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# Regarding the L3 frequency

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Posts: 6
Member
(@zyx)
5+ posts
Joined: 1 year ago

If my rover has L1, L2 and L3 abilities and I catch a signal from an modern sattelite with all that frequencies what happens is:

1) my rover will use the three frequencies at same time;

2) my rover will use only L1 and L3.

Any of this statements are correct? Where can I found tesies, pappers about that in particular?

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9 Replies
Member
(@geeoddmike)
Joined: 10 years ago

1,000+ posts
Posts: 1100

FWIW,

There is an L3 frequency. It is 1381.05 MHz and is used as part of  NUDET. Not much good for navigation. You will notice that its frequency as well as L1, L2 and L5 are multiples of the fundamental frequency 10.23 MHz.

BTW, NUDET stands for nuclear detection.

Posts: 23
Member
(@jeran-hopfe)
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Joined: 2 years ago

The frequency is actually called “L5” and is being brought online as a safety frequency for planes, ships, and other things.  It likely depends on your software, but it should use all three.  I can’t see any benefit to only using two.  More frequencies = more measurements to the satellites = higher accuracy.

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(@paul-in-pa)
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Depends on the quality of your receiver. An older style L1/L2 receiver may be more precise than a newer receiver built on the cheap. A precise L1/L2 position requires a receiver to use complicated algorithms to solve L1 and then solve L2. The C/A/C1 code on L1 allows a quick L1 position, the C2 code require more complicated mathematics. The new C5 code on L5 allows for a quick solution on the L5 signals. A new cheap L1/L5 reciver simply means out those two quick positions and gives a better position but all he complicated signal to signal verification is avoided. An L1/L2/L5 reciever most likely has the higher grade mathematics, correlating 1 to 2, 1 to 5 and 2 to 5 thus making a very precise position. Since the L5 signal is stronger you also may be seeing L5 only receivers in the future.

There is no single paper that covers all types of receivers, and manufacturers may be exaggerating the capabilities. First question to ask is how many channels are in the receiver and can you reallocate some to improve the performance?

More frequencies received does not improve accuracy if the frequency differences cannot be used effectively.

Paul in PA

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Member
(@bill93)
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Joined: 10 years ago

It will depend on your hardware as much as the software.  Newer gear is probably adding it but I don't think it will be a retrofit.  Replacement satellites in the last few years have been equipped with L5 but there are a lot up there that don't have it.

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(@gms)
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Posted by: Jeran Hopfe

The frequency is actually called “L5” and is being brought online as a safety frequency for planes, ships, and other things.  It likely depends on your software, but it should use all three.  I can’t see any benefit to only using two.  More frequencies = more measurements to the satellites = higher accuracy.

Actually, L5 and L3 are completely different.  GLN is deploying L3OC at 1202.025 and the US L5 is at 1176.45.

Their structured is quite different, plus GLN was started at FDMA while other constellations started as CDMA, but part of the GLN modernization is to provide signals CDMA.

The labyrinth of GNSS signals is still a bit of a moving target. keeping up can be a lot of fun (and/or frustration).

A handy summary is from NovAtel.

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