[time-nuts] Re: UTC Backbone in Europe

[Brian Lloyd]

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.

--

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Brian Lloyd
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