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What is the difference between a Non-Directional Beacon and a Compass Locator Beacon?

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Normally "Compass Locator Beacons" were co-located with the outer marker for ILS approaches. A "compass locator beacon" is an NDB beacon specifically to drive the radio compass.

A radio compass was a lot simpler instrument than the ADF that worked off of the NDB beacons. Typically it just had a needle that pointed left/right to direct the pilot to turn towards the station. They operate on the same frequencies as ADF/NDB and can be tuned with an ADF receiver.

Radio compasses used the old "loop antennas" that you see on old aircraft pictures. The pilot, co-pilot, or navigator would rotate the antenna by hand (the older radio navigation system required the pilot to turn, so rotating antennas were a step up) to be able to find the bearing to a particular station.

ADF (the "automatic" part of the "automatic direction finder) eliminated the need to rotate the antenna to get the direction to the NDB.

So to answer the question, the NDB and the compass locator beacon are technologically the same, it is the equipment in the aircraft that changed.

See NDB Nav History for more details

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  • $\begingroup$ Ah okay, so a compass locator is kind of like one of those handheld antennas that they (used to?) use to locate ELT signals. It didn't point, it just tippled left, right, or would center if you faced the right direction. Is that how that "Compass locator" instrument works? I have never seen one before. $\endgroup$
    – Ryan Mortensen
    Commented Apr 20, 2019 at 4:36
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    $\begingroup$ That's pretty much right. There is a picture of one in the link at the bottom of my answer if you're curious what they look like. $\endgroup$
    – Ron Beyer
    Commented Apr 20, 2019 at 4:38
  • $\begingroup$ As far as differences go, Locators generally use lower power for the transmission. Also, by way of info, it was not uncommon to have another locator coincident with the ILS 'middle marker' which was typically around the 200ft ILS Cat1 minimums thus indicating passage past the Decision Altitude. $\endgroup$
    – skipper44
    Commented Dec 13, 2020 at 7:40

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