CM11 Transmitter-ReceiverFirst built in 1942, the CM11 was a transmitter/receiver that was capable of operation in the 375 KHz to 13.5 MHz range. There were two distinct bands of operation: 375 to 515 KHz on low frequency and 1.5 to 13.5 MHz on high frequency. In the high frequency band, the CM11 could be used with crystal or master oscillator frequency control. For low band operation, only the master oscillator could be used. The RCN labelled CM11 crystals with two additional frequencies besides the fundamental - the second harmonic and the third harmonic. On HF, the transmitter could be tuned to operate on any of the three frequencies. Modes and power levels were: CW - 100 watts; MCW - 70 watts; AM - 30 watts. The Signal Electric R63 was the key provided with the CM11 - RCN pattern number 3M/103.
The transmitter chassis is called a TM-11 and the receiver is the familiar CSR-5 . When packaged together as a system, the receiver, transmitter and antenna tuner become the CM-11. If the transmitter and the antenna tuner were sold without the CSR-5 receiver, it would be called a TM-11.
CM11's in service with the RCN were modified to operate with a "Man Aloft" key. This safety feature prevents the final RF stage in the transmitter from being energized in case f someone has to climb the mast to work on the antenna. Generally, the lock was fitted to the cabinet of the CM-11 at the left side near the top. In the example below, it was fitted on the CSR-5 receiver of the leftmost CM11.
Inter-connection between the transmitter, receiver and antenna tuner was provided by snatch plugs and electrical bus. These connectors operate on the same principle as knife switches. Each of the three slide out assemblies in the CM11 are equipped with female snatch plugs. When slid into place, the antenna tuner, transmitter and receiver interconnect through a wiring bus that is fitted with male snatch plugs. The CM11 antenna tuner was a very versatile device, since it could match antennas that were 5 to 750 ohms resistive and supported operation in the range of 375 KHz to 13.8 MHz.
Keith Kennedy ex-C2NET(s) of Surrey BC notes that "the CM11 was notorious for generating harmonics and spurious emissions and HMC Ships would routinely receive harmful interference reports from the Department of Transport monitoring station located at Wetawaskin Alberta. We had little in the way of test equipment and certainly nothing as fancy as a spectrum analyzer so we just followed the CM11 tuning instructions and filed the reports away. The CM11 was also known for its chirpy CW signal when controlled by the master oscillator but it behaved properly under crystal control. CM11's also had a bad habit becoming detuned as the ship rolled. It was the result of changing capacitance between the antenna and the surface of the sea".
Eventually, the CM11 was superseded by the AN/URC32 transceiver in the Royal Canadian Navy.
|This dual CM-11
installation is found in Radio 2 aboard the destroyer HMCS HAIDA. The left
most unit is connected to bare copper transmission line with a quick disconnect
switch mounted on the deckhead. The rightmost CM-11 has a coaxial connector
fitted atop the cabinet and feeds RG-18 coax. Both of the bulkhead mounted
CM-11 speakers are near replicas constructed by Jerry Proc. Below each
CM-11 is the ZM-11 power supply. (Photo by Jerry Proc)
In the 1960's the RCN experimented with tuning adjustments of the CM11. Atop the rightmost CM11 is the experimental E-886 antenna tuner. A replica of this tuner was constructed by Jerry Proc from microfiche supplied by the Canadian Navy. There are no records around to indicate what it is supposed to do .
Frequency Range: LF - 375 to 515 KHz
HF - 1.5 to 13.5 MHz
Modes: CW/MCW/AM . On MCW the note is fixed at 1,000 Hz.
Frequency Control: Crystal or Master oscillator.
RF Power: 100 watts on CW; 70 watts on MCW and 30 watts on voice.
Antenna Impedance: Will match antennas that are 5 to 15 ohms resistive on LF or
15 to 750 ohms resistive on HF.
Primary Power: 115 VAC @ 5.4 amps, 60 Hz or 24 VDC @45 amps.
Weight: 478 pounds including power supply.
Colours: The CM11 is known to have been painted in:
a) a tan , mat finish
b) light, smooth gray enamel.
c) Medium dark, blue-gray crackle finish.
d) light green
|This CM11, held in the collection of Denis Chouinard, shows the light green colour of the TM11 transmitter and antenna tuner modules. (Photo by Denis Chouniard)|
|CM-11, showing major components including dynamotor, starter , remote control and handset. (Image courtesy Canadian Marconi)|
|TM-11 transmitter chassis - top view. (Image courtesy Canadian Marconi)|
|TM-11 transmitter chassis - bottom view. (Image courtesy Canadian Marconi)|
|TM-11 rear view. (Photo by Jerry Proc)|
|TM-11 antenna tuner - top view. (Image courtesy Canadian Marconi)|
|TM-11 antenna tuner - top view. (Photo by Jerry Proc)|
|TM-11 tuner - bottom view. (Image courtesy Canadian Marconi)|
|TM-11 tuner - bottom view. (Photo by Jerry Proc)|
|TM-11 tuner - rear view. (Photo by Jerry Proc)|
|CM11cabinet with all units removed. The silver plated bar, indicated by the arrow, interconnects the anode of the 813 RF output tube to the input of the antenna tuner. (Photo by Jerry Proc)|
|This is the interior view with just the antenna removed. (Photo by Jerry Proc)|
|Detailed view of TM-11 to antenna tuner interconnect strap. The fitting atop the 813 tube connects to one side of the strap, A contact on the tuner mates with the other half of the strap thus interconnecting the tuner to the transmitter.|
The CSR5 receiver used in the CM11 is not included in this web document. Please refer to the CSR5 document in the Equipment listing section of this web page.
The ZM-11 power supply consists of three separate assemblies. From left to right:
1) Transmitter low voltage power supply. #102-902
2) Transmitter high voltage power supply. #102-900
3) Receiver power supply. #102-903
The ZM-11 power supply can operate on 120 VAC or 24 VDC power sources. A 20 second time delay circuit prevents power from being applied to the transmitter in order to protect the mercury vapour rectifiers. There was an emergency mode which decreased the time delay to 4 seconds but at the expense of shorter mercury rectifier life.
|Front view of the ZM-11 power supply showing the three sections. Left unit is the low voltage supply for transmitter. Middle unit is the high voltage supply for the transmitter. At the right is the receiver power supply. That dynamotor is only used when the CM11 is connected to a battery source. It is only capable of powering the receiver. Otherwise, the receiver runs from a 24 volt DC source. (Image courtesy Canadian Marconi)|
|ZM-11 power supply - front view. The gate safety interlock is fitted in the middle power supply. It energizes the transmitter when the cover is in place. When removed, it is necessary to engage the override switch adjacent to the gate switch if power is desired. (Photo by Jerry Proc)|
|ZM11 - top view of low voltage supply for TM-11 chassis. (Image courtesy Canadian Marconi)|
|ZM11 - top view of high voltage supply for TM-11 chassis. (Image courtesy Canadian Marconi)|
|ZM11 - top view of CSR5 power supply. Note the rotary converter for operation on 24 DC power systems. (Image courtesy Canadian Marconi)|
|This is the #122-103 dynamotor for a CM11. It converts 24 VDC to 115 V 60 Hz. Behind it is the starter unit #122-147. The knife switch to the left is the battery charging panel . In one position the battery is connected to the charger. In the other position, the battery is connected to the dynamotor input. (Photo by Jerry Proc)|
The CM11 could be operated in radiotelephone mode by the SM11 remote control unit. An example is shown below.
|The SM-11 remote control unit ( #110-827) could be used with the CM-11 up to 100 feet away but only on radiotelephone. (Image courtesy Canadian Marconi)|
|The official CM-11 speaker. (Photo source unknown)|
|In RCN shipborne applications, the CM-11 needed a "Man Aloft" key. If a radio operator had to climb the mast to work on the antenna, he could disable the transmitter with a key and take it with him. In the left photo, the key has been installed in the frame. At the right, the key is fitted in the front panel of the CM-11. (Photos by Jerry Proc)|
|The lower left area of the CM-11 frame was reserved for a blank antenna tuning chart. Not all CM11 cabinets were fitted with the spare chart feature. (Photo by Meir Ben-Dror WF2U)|
The test cable could be used to troubleshoot either the CSR-5A receiver of the TM-11 transmitter chassis. When used with the TM11-A chassis, one end of the cable plugs into the connector marked "Test Cable Here Only". This label is not in evicence on a TM-11 chassis.
|The lower right area of the CM-11 frame was reserved for the storage of the test cable.(Photo by Jim Brewer)|
|Marconi test cable #114-830, RCN Patt No. 3?/273 close-ups. (All photos in this block by Jim Brewer)|
|RF OUTPUT CONNECTIONS|
|RF output connection to bare wire transmission line using a porcelain feedthru. This may not be an original insulator.||This RG-18 coax fitting has been retrofitted by the RCN.|
|Rear view of the bracket and connector assembly which adapts the CSR-5 receiver to the CM11 cabinet. Just by removing the bracket, the CSR-5 can be converted into a standalone cabinet configuration. The receiver assembly is marked 110-480Z. (Photo by Jerry Proc)|
|The CM-11 used the standard Marconi crystal of the day. (Photo by Jerry Proc)|
|CM11 crystals in their original factory packaging. These are known as type BY crystals. The same crystal type is used in the CSR5 receiver. (Photos via E-bay)|
The following standard RCN crystal frequencies were available for the CM11 transmitter.
CM-11 VERSUS CM11-A DIFFERENCES
There is only one known variant of the CM-11 and that is the 'A' model. Meir Ben Dror, W2FU has identified at least four differences in the table below.
|Relay shield cover added.||An additional trimming capacitor was added in Buffer No. 2 section.|
|Resistor mounted vertically next to the 813 socket.||Type number suffixed with 'A' designator|
|All photos in this table by Meir Ben-Dror, WF2U|
The CM11 manual (Canadian Marconi's version) is available for downloading although it does not include the oversize schematics depicted in Figures 19, 20 and 21. The blank antenna tuning chart is courtesy Meir Ben-Dror WF2U.
|CM11 Manual - Sections 1 to 6|
|CM11 Manual - Sections 7 and 8|
|Antenna Tuning Chart Blank|
|Schematics - See CM11A section|
This documentation has scanned from BRCN 2769 which is the RCN version of the Canadian Marconi CM11 manual. Because some of the Figure drawings in Section 8 are larger that the bed of a normal scanner, they have been scanned separately and some have been split into left and right sections in the interest of printing convenience. After printing, these documents can be taped together and trimmed to reconstitute the original information.
|CM11A Instruction Book BRCN 2769 - Sections 1 to 7|
Book BRCN 2769 -
Section 8 (less oversize dwgs)
|TM-11 Component Identifier - Figure 3 Chassis Top View|
|TM-11 Component Identifier - Figure 4 Chassis Bottom View (Left)|
|TM-11 Component Identifier - Figure 4 Chassis Bottom View (Right)|
|TM-11 Schematic - Figure 22 Left|
|TM-11 Schematic - Figure 22 Right|
|ZM-11 Schematic - Figure 23 Left|
|ZM-11 Schematic - Figure 23 Right|
|CM-11 Internal Cabling Schematic - Figure 24|
|Dave Blais, RCN radioman at the time, adjusts one of the CM-11 transmitters aboard HMCS Restigouche in 1959. (RCN photo from the collection of Dave Blais)|
Contributors and Credits:
1) Keith Kennedy <a4a88300(at)telus.net>
2) Marconi CM11 Operations and Service Manual #122-104 RCN Ref 3X/102
3) Meir Ben-Dror, WF2U <wf2u(at)ws19ops.com>
4) BRCN 2769 Instruction Book for the CM-11A
5) Jim Brewer <firstname.lastname@example.org>
6) Denis Chouinard <denischouinard(at)enter-net.com>
7) Dave Blais <brodger0131(at)rogers.com>