CR-300 Series Receiver

Type: Single conversion, superheterodyne receiver
Also designated Admiralty Patt. M500A
Frequency coverage: 15 KHz to 25 MHz  in eight bands.
IF: Either 575 or 98 KHz depending upon the frequency being received.
Tube lineup:  ARTH2,  DH63,  four KTW61,  X66, 6V6G.
Power input : Using the Type 889 power adapter, the receiver can operate on any of the following voltages.

230 VAC 50 to 60 Hz   60 watts
24 VDC  54 watts
110 VDC 60 watts
220 VDC 60 watts.
The receiver itself can be fed from any external power supply which provides 24 VDC @0.95 amp and 250 VDC @ 60 ma.

Weight -   Receiver 55 lbs
                Power Unit 21 lbs

Dimensions -    Receiver:  18.75" W, 15.5" D, 13.625" H
                        Power Unit: 6.1875" W,  13.25" D, 8.625"H

Manual reference: T 1864
Manufactured between: 1943 and 1946 for CR300/1 series.
Receiver Versions :

CR300/1 - Comes with a 500 KHz crystal calibrator (oscillator). The harmonics of this oscillator correspond with the dial markings and permit pointer accuracy to be checked.

CR300/ 2 - Comes with a 690 KHz crystal calibrator  (oscillator). The harmonics from this oscillator fall on calling frequencies in the marine bands.

Comment: There is something interesting on the cover of the manual for this receiver. It bears both company names, namely "Marconi's Wireless Telegraph Company Ltd" and "The Marconi International Marine Communication Co. Ltd".

They were totally separate companies: MIMCo bought equipment, much of it made by MWTco (later 'The Marconi Co. Ltd'), but MWT also sold the equipment itself - so the 'Atalanta' receiver of MIMCo was also the NS702 of MWT.

CR300 and power unit  photo courtesy Marconi Marine International manual,. 
The CR300 receiver (leftmost) in its natural habitat. This is the  radio room of P & O's DEVANHA call sign GFBR taken in 1957. (From the collection of Don Chapman courtesy Merchant Navy Nostalgia web page) 

Contributors and Credits:

1) CR300 manual courtesy
2) Merchant Navy Nostalgia web page:
3) Shortwave Receivers Past & Present Communications Receivers 1942-1997 by Fred Osterman.
4) Sandy Blaize ebjr37(at)
5) Peter Chadwick <g8on(at)>

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Oct 24/13