|Marconi CR100/7 Communications
The upper tuning dial gives a linear reading of frequency - it rotates as the bandswitch is operated. The larger centre knob below the index scale is a coarse tuning control and the smaller inner knob is a fine control.
The index scale does not permit a direct frequency reading but does allow for accurate logging.
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|Some Notes On The
Marconi CR100 & Variants
According the manual, there are a number of variants to this venerable old set. The initial prototype was designated CR100. This was followed by variants designated CR100/1 through CR100/8. None of the CR100's were ever fitted with S-meters as standard.
The CR100/2 was also called the R.A.F. type R1297 receiver, as it was issued to the Royal Air Force and the other services, except the Navy.
The CR100/4 had an "R.I.S." (Radar Interference Suppressor) control on the upper left corner, to adjust a blanking circuit in the receiver to the repetition rate of the radar on the ship to prevent pulse interference. Most Model 4's were painted blue with white lettering (like my example above).
The small metal panel with a VR54 = CV1054 = EB34 double diode valve and toggle switch next to it, with the panel marked AP56703 (AP= Admiralty Pattern) is a noise limiter circuit and it is a definite identifier that you have the CR100/8. If you also had the R.I.S. knob, it would have been the CR100/7 model.
The CR100/1, /4, /5, /6, /7 and /8 were also called the Admiralty Model B28 receivers. 'Admiralty Pattern B28' was the standard MF/HF receiver on the Royal Navy and Royal Canadian Navy ships in World War II. After the war, they were phased out and usually replaced with the Murphy B40 receivers in the Royal Navy and Royal Australian Navy. However, in the Royal Canadian Navy, from around, 1943 they were phased out and replaced by the Canadian-built Marconi CSR5 receiver.
The receivers are excellent performers considering the state of technology in the late 30's to 40's. My set has absolutely no problems receiving WWV Colorado on 10MHz during daylight hours in London.
Last updated 22nd September 2002