MDF-3 DF Receiver


Frequency Range: 273 to 667 KHz
Use: Marine D/F receiver
Circa: 1935
Comment: The receiver does not have a BFO and speaker like the MDF-5
Variant: MDF-3B but the manual doesn't indicate the difference.


The MDF-3 is essentially a radio Pelorus, that is, it may be used to measure or determine the bearing of a fixed point relative to the ship's heading.

The pedestal assembly houses the receiver proper, the quadrantal error corrector, the goniometer and the batteries.   Bearing indication  is accomplished by reading a dial.

New at the time was the "Zinc Air Cell" filament battery which could power up the filaments for 6 to 8 months on average use before having to be replaced. This battery did not use a charger.  One advantage of the air cell battery was the indefinite storage time.  This meant it could be carried as a spare and stored dry. To activate it , the operator would simply break the seal and fill it with plain water. The D/F set used the Eveready type 600 air cell.

The Loop antenna consisted of two shielded fixed loops at right angles to each other similar to the MDF-5 antenna.

Complete MDF-3 set. (Image courtesy Laval Desbiens via Spectralumni )

mdf3_2.jpg mdf3_3.jpg
The top portion contained the receiver  electronics.  With front panel swung open. 
(Images courtesy Laval Desbiens via Spectralumni )

MDF-3 Operators Manual - PDF (Courtesy Laval Desbiens via Spectralumni) 

Contributors and Credits:

1) Spectralumni
2) Laval Desbiens <desbiens.laval(at)>

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May 16/08