Lodestone III - Model 758D MFDF
Equipment nameplate. (Instruction manual image)
The 'Lodestone III and IV' direction finders are very similar in appearance and are both contained in a sheet metal case of pleasing appearance, with the goniometer centrally mounted on the sloping front panel. The units are arranged for bench mounting and the 'Lodestone IV' differs from the model 'Lodestone Ill', in that facilities are incorporated for coupling to a gyro compass so that the true and relative bearings are shown simultaneously on a single scale by means of two separate cursors.

On both models, the degree scale and tuning scale are of comparatively large diameter and uniformly illuminated internally to facilitate precision and ease of reading. Two types of Bellini-Tosi fixed loop aerials are normally employed with this equipment, namely type 354N52 (tall pedestal) or type 354NA52 (short pedestal).

The 758 also had the designator of ND101.

758 Brief Specifications
758 Loop Antenna Photos

Lodestone III - 758D. Range- 250 to 550 KHz. (Instruction manual photo)

Contributors and Credits:

1) Lodestone III & IV Instruction Manual published by Marconi International Marine, The Marconi International Marine Company Ltd. Marconi House, Chemsford, Essex, UK.
2) http://www.rnmuseumradarandcommunications2006.org.uk/MERCHANT%20SHIPS%20AND%20RFA%20FITS.pdf

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Oct 14/12