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I see this symbol on an IFR low chart, can someone tell me what it is? IFR chart

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    $\begingroup$ Does the symbol have an associated name depicted? Or if you right-click the area on Skyvector, can you see the name? Look that name up in the FAA's 8260-2 database and it should tell you all you need to know. $\endgroup$
    – randomhead
    Oct 1, 2021 at 4:57
  • $\begingroup$ This symbol appears, e.g. on enroute charts. What puzzles me is you were not able to find it on the chart legend. $\endgroup$
    – mins
    Oct 1, 2021 at 13:43

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More context would be better. The screenshot you posted indicates that there is a navaid information box above and to the left of the symbol, but you cut it off so we cannot see what it says. If we knew the name of the navaid we could search for it in the 8260-2 database and we would know more about it.

But just the symbol itself is enough to know exactly what it represents (which is the point of there being a symbol at all, of course). As TomMcW pointed out, everything you need to know about the charts can be found in the Chart User's Guide. However, it is not a Compass Locator Beacon but rather a Non-Directional Beacon. (A compass locator is a specific use case of an NDB.)

We can see the difference in the two symbols when they are side-by-side:

enter image description here
Left: CLB; Right: NDB

A Compass Locator Beacon has two layers of larger and darker brown dots surrounding its central circle, while a normal NDB has four layers of smaller and lighter brown dots. The image you posted clearly depicts an NDB and not a CLB.

You will find CLBs associated with instrument landing systems, as Tom said. NDBs may also be depicted as the outer marker of an ILS, but they can also appear elsewhere, for example on an airport proper.

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  • $\begingroup$ On the US low enroute charts, NDB and locator have the same appearance. However in the OP there is a North arrow, which seems to indicate a NDB. Why is there a North arrow is another question... $\endgroup$
    – mins
    Oct 1, 2021 at 14:04
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    $\begingroup$ @757toga: Good information. So we have the NDB, regular large symbol, then the compass locator (low power but same symbol), then the locator collocated with the a marker/LOM/LMM, (smaller symbol). Do you know when North arrows are used? $\endgroup$
    – mins
    Oct 1, 2021 at 14:50
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    $\begingroup$ @JanHudec: That seems logical, and would match the smaller size of the locator on FAA charts. Still this symbol on enroute charts is a mystery. $\endgroup$
    – mins
    Oct 1, 2021 at 21:50
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    $\begingroup$ @mins I understand that symbol as NDB (there is frequency 350 given for it), which happens to be co-located with a marker beacon, but that is not really relevant for en-route navigation. It might be smaller because of graphical considerations even. I am somewhat surprised they bothered with the ILS at all (it does not have all or even most ILS). $\endgroup$
    – Jan Hudec
    Oct 2, 2021 at 14:47
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    $\begingroup$ @JanHudec: After searching a bit on compass locator, I have clarified a locator is just a certain category of NDB (class L, 15NM range, other classes are MH, H, HH), used specifically for collocation with an ILS marker. As a NDB is has an individual frequency and identification morse code associated. There name comes from ADF predecessor: radio compass. $\endgroup$
    – mins
    Oct 2, 2021 at 17:16
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It is a compass locator beacon1. It’s an NDB located at the outer marker of an ILS. Despite the name it has nothing to do with a compass. According to ARGOTI it is called that because the name “actually comes from the old radio compasses installed on airplanes.”

1 From FAA Aeronautical Chart User’s Guide pg. 70.

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  • $\begingroup$ Could also be used as a LMM (locator middle marker) vs LOM (locator outer marker). $\endgroup$
    – 757toga
    Oct 1, 2021 at 0:40
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    $\begingroup$ Why do you think it’s a locator rather than an NDB? $\endgroup$
    – StephenS
    Oct 1, 2021 at 1:05
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    $\begingroup$ It is not a compass locator beacon. Compass locator beacons have a two-layer circle of brown dots around the central circle; OP's icon has a four-layer circle of brown dots, indicating that is an NDB. $\endgroup$
    – randomhead
    Oct 1, 2021 at 4:56
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    $\begingroup$ @zachinquarantine Please accept the other answer. I have misidentified the symbol. $\endgroup$
    – TomMcW
    Oct 2, 2021 at 2:21

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