What's this?

A video:


It seems as though there's a choice of compass, prismatic or lensatic.
 
Non Directional Beacons use the MF band

"NDBs typically operate in the frequency range from 190 kHz to 535 kHz (although they are allocated frequencies from 190 to 1750 kHz) and transmit a carrier modulated by either 400 or 1020 Hz. "

That's the bunny. The ADF loop was manually rotated in early direction finders to find the strongest signal and thus the bearing, although you would have a choice of two, 180 deg apart until you played about with the null and worked out which was the correct one.

ETA: Someone's got the actual device already. Well done.
 

sunny james

Old-Salt
Thanks to all for your excellent and expeditious replies.
The device was given to a friend who runs a 'show and tell' stall who is often gifted with odd items. No doubt we will employ the services of the Arrse Detective Collective again.
 

endure

GCM
That's the bunny. The ADF loop was manually rotated in early direction finders to find the strongest signal and thus the bearing, although you would have a choice of two, 180 deg apart until you played about with the null and worked out which was the correct one.

ETA: Someone's got the actual device already. Well done.
If you had two loops set at 90 degrees you could hook them up to an automatic direction finder that would do all the hard work for you.

marconi-direction-finder-antenna-frequency-brass-nautical-maritime-reverse-view-reg.jpg


FPR-Lodestar.jpg
 
Gurgle says...

NDBs typically operate in the frequency range from 190 kHz to 535 kHz (although they are allocated frequencies from 190 to 1750 kHz) and transmit a carrier modulated by either 400 or 1020 Hz.
 
Post #14 but the object in question is a marine DF and 410Khz is specifically designated as a marine DF frequency so it's strange that it's not covered unless it's a yank thing. They do tend to do things differently.
Photos in the links show the British manufacturer's label.

For me, the curious thing is the inclusion of the morse code, particularly as it's sited at the "idiot" end of the device. Perhaps it's nothing more than having a blank space to fill with something that may come in handy.
 
Point taken but the compass could be in their possession without them realising it was linked.
Curiously, the links show the gucchi illuminable prismatic compass and a lensatic compass. I suspect that the lensatic compass is a jury rig following breakage of the original equipment.

I dont know how the lensatic would have compensated for the magnetic fields that must have been flying around inside the box.
 

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