CSR-4  CSR-4A,  CSR-4B and CSR-4D Receivers

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SPECIFICATIONS

Type: 15 tube superheterodyne
Modes: CW/AM
Provision is made for two crystal controlled frequencies for spot working,
Circa: December 1938
Audio power: 5 watts max.
AC power input: 115 VAC; 25 or 60 Hz
DC: 110 ma @ 250V DC; 4.1 amps @ 6 VDC
Weight: 76 pounds
Dimensions:  19" wide x 10,5" high x 16.5" deep

Frequency ranges:

For CSR-4 as read from a  manual extract.
Band 1 - 13 to 30 MHz
Band 2 - 6.6 to 16.5 MHz
Band 3  - 3.15  to  7.5 MHz
Band 4 - 1,55 to 3.5 MHz
Band 5 - 175 to 375 KHz

As read from the CSR-4A dial below:
Band 1  - 13 to 30 MHz
Band 2 -  3.3 to 7.5 MHz (no coverage from 7.5 to 13 MHz. Why would CBC want a receiver with a frequency
coverage that includes the AM broadcast band and leaves out 7.5-13.0 MHz? )
Band 3 -  1.5 to  3.5 MHz
Band 4 -  850 to 1600 KHz
Band 5  - 540 to 1000 KHz

No dial data available for the CSR--4B  or the CSR-4Cat this time
 

CSR-4D

Frequency coverage: 175 KHz to 385 KHz ; 1.5 to 30 MHz

The D model differs from the earlier CSR-4 (no suffix) as follows:

• No provision for emergency battery power is mentioned, nor is the power transformer rated for 25 Hz AC operation.
• The rectifier tube changed to type 5Y4.
• IF frequency is 455 KHz (the 1938 document  procuted a while ago has 575 KHz penciled in as the IF frequency).
• Audio output stage is a single 6K6. The earlier CSR-4 had two 6K6 tubes in a push-pull configuration.
• Paint colour is Marconi battleship gray.
• The top cover is hinged. Earlier examples seem to be lacking hinges,at the top of the case.

The 'differences' information was derived from the CSR-4D manual dated Feb 2/40.
A marketing document along with a technical description can be found here. However , the he CSR-4D schematic is missing. (Provided by Tom Brent)

 
TYPES

CSR-4 receiver in metal cabinet                     75951
Dynamic speaker in cabinet                           80430
CSR-4 rack mounting                                       75950
Dynamic speaker, rack mounting                   75952
CSR-4 receiver, dynamic speaker;
           rack mount with 10.5 in blank panel    75953
 
 

A high res CSR-4 front panel photo. Click on image to enlarge Photographic evidence indicates that  the CSR4 was used by the DOT, the CBC and at the RCN's Gordon Head intercept station.  (Provided by Dave Whiting VA3QG)

A high res CSR-4  top view photo from the manual. Click on image to enlarge. (Provided by Dave Whiting VA3QG)

CSR-4A front view. This example has been beautifully refinished but sadly not in its original Canadian Marconi paint scheme. The original bakelite knobs were replaced with ones of a more contemporary styling. There was no 'S' meter in the original radio. It was added by a previous owner. The black rectangle  is the access hole where two crystals could be plugged in and be selected by the control directly above the hole. Click on image to enlarge.

CSR-4A rear view. The receiver's B+ and filament voltages are provisioned on the leftmost terminal strip, likely to power a device external to the receiver. With this arrangement one had to be mindful of the shock hazard when reaching for the rear of the receiver.  This is likely the original colour of the receiver. Cl Click  on image to enlarge.

At the back of this specific receiver example,  there is a CBC logo affixed. This was the logo used by the CBC from 1940 to 1958. It is believed that this particular radio was used by the CBC Monitoring Service. (Courtesy CBC Radio Canada)

CSR-4A chassis view,  The  mounting board with the two potentiometers and a horizontally mounted tube is likely the driver circuit for the aftermarket  'S" meter, One pot is likely for zeroing the meter, while  the other is for setting full scale deflection. Click on image to enlarge. It was not an original fitting.  At the top middle is the power transformer. At some point the  original transformer failed and the one chosen to replace it had a larger footprint. As a result, the rectifier tube would not fit with the new transformer in place and thus it was moved to a position between two of the filter capacitors.

CSR-4A photos via E-bay.

Tom Brent provides his observations after reading the nformation about the CSR4 which has been collected to date.

1. The information bulletin states the primary purpose of the power connections that are brought out to the terminal strip on the rear of the chassis are for emergency operation on batteries. That doesn’t mean they couldn’t be used to power an external device but at this point we have no evidence of that.

2. I went looking for the “quick change-over switch” that allowed the receiver to run on batteries or AC line voltage. In the high resolution photo that Dave provided, you will see what appears to be a knurled lever located to the left of the 5X4G rectifier tube. Notice it has two slot head screws to either side (above and below in the photo) and the lever grips a shaft with a flat machined into it. I’m quite sure this is the AC/battery switch. The screw spacing (1.5 inch) matches what is found on a standard rotary switch and the shaft profile also jives. Further, if you look at the photo on Jerry’s webpage that shows the rear of the CSR-4A cabinet, you will see a slot in the appropriate location for having the lever sticking out. This would allow the switch to be operated without removing the top cover from the cabinet if it was necessary to quickly change over to emergency power. Presumably, when running on AC power, the switch would disconnect the “hot” terminals at the back of the receiver.

3. There are some oddities in the information bulletin. The section titled “Selectivity Control” actually describes AGC switching and in the circuit description it refers to the oscillator/mixer circuit as “frequency changing rectifier”.

4. The frequency coverage of this (presumably) first model of CSR-4 is 175-375 KHz & 1.55-30.0 MHz with an IF frequency of 575 KHz. That’s a little odd in that it didn’t go higher in the MF range and cover the 500 KHz distress/calling frequency as the CSR-5 did.

5. The CSR-4A model seen on eBay (and Jerry’s webpage) covered 530 KHz – 7.5 MHz and 13.0 – 30.0 MHz. For a reason that will probably remain forever unknown to us, a version of the CSR-4 was needed that would tune the AM broadcasting band while deleting 7.5 – 13.0 MHz coverage. Because it tuned the AM band, the IF frequency of 575 KHz would have been changed, probably to something in the 455 KHz range.

6. In addition to the SEND/RECEIVE switch that controlled plate voltage to the RF and  IF tubes, there was also a T/R relay which could be controlled by the transmitter.

7. The information bulletin is dated 21 December 1938  adds to the timeline we have slowly developing for the entire Canadian Marconi CSR receiver series.
 

February 1942: An intercept operator at Hartlen Point, N.S. is using a Canadian Marconi CSR-4 receiver. At the left side is a Hammarlund receiver most likely  the SP-200. (Photo submitted by Laval Desbiens VE2QM)

CSR-4 at Digby Island, BC.  It's located second from the right at the bottom of the rack.( Photo provided by Dave Whiting,  VA3QG)

CSR-4 at Digby Island, BC It's located second from the right at the bottom of the rack.(Photo provided by Dave Whiting,  VA3QG)

CSR-4B at station VAU. (Photo credit - Dr. H . B . Sabean)

CBC MONITORING SERVICE

At this point, the suggestion that the CSR-4 was in the service of the CBC Monitoring Service rests solely on evidence provided by the CBC logo stuck on the back of the cabinet. The period of use (1940 to 1958) for that particular logo is commensurate with when a CSR-4 might have been in service with the CBC. What is needed are some photos.

A United States Department of Commerce publication provides a bit of background information. Established in 1935 on 18.5 acres of land in Britannia Heights (west end of Ottawa), the HF monitoring station was used for technical monitoring, i.e., reception information exchanges with various broadcasting organizations directing transmissions to North America. It was also used for program monitoring for information and/or pickup for rebroadcast on domestic CBC networks. For example, BBC News, certain ORTF (Paris) programs, etc. This role would have been very active during World War II when the BBC would relay program material created by CBC reporters who were accompanying Canadian troops in Europe.

From the middle 1960’s on, there were increasing levels of local electrical noise due to a new highway within feet of one of the antenna systems at the Britannia site and encroachment of local dwellings. Antenna systems at this time included at least 2 rhombics. When it became known in the late 1960’s that adjacent land would be developed for single family housing units and City of Ottawa wished to build a high school on part of the monitoring station property, a decision was made to relocate. In 1972, the monitoring station moved to a 40 acre site in Stittsville (or possibly Carp). Receiving equipment made by TMC, Mullard, Racal and Plessey was used at the new site. Antennas included a Collins rotary log periodic, Hermes aperiodic loop arrays, Beveridge and Telefunken Omni-Pole.

So, this was not a small back-room operation and it will not be surprising if we learn they had multiple CSR-4’s as well as other types.

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Contributors and Credits:

1) Laval Desbiens <desbienslaval(at)gmail.com>
2) Spud Roscoe <spudroscoe(at)eastlink.ca> Deceased as of Dec 20/23
3) Arthur Crowell  <af(at)ns.sympatico.ca>
4) Gerry O'Hara
5) Dave Whiting  VA3QG  <Barbar3380(at)outlook.com>

May 2/24