternative systems is not helpful if they are not being used at similar scale to GPS.
In the overall cost equation, expensive jam-resistant signal sources are justified when divided across billions of devices. Similarly, thousands of less expensive sources (eg triangulation of terrestrial short distant broadband signals) is also viable when used by billions of devices.
On Nov 21, 2024, at 14:51, Hal Murray via time-nuts time-nuts@lists.febo.com wrote:
W3AB said:
As y'all know, GPS jamming is easy. We need to have an alternative.
How hard is it to jam Loran? Or WWVB, JJY, MSF, and other low frequency
time signals? How about the not so low frequencies?
What are the units of jamming difficulty?
watts per square kilometer?
How would you scale that by the difficulty of building the antenna?
There is an interesting table of radio time stations in Wikipedia's Radio
clock page:
https://en.wikipedia.org/wiki/Radio_clock
I didn't realize how many there are.
--
These are my opinions. I hate spam.
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Hi Hal,
On 2024-11-21 03:58, Hal Murray via time-nuts wrote:
W3AB said:
As y'all know, GPS jamming is easy. We need to have an alternative.
How hard is it to jam Loran? Or WWVB, JJY, MSF, and other low frequency
time signals? How about the not so low frequencies?
What are the units of jamming difficulty?
watts per square kilometer?
How would you scale that by the difficulty of building the antenna?
Well, signal-structure wise it's not that hard. For wide area it
requires large antennas, so it's hard to hide, but for local area you
can use much smaller setups such as H-field antennas.
Sweden had a top-secret array of LORAN-C / Chayka jammer/spoofer
transmitters with 212 m antenna towers. It has since been declassified.
So, it's been done. Search for "RT-02 Fredriksson" and you find a report
in Swedish.
Cheers,
Magnus
Hi again,
On 2024-11-21 23:37, Poul-Henning Kamp via time-nuts wrote:
Amazingly Sweden did build a VLF jammer and tried to hide it.
They built the "RT-02" aka "Frederiksson" "Chayka" (= USSR Loran-C)
jamming system and put fake parabolic antenna on the transmitter
masts, to make it look like a microwave-link.
The only credible source is in swedish:
https://www.fht.nu/fv_bilder_radio_rasandare_rt_02.html
This source is not only credible, but I know several of the people who
wrote it, and one of them was responsible for it during it's operation.
He initiated that material was declassified such that this public report
could be written. The introduction shows that it was reviewed rigorously
to ensure it did not contain any classified information. Back in the
day, it was operated intentionally so it would not look like a military
installation, so it was forbidden to drive up to the stations in any
military vehicle. It was operated by Televerket Radio for all what
people saw. Then again, information leaked from espionage, this is
known. Exactly how much it was considered is another thing. You get to
enjoy seeing the classification stamping on the material too.
As people ask about using LORAN-C I need to inform them about these
things. Yes, these towers are far from discrete, but it has been done.
Cheers,
Magnus
Hi
Something like this is designed to take out a Loran (or similar :) :) :) ) system over a large area (like an entire country).
To “mess things up” for a timing system, you don’t need to take things out over an entire country. You likely know exactly where the timing hubs you are after are. All you need to do is mess things up in the vicinity of that building. For Loran or for GPS, it does not take a lot to do that.
The era of broadband jamming seems to be long gone. The approach for decades has been to “spoof” the system and get your result that way. Loran or GPS, the system is not delivering megawatts to your receiver. Unless the Loran is in your back yard (yes that might be the case :) ), you will be well below the milliwatt level … A near field setup is all you need.
Bob
On Nov 24, 2024, at 11:14 AM, Magnus Danielson via time-nuts time-nuts@lists.febo.com wrote:
Hi again,
On 2024-11-21 23:37, Poul-Henning Kamp via time-nuts wrote:
Amazingly Sweden did build a VLF jammer and tried to hide it.
They built the "RT-02" aka "Frederiksson" "Chayka" (= USSR Loran-C)
jamming system and put fake parabolic antenna on the transmitter
masts, to make it look like a microwave-link.
The only credible source is in swedish:
https://www.fht.nu/fv_bilder_radio_rasandare_rt_02.html
This source is not only credible, but I know several of the people who wrote it, and one of them was responsible for it during it's operation. He initiated that material was declassified such that this public report could be written. The introduction shows that it was reviewed rigorously to ensure it did not contain any classified information. Back in the day, it was operated intentionally so it would not look like a military installation, so it was forbidden to drive up to the stations in any military vehicle. It was operated by Televerket Radio for all what people saw. Then again, information leaked from espionage, this is known. Exactly how much it was considered is another thing. You get to enjoy seeing the classification stamping on the material too.
As people ask about using LORAN-C I need to inform them about these things. Yes, these towers are far from discrete, but it has been done.
Cheers,
Magnus
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Magnus Danielson via time-nuts writes:
This source is not only credible, but I know several of the people who
wrote it, and one of them was responsible for it during it's operation.
So how did they know (how well) it worked ?
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
Hi,
On 2024-11-25 15:32, Poul-Henning Kamp wrote:
Magnus Danielson via time-nuts writes:
This source is not only credible, but I know several of the people who
wrote it, and one of them was responsible for it during it's operation.
So how did they know (how well) it worked ?
The receivers where not all that complex. It's a Time Of Arrival (TOA)
approach, so earlier signals messes with receivers. Modern receivers
would be able to filter things out. The one solution to counter it was
to use IMS.
Cheers,
Magnus
On 11/25/24 08:29, Bob Camp via time-nuts wrote:
Hi
Something like this is designed to take out a Loran (or similar :) :) :) ) system over a large area (like an entire country).
To “mess things up” for a timing system, you don’t need to take things out over an entire country. You likely know exactly where the timing hubs you are after are. All you need to do is mess things up in the vicinity of that building. For Loran or for GPS, it does not take a lot to do that.
The era of broadband jamming seems to be long gone. The approach for decades has been to “spoof” the system and get your result that way. Loran or GPS, the system is not delivering megawatts to your receiver. Unless the Loran is in your back yard (yes that might be the case :) ), you will be well below the milliwatt level … A near field setup is all you need.
For systems with generally high field strength at low frequencies, e.g. LORAN-C, you either need a lot of power into efficient antennas, or you need to be very close. You are not going to jam an aircraft LORAN-C receiver from the ground unless you have a fair amount of power and an efficient (large!) antenna. You are not going to be very stealthy. Likewise your adversary is likely to have something to say about you walking up to their receiving site with your jammer.
These characteristics make jamming something like LORAN-C much more difficult than jamming current GNSS systems. That is not to say that you can't, just that it is a LOT more difficult and a LOT less stealthy.
--
Brian Lloyd
706 Flightline
Spring Branch, TX 78070
brian@lloyd.aero
+1.210.620.0011
Bob Camp via time-nuts writes:
The era of broadband jamming seems to be long gone. The approach for decades has been to “spoof” the system [...]
While true, it is still pretty damn hard to transmit 77.5-100kHz
very far without a physically significant antenna, and you can
forget everything about any directivity of any transmitting antenna
you might use.
Furthermore, you can literally pinpoint any VLF transmitter
with just a ferrite rod, a diode and a crystal ear-piece.
You do not even need a tuned filter when you get close enough.
KiloHertz are not perfect, far from, but they are /so/ much more
resilient than GigaHertz.
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.