LOCATION : Located on starboard side below the lattice mast.
YEAR OF INSTALLATION : Before 1956. Restored to 1962 configuration on Aug 1, 1993.

CREW COMPLEMENT : 2 - Anyone working in this room would have to be cleared for top security. See PERSONNEL in this section.


This was the electronic warfare room but mostly referred to as simply "Radio 4". It was capable of providing direction finding services in the MF radio bands plus the interception of radar transmissions in the super high frequency (SHF) bands.

For monitoring and recording of tactical radio traffic using a Hammarlund general coverage receiver and tape recorder.

Provided two-way high frequency communications between electronic warfare rooms.

TELEPHONE CONNECTIONS: Connects to Radio 1, the OPS room and the bridge.

Deck plan for Radio 4.

Radio 4 as found. The layer of dust is residue from the sandblasting of 1982. (Photo by Jerry Proc)

Radio 4 after restoration in August 1993. (Photo by Jerry Proc)
Radio 4 in April 2004, after the addition of the AN/SRC-501 mockup to the shelf, top middle . Bottom row (L-R) Webcor reel-to-reel recorder, SP600 general purpose receiver and the Marconi FM12 D/F set. (Photo by Jerry Proc)
According to Cdr. R.A. Willson of Toronto (Ret'd), Radio 4 or its equivalent, depending on the type of ship, was also known as the Electronic Warfare room (EW), Electronic Warfare Control Room (EWCR), EW Shack, or EW Hut depending on the era. In the Fleet or Task Group Communications Plan there would have been an EW Primary communications circuit, EW(P) in the UHF Range and an EW Secondary circuit, EW(SEC), in the MF/HF Range. EW(P) would be used as the control circuit for tactical EW and EW(SEC) used when units were outside UHF range. In Radio 4, the EW(P) circuit was provided via the RCU mounted on the forward bulkhead. EW(SEC) may also have been used as a "yak" circuit if the Radio Silence Policy permitted, since it was not normally monitored in the Ops Room or on the Bridge like the EW(P) circuit.
4.1 - AN/SRC 501 Transceiver 

src501.jpg The AN/SRC-501 was designed primarily for marine installations, and intended for ship-to-ship or ship-to-shore communications over short distances. In the RCN, it was used to provide a secondary communications circuit EW(SEC) between electronic warfare rooms using the high frequency radio band. It was generally used when ships were beyond UHF line of sight range. Radiotelephone transmission and reception used any one of four, crystal controlled frequencies in the 2 to 4 MHz band. Optionally, the receiver section could be continuously tuned for reception in the 0.5 to 1.5 and 1.5 to 4 MHz bands. Twelve watts of power was delivered to an antenna tuning unit in the base of a 19 foot whip mounted on the starboard side of the bridge. The most common fault with the system was moisture leakage into the antenna base due to being exposed to the elements. One former CS rating offered his personal comment about the operation of the AN/SRC 501. "Its main use was an intercom between Radio 4's. A good megaphone was just as good, if not better". (Photo courtesy RCN)

The following standard RCN crystal frequencies  were available for the transmitter portion of the SRC-501.
The following standard RCN crystal frequencies  were available for the receiver portion of the SRC-501.

Hi-res photo of the AN/SRC-501. (Photo # O-15197 courtesy DND, Canadian Forces Joint Imagery Centre provided via by Robert  Langille)
A mockup of the AN/SRC-501 built by Jerry Proc VE3FAB. No real example of this set has ever been found.  (Photo by Jerry Proc)

4.2 - AN/UPD-501 Radar Band D/F Receiver


Robert Langille provides some background material. "The UPD-501 was registered as a JETDS device from 1952 to 1995. During its service life, there were three variants:

* Variant 1 was fitted to the Tribal and Prestonian Class ships. - There were only  X band horns fitted to a plate which sat atop the foremast. 

* Variant 2 saw service on the RCAF's Avenger AS3M, Lancaster MK X, P2V7, Neptune (Temp), CS2F Tracker and also aboard HMCS Bonaventure.

* Variant 3 was applicable to the St Laurent, Annapolis, 280,  and IRE class of ships. It was also found on    Mackenzie and Saskatchewan. Early fits in late 1950's may have been as Variant 2 but later evolved
to include J Band.

EMI Cossor produced the units for the initial procurement. During the 1960's EMI was acquired by Raytheon UK".


A UPD-501 was a High Probability Radar Early Warning directional finding receiver which was used to detect radar emissions on the SHF radar bands and gave some indication of the wavelength in use, bearing, and the antenna rotation period. The receiver was connected to a horn antenna assembly which was mounted on the foremast top and connected to the receiver by RG55/U coax. Initially, the UPD 501 horn antenna (circa 1953) was designed to monitor X band radar only. This was the version fitted on HMCS HAIDA and depicted below.


In the above diagram, 1N23WE diodes located in the antenna housing acted as signal detectors. Changing these diodes could be a very interesting experience in harbour, let alone at sea. In the 1970's, a two band version (X and L) was introduced. Later, the antenna was redesigned for coverage in three radar bands. The multiband version was a two piece, symmetrical unit. Each vertical section was 34 inches long and consisted of four cylindrical antenna modules that were bolted together. The original concept of the "can" enclosure was devised by a RCAF engineer at Shearwater , Nova Scotia while trying to fit the UPD to an Avenger aircraft in 1955.

Click om image to enlarge. 

The three band UPD antenna had the following coverage:

2.3 to 5.5 GHz
5.5 to 10.8 GHz
10.5 to 20 GHz


This is a detailed sketch showing one side of the UPD-501 multiband antenna. (Drawing courtesy RCN)

The design of the UPD501 was simple. In the set itself, there were four, wide-band radio frequency amplifiers, one for each 90 degress of the compass rose. The outputs of the amplifiers would be applied to the four plates of a cathode ray tube and the relative signal strength caused a blip to appear on a CRT. This blip was appropriately deflected to visually indicate the relative bearing of the incoming signal. In the absence of any signal, a spot of light would simply appear in the centre of the CRT. Upon receipt of a radar emission, an audible alarm was also triggered. This alarm could be monitored by a loudspeaker or headphones.

Pat Barnhouse, a former Electrical Officer and Radioman Special aboard HMCS HAIDA outlines a serious problem with the original UPD 501 antenna design and how it was rectified. "Our ship an inoperative UPD 501 set.  It turned out that the crystal detectors in the horns had been burned out as a result of receiving an overload of RF from a nearby high powered radar, probably an SPS 10 or 12 sitting close to us in Halifax harbour.  The problem was that there were no shutters on the original UPD 501 horns to protect the sensitive 1N23 mixer diodes and this burnout problem became endemic. Replacement was compounded by the horn placement on the bottom of that flat plate at the top of the mast extension, requiring a dockyard crane to effect replacement.  The later multiband versions of the 501 came with the antennas mounted in "cans" that had shutters over the horn mouths. There was only one drawback to the UPD501 - it could not be used if the ship's own radar was operating. During the 1970ís, the 280 Class ships were introduced with EWIS Equipment and the DPTSA. Both of these units used the UPD 501 as an input sensor until replaced by CANEWS. The UPD501 system was replaced in most HMCS ships when they were retrofitted with CANEWS ( ie AN/SLQ-501) during the 1980ís. Most schedule retrofits were completed by 1989/1990. CPF and new city class FFH ships were never fitted with the UPD system they were scheduled to be fitted with CANEWS. (Image courtesy RCN)

This X-band horn has been extracted from the AT-5007 "slice" of the UPD-501 multi-band antenna. The portion in the center and left  is a motor-operated shutter which when closed,  would protect the signal diode against unwanted RF energy. (Photo by Jerry Proc).

UPD-501 receiver aboard HMCS HAIDA.  (Photo by Jerry Proc)
UPD-501 Power Supply (Photo by Jerry Proc)

Curt Bowles, VE3ZN, relates one experience that he had with the UPD-501. " I commissioned HMCS Athabaskan 282 . In those days I had moved from Comms to Electronic Warfare (EW) as it became an official trade and formally manned by CS rates.  In those days were  still operator-maintainers. The EWCR (Electronic Equipment Control Room) didn't have all the equipment up and running when the ship was  commissioned. So as techs, we were involved in setting up the EW Equipment.  We had a pair of UPD-501s plus their antennas that were very sick and parts were hard to come by.

I was a licensed ham as well (VE1AYE) and often we would go down to Junky-Jimís (a  scrapyard just outside of Halifax) in search of  electronic equipment including the Navyís or bits and pieces that could be used for Ham Radio. On one of my trips I found four scrapped UPD-501ís and  their antennas. Needless to say I picked them up for a few bucks and brought them back to the ship and was able to retrofit the existing UPDís and antennas on Athabee. I managed to get them back in working orderÖ I still laugh about that event."

4.3 - FM12 MF/DF Receiver

Designed by Marconi in 1942, this was a tuned radio frequency, direction finding receiver with an frequency range of 42 to 1060 kc and required 220 VAC input power. The FM12 was considered to be a D/F 'outfit' or system and it incorporated the Model FMB receiver. In 1943, the outfit was re-designed for use in submarines and was known as the FM11 which incorporated the FMA receiver. On HAIDA, input power was supplied by a 120 to 220 step up transformer. Power consumption was 60 watts. A directional, fixed frame antenna, was mounted over the wheelhouse and was connected to the FM12 inputs via dual connector blocks and RG57 coax. The STB INNER VERTICAL was the 'sense' antenna for the FM12 and Marconi recommended that the aerial be 30 to 40 feet in length. A wall mounted, gyro repeater provided reference bearings for the operator.

The FM12 was a very good direction finding set for its day. In taking a bearing, the use of the multi-purpose switch was very important. An operator would first tune in the signal of the target station with the Aerial switch in the search position. Then, with the switch in loops, a minimum strength on the outside compass scale of the goniometer was found. Lastly, the operator would place the Aerial switch in the sense position and would rotate the goniometer slowly clockwise. If the signal faded away, the minimum position was the true bearing. Had the signal risen, it indicated a reciprocal bearing and true bearing would be found 180 degrees on the opposite side of the scale.

This unit was originally fitted in Radio 1, however, Jack Raine of Vancouver states that in the '43 to '44 period, the FM12 aboard HAIDA was not used for the stated purpose of intercepting enemy radio transmissions. Instead, it was used as a navigational check to aid in operations in the area of Scapa Flow to Russia, Iceland and Spitsbergen. When HAIDA was transferred to the Plymouth Command in 1944, the unit was not used to the best of his knowledge. The FM12 was mainly used for navigational direction finding. On occasion, it would be used to get a MF bearing on a 'target'. This could be another naval vessel, a merchant vessel or any vessel in distress. On Nov 20 1962, the FM12 was moved from Radio 1 to Radio 4. It must have been quite a job as the FM 12 weighs 211 pounds.

The FM-12 as fitted aboard HMCS HAIDA. (Photo by Jerry Proc)
FM-12 loop antenna.  (Photo by Jerry Proc)

4.4 - SP600-JX Receiver

In the late 1950's, the standard EW/HF receiver both ashore and afloat was the SP600. Many Chief Radiomen would give a fair 'price' to have one installed in Radio 1, particularly to copy the fleet broadcast. Eventually, the SP600 was fitted into main radio offices only because the Racal series of receivers were being introduced into EW service and supplementary shore stations. The SP600JX was a twenty tube general coverage receiver made by the Hammarlund Manufacturing Company and provided coverage in the bands of 0.5 to 54 MHz. The J in the model number indicated that MIL spec components were used in the design and the X means that the unit was equipped with crystal control. In Radio 4, the SP600 is connected to the STBD OUTER VERTICAL antenna using RG22/U (95 ohm) coax. Two characteristic features of this receiver were the gold plated tuning capacitor and frequency coverage up to 54 MHz. Both the SP-600J and SP-600JX were used by the RCN. Although both the Radioman BRCN 3037 (1963) and Radioman Special BRCN 3040 (1961) manuals describe the SP-600J, the Radioman Special manual actually shows a photo of the SP-600JX. (RCN photo)

In the late 50's, the EW/HF listening receiver, both ashore and afloat, was the Hammerlund SP600, which was far superior to the Marconi CSR5 series. In fact, many Chief Radiomen would give a fair "price" to rabbit an SP600 into Radio One, particularly for the fleet broadcast, because of its stability and sensitivity. When the SP600 finally did get in to Radio One's, it was because the Racal series were coming into use in EW and supplementary shore radio stations. They were that much better than the Hammerlund.

SP-600 receiver. (Image courtesy Kurrarjong Radio Museum)
4.5 - WEBCOR Tape Recorder

The Webcor recorder can be best described as a suitcase style, reel-to-reel, portable tape recorder, made by Webcor. It was shuttled between Radio 1 and 4 which likely explains why there is no listing of this gear on the electrical diagrams. When stationed in Radio 4, the recorder was connected to the SP600 receiver and was used to monitor CW traffic from Russian Electronic Intelligence Ships (ELNIT) operating on the 4 and 8 MHz bands. These were the famous Russian "fishing trawlers". When HAIDA returned to port, the tapes were sent to Gloucester Ontario for analysis by naval intelligence. In other ships such as SWANSEA, the tape recorder remained fixed.

ABRS Spud Roscoe says that aboard HMCS Swansea, there was no specific procedure to copy the Russians. Therefore, he copied all the traffic he could using a typewriter instead of the tape recorder. He used the 2 mc/s band because Naval Radio Station COVERDALE  had trouble copying the Russian signals. All the hard copy was then sent to Ottawa to the address given in his EW course. The envelope was sealed with wax and  embedded with the ship's stamp.


Between 1948 and 1968, the Electronic Warfare rooms of HMC ships and many naval radio stations were staffed with members of the Communicator Supplementary or Radioman Special Branch. These were not regular radio operators. Rather, they were members of a branch whose duties were considered secret. Originally created as Communicator Supplementary (CS) in 1948, this branch was renamed Radioman Special (RS) in 1960, but the badge had been changed in 1955. It remained RS from 1960 until the amalgamation of the Armed Forces in 1968. Duties of CS/RS operators included the interception and analysis of "opposition" emissions, both radio and radar.

Security at CS/RS training schools was very tight. Trainees were indoctrinated on the political picture and drilled on the sensitive nature of the work. In order to maintain the highest level of secrecy, CS/RS operators were taught to be 'Operator-Maintainers'.

ABRS Spud Roscoe copies a message from the SP600 receiver in the Radio  4 aboard HMCS SWANSEA in January 1961. Note the chain which holds down the typewriter in case of heavy seas. Pictures such as this were forbidden by the RCN. (Photo courtesy Spud Roscoe)

When a CS/RS operator terminated his duties permanently, he went through a "deindoctrination" process which included signing documents relinquishing SECRET 'CODEWORD', TOP SECRET, SECRET, and CONFIDENTIAL knowledge and a promise never to divulge such without clearance from the Minister of National Defence. In 1952, a few CS operators were collected from various stations around the country to take a course in RCM (Radio Countermeasures) and RADCM (Radar Countermeasures) after which they were dispatched to HMC Dockyard, Halifax. These ratings were not allowed to explain their duties, had to be secretive, and couldn't tell anyone the ships they were boarding. (They didn't even know themselves). They were simply not welcome in the dockyard. What most people didn't know was the reason for their presence - to be involved in the Canadian development of the UPD501 and its operational tests.

Ray White, Chief Petty Officer 2nd Class RCN (Retired), was CS rate and provides some comments on one aspect of his service. "During my time in the RCN, there always was a demarcation line between "us", the guys behind the green door, the keepers of the secrets and the spies. We didn't really feel as if we were members of the 'Sparkers' community. When small numbers of the CS branch went to sea in the Radio Warfare specialty, the Sparkers realized that we did indeed have skills that  meshed with theirs. As a group, we had superior Morse Code copying abilities, especially under difficult conditions.  We never had the luxury of asking for repeats, for example, when copying target transmissions.  So we worked harder to get it right. On the other hand, most CS rates were not well-versed in Morse transmitting. As a group, the acquisition of a Sparker's "fist" was just unheard of".

It took almost ten years to convince the captains of vessels to rely on Radar, yet, when the CS/RS personnel showed up aboard ship, they requested that the Radar be shut down because it jammed the 'D/F' and also gave away the position of the ship! It probably took another ten years to reverse this thinking.

In 1953, electronic warfare rooms were also installed in HMCS Huron and Iroquois for operations in the Korean theatre and each had a CS operator (P/O or L/S of a high Trade Group) drafted on board. There is an incident worth relating about secrecy. On HMCS Iroquois, the new CS op was just drafted but not informed about the protocol of a CS being introduced to the CO. The following day, the Commanding Officer was making his rounds of his new ship and told the Executive Officer that he wanted to inspect Radio 4. Upon hearing this, the CS operator refused to let the CO or XO climb the ladder to Radio 4 and immediately dashed up the ladder to padlock the door. Furious, the CO had him thrown off the ship onto the jetty with all his kit. This was three days before sailing time to the Korean war. Next day, a three-ring commander arrived in Halifax and gave the CO his indoctrination, however, the poor CS was never the most popular person in the eyes of the CO ever again.

Since Radio 4 was considered a top security area. The door was labelled with a sign warning one of this fact and it was always kept locked up when not in use. Since access was so restricted, it was also a good place to catch up on lost sleep. This wasn't so bad considering these CS/RS ratings copied CW at 35 WPM in languages such as plain language English, plain language foreign and Kata-Kana ".

Please refer to the Communicator Supplementary and Radioman Special Branch document in the Table of Contents for more information on CS/RS rates.

Credits and References:
1)  Curt Bowles <curt.bowles(at)>

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Jul 22/20