FR-12  Transmitter-Receiver

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The Canadian Marconi FR-12 transmitter-receiver was, as explained in the operating manual, "designed for operation on marine frequencies on small ships, notably fishing vessels". That might have been Marconi's intended market but after the outbreak of World War II in 1939 ,it appears to have been adopted by the Royal Canadian Navy as standard equipment for the large numbers of new vessels soon to be coming out of the builder's yards. It fulfilled the communications role for small coastal patrol vessels and supplemented more powerful long-range equipment installed on ocean-going ships

During WWII, the FR-12 was a mainstay on many RCN vessels and was used on CW for inter-communication between escort ships on convoy runs. Voice was available but rarely used.  The popularity of the FR-12 dropped when the TBS transmitter/receiver was introduced into service.  On low wave band, the set had a range of about 20 miles.

In a peacetime navy,  the FR-12 was used to communicate with merchant ships or the Naval Administrative Net (at sea). Pictures taken in the 1950's show the handset installed, so it was definitely used on voice. Emergency communications could be provided by the FR-12 since it only operated from a 12 volt DC power source. The receiver section consisted of a five tube superheterodyne design with the ability to continuously tune the range of 375 to 4200 KHz in three bands. To simplify the overall design, there was no direct frequency readout for the receiver. Instead, a circular logging scale dial was provided. It was necessary to calibrate the dial, and record the readings in advance.

The transmitter section had an oscillator, a modulator and a dual power output stage. One of four, selectable, internally mounted crystals determined the operating frequency. In order to activate the modulator, one simply inserted the handset plug into the front panel socket. The microphone in the handset provided the interlock for the modulator. If this was done while the Dynamotor was running, a noticeable slow down of the Dynamotor could be heard.

Power for the FR-12 could be provided by one of two modes. In standby mode, the filament circuit for the transmitting tubes gets disabled. Filament power for the receiver would be provided from the main battery. The 180 volt B+ line for the receiver would be furnished from four, external, 45 volt dry batteries wired in series. Standby mode would dramatically increase the life of the main battery. In normal mode, all power for the receiver and transmitter was provided by the main battery. An internal Dynamotor produced high tension for the transmitter but it had to be inspected after every 500 hours of operation. Input power to the FR-12 was 12 volts DC at 6 amps on receive and 13 amps on transmit when used in normal mode.

Al Goodwin of Dartmouth N.S. did some range experiments with the FR-12. "It was sent away in a sea boat on a couple of occasions. In those days, we didn't have commercial mobile antennas available to us, so we rigged up a 35 foot whip antenna. The exercise was not deemed a success as we lost communications around five miles. On HMCS HAIDA, we used this set for both AM and CW communications. For CW operation, we would have to attach a key with a very long lead. In an unusual case, the late Keith Lake (VE1PX) used the FR-12 to modulate the Marconi PV500 transmitter thus giving it AM capability for use on the amateur bands. He put out quite a strong signal compared to the 30 watts of the Marconi CM11".

Normally the FR-12 would have a feedthrough insulator in the upper left hand corner. The RCN modified these sets by replacing the feedthrough with an SO-239 receptacle so the antenna could be fed with a co-axial transmission line instead of antenna trunking. This example is fitted in HMCS HAIDA.  (Photo by Jerry Proc)

SPECIFICATIONS:

Types: FR-12 (12 volt) #85161-T
             FR-12 (32 volt) #85135-T

Modes: CW, MCW and Voice
Frequency Coverage: LF/MF  - 375 to 580 KHz (transmit)
                                      HF        -1580 to 4200 KHz    (transmit)
                                      MF Receive only  - 550 to 1600 KHz
MCW oscillator  1,000 Hz
Power Input: 15 watts on CW, less on MCW and even less on voice.
Power input:  12.6 VDC @ 6 amps or 32 VDC
Frequency Control: Four crystal controlled frequencies.
Receiver IF: 260 KHz
Weight: 69 lbs.
Duty cycle: 5 minutes transmit followed by 5 minutes receive, otherwise the Dynamotor will overheat.
CIrca: February 1942 as dated in the manual.
RCN Ref. Number: 5820-21-041-1615

The following  standard crystal frequencies were available for the FR12:

391.5 KHz  - Usage ?
425 KHz - Port wave
500 KHz -  Distress
1630 KHz  - Unique Canadian west coast maritime mobile working frequency..

Crystal case style is ' BY'

Above and below: This pristine and unmodified example of the FR-12 is owned by Meir Ben-Dror  WF2U. Note the RF feedthrough insulator with wing nut to the left of the meter. (Photos by Meir Ben-Dror)

FR-12 - top view of chassis. (Image courtesy Canadian Marconi)

Another example  of the FR-12 chassis top view. (Photo by Jerry Proc)

FR-12 - bottom view of chassis.  (Photo by Jerry Proc)

This is the AC operated power supply for the FR12. It came in either a 12 or 32 volt version. The FR12 could also be operated from an emergency battery source. (Photo by  Alastair Slydell  , VA7COB)

Radioman H. Cook might be sending Morse from the the FR12 in this undated photo. Note the cradle arrangement for the FR12 handset.   He is also using a semi-automatic key (bug( which was not standard RCN issue. Any operator wishing to use a bug would have to provide their own.. If Canadian Marconi was purchasing keys from Signal Electric for the CM-11, it seems reasonable they would go to the same manufacturer for their FR-12. Also, a number of firms made clones of the Signal Electric key, including SpeedX. (Photo credit unknown)

The FR12 being used during the Fraser Valley floods of June 1948. Click on photo to enlarge. (Photo submitted by Tom Brent)

VARIANTS

There were lots of FR12 variants based on mains voltage and crystal combinations.   The  following mix of LF/MF and HF channels could be ordered from Canadian Marconi:

85161  FR-12 (12 volt)
85135  FR-12 (32 volt)

85135S   (32V)  Channels 1 and 2 for LF/MF; Channels 3 and 4 for HF
85161S   (12V)  Channels 1 and 2 for LF/MF; Channels 3 and 4 for HF

85135AS (32V)  Channels 1, 2, and 3 for LF/MF; Channel 4 for HF
85161AS (12V)  Channels 1, 2, and 3 for LF/MF; Channel 4 for HF

85135BS (32V)  Channel 1 for LF/MF; Channels 2, 3, and 4 for HF.
85161BS (12V)  Channel 1 for LF/MF; Channels 2, 3, and 4 for HF.

A  -H in the model number indicates that the remote control option was installed. The manual does not do a good job in explaining the variants. In the back of the manual there is a hand written note indicating PH , TH and BRA variants.

• PH = FR-12P with remote control option, 2LF and 2 HF crystal positions
• TH = FR-12T with remote control option, 2 LF and 2 HF crystal positions
• BRA = FR-12R, 1 LF and  3 HF crystal positions (meaning of "A" unknown.( Maybe its an error)

Besides power supply and crystal variants, there are  three different methods  of feeding  the RF from the output  stage to the transmission line. This is another area that is poorly documented in the manual. Early units had the RF feedthrough mounted atop  the cabinet . This design required a spring contact mechanism that completed the circuit from the RF ammeter output terminal to the antenna insulator when the FR-12 chassis was inserted into the case. FR-12s from 1944 onwards had the antenna insulator mounted in the top left corner of the front panel, only an inch or two away from the RF ammeter terminal it needed to connect with. This resulted in a simpler design, possibly eliminating problems associated with the spring contact mechanism. However, there are three historical photos which show the antenna insulator installed to the right of the RF ammeter.

From the manual  "The antenna should be connected to the insulator projecting through the top of the cabinet .The chassis will then slide out, with the antenna connection to the chassis being made by a spring contact which breaks automatically when the unit is withdrawn". No such example has been seen thus far.  Some existing photos show no feedthrough insulator on the front panel or the top of the cabinet. It is then presumed that the RF exits the cabinet by some other  method which has yet to be discovered.

The nodel CD-12 was the Canaduan Army version of the FR12. It had a sping loaded binding post for RF output  and  it was situated to the left of the RF ammeter.

	Note the position of the feed through insulator in this example. The insulator is to the right of the RF ammeter.  In the upper right cormer,  it is susprcted that this component is a round-case crystal. . This FR12 was fitted in the vessel RCMP Irvine in 1950.
	FR-12 in Fairmile Q112. (Photo via James Taylor)  This FR-12 was fitted in Fairmile Q112 while still at the builder's yard. This example appears  to have  the  RF output  feedthrough insulator on top of the cabinet.

This FR12 was fitted in the radio room of HMCS Rupert in 1942. Note the absence of any front panel feedthrough insulator for the RF output. . (Public Archives Canada Photo HS-0262-1 submitted by Spud Roscoe)

 

This FR12 was reconditioned by RCA on December 22, 1958. After the FR12 left RCN service, it received some modifications by one of its previous owners. FR-12's were still being reconditioned as late as October 1963 as evidenced by the tag on FR-12   S/N 128 owned by Meir Ben-Dror. (Photo  via Kijji)

CRYSTAL ACCESS

The new and improved FR-12 of 1944 had another feature as shown in the photos below:The crystal access door eliminated the need to remove the chassis from the cabinet although, from the left-hand photo, it appears that lining up and installing a new crystal would be difficult.  Some  of the 1942 production models had a crystal socket mounted on the front panel which would have some advantages over changing crystals through the top mounted access door

With access cover removed,  (Photo by Tom Brent)	With access cover in place.  (Photo by Tom Brent)

This chart, provided by Tom Brent, sums up the FR12 variants nicely.

From the few study examples that are available and the pool of existing photos, radio collector Tom Brent was able to make   the following conclusions:

1. It is likely that all FR-12's were originally painted with a wrinkle finish, any existing examples with flat (semi-gloss) finish were repainted as a part of the reconditioning process many sets underwent in the late 1950's and early 1960's. Originally, wrinkle paint was also applied to the outside of the case and the front wall of the chassis.  The interior of the cabinet was the same colour as the front panel and exterior of the case but was a flat (non-wrinkle) finish.

2. Early FR-12's had the antenna insulator mounted on top of the cabinet and this was connected to the RF ammeter by a spring contact mechanism attached to the ceiling of the cabinet.

3. Many early FR-12's had the antenna connection modified by relocating the antenna insulator to the front panel, on the right-hand side of the RF ammeter. It cannot be determined if this modification was carried out by Canadian Marconi or if it was completed "in the field" by RCN personnel.

4. Some of the early FR-12's were factory supplied with a crystal socket for Channel 4 mounted on the front panel and an additional switch which enabled the filaments of the transmitter tubes to be supplied with power when the set was in standby mode (receiver only operation from external B+ battery supply).

5. In 1944, FR-12's were being supplied from the factory with the antenna insulator installed on the left-hand side of the RF ammeter and a crystal access door in the top of the cabinet, secured with two Dzus butterfly catches.

6. Also in 1944, sets were equipped with an additional relay connected to a Jones socket mounted on the front panel. This relay was likely factory installed but its purpose is unknown at this time.

7. Later sets also have an unknown control located to the left of the key socket and accessed by removing a plug. This may be a switch with a purpose similar to the one mentioned in point 4 above although this still needs to be confirmed.

So what we have now in the way of  FR12 variants :

- Operation on two different mains voltage.
- Four different MF/HF crystal configurations on the chassis.
- One crystal socket on the front panel for quick change  of frequency.
- Three different positions for the RF feedthrough insulator.
- Offset lettering for the remote control socket.
- With and without crystal access plate atop the cabinet ,
 

This FR12 example is owned by Tom Brent and refurbished by Gerry O'hara. It serves to illustrate the front panel crystal socket and the RF feedthrough insulator to the right of the RF ammeter just like the example aboard RCMP Irvine. The RED and  CLEAR  indicator lamps are not original to the FR12. The original lamps were intended to illuminate the two large black knobs. Click on image to enlarge.  (Photo by Gerry O'hara)

Because there are so few surviving examples of the FR12, it is difficult to collect serial numbers. Here is what we have so far:

Type FR-12-TH   Spec. 103-851  Serial 310   Manufactured 1942 (Owner:Tom Brent)
Type FR-12-PH   Spec. 122904   Serial 581   Manufactured 1944 ( Owner: SPARC Museum)
Type FR-12-PH   Spec  ?             Serial 582    on case: Serial 398 on chassis (HMCS HAIDA).
Type FR12-P       Spec 107-803    Serial 128   (Meir WF2U)
 

The following  FR12 documentation is available for download:

The nameplate on the dynamotor made by Robbins & Myers indicates an output voltage of 350 VDC at 225 ma.

The following standard RCN crystal frequencies were available for the FR12 transmitter/receiver.(High frequency)
The following standard RCN crystal frequencies were available for the FR12 transmitter/receiver.(Low frequency)

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Contributors and Credits:

1) Meir Ben-Dror, WF2U <wf2u(at)ws19ops.com>
2) Marc-André Morin <marc-andre.morin(at)videotron.ca>
3) Tom Brent <navyradiocom(at)gmail.com>
4) Alastair,  VA7COB  <lothlorian(at)shaw.ca>
 
 

Jan 26/22