Tour of CFRB/CFRX Transmitter Site (new images)	CFRB Coverage
CFRB Web Site	CFRB/CFRX Reception Reports

CFRB (1010 kHz), began broadcasting in 1927. The original transmitter site was at Aurora, Ontario, and the approximate power was 15 kW. Tubes used in the first transmitters were manufactured by the Rogers vacuum tube company. Indeed, the name of the radio station reflects the Rogers involvement in radio broadcasting, "Canada's First Rogers Batteryless".

In 1946, a new transmitter site was opened at Clarkson, Ontario (the present site), and was the first 50 kW DA-2 array in the British Commonwealth. The array was four 250' towers, fed by open-wire transmission lines from the phasing system within the main building. The transmitters were by RCA, a BT50-F and a BT10-F (50 kW and 10 kW). The normal operating power into the array (Day and Night patterns) was 50 kW.

In 1971, two new 550' towers were erected and the phasing equipment location was changed to the largest of the four field buildings. Construction planning was such that the technical staff was able to switch between the "old" array and the "new" array with minimal loss of air time, to facilitate adjustment of the tuning and phasing equipment for the new array (two towers were common to both arrays).

In 1981, the present facility was opened, utilizing the existing field equipment, but providing a completely new Main Building, with new 50 kW transmitters and control equipment. Again, planning was such that the cutover was made to the new building on April 6, 1981, with less than 10 seconds of lost air time.

The transmitters were built by Continental Electronics of Dallas, Texas, and are designated Model 317C-2. They are capable of a maximum output power of 61 kW at 100% modulation. The final amplifier stage uses two high power tetrode tubes connected in a high-efficiency screen-modulated amplifier, known in the industry as the Weldon Linear. The transmitters are equipped with an automatic power cutback to 12.5 kW in the event of an antenna system fault.

The program material for CFRB is relayed to the transmitter site by two methods. The first is a stereo, 950 MHz link. The second is a pair of matched stereo lines from 2 St. Clair Avenue West to the transmitter site. CFRB transmits in C-QUAM AM stereo, which is the only type of AM-stereo system allowed in Canada. This system operates in a classic manner, with the L+R information amplitude modulating the carrier to the maximum of 1.0 radians, for 100% L-R. In the receiver, this information is recovered by conventional amplitude and phase detection methods, and added algebraically to produce the resultant L and R information. The math is: (L+R) + (L-R) = 2L; (L+R) - (L-R) = 2R. There are decoder chips available for this system.

Control of the CFRB Transmitter Plant is done from the remote point of the studios, through a custom system, utilizing FSK methods, and manufactured by Uni-Tel. At the transmitter site, commands are interpreted by, and some indications are given back with, a CFRB-designed Plant Control System, based around a Struthers-Dunn Process Controller. This microprocessor-based dedicated device does the necessary operations and status checks to permit (for example), a five step pattern change to be accomplished in about 310 milliseconds, with greater safeguards for the equipment than would be possible in a relay-based system of comparable size and cost. The controller also continously investigates the status of certain equipment and sounds alarms if out-of-limits conditions exist.

CFRX (6.070 MHz), began broadcasting in 1937. CFRX has always been co-sited with CFRB, but has used a separate antenna system.

The original antenna system consisted of two 50' vertical towers, configured for a directional radiation pattern to the north-west. The present CFRX array consists of one 50' vertical and provides an omni-directional pattern.

The original CFRX transmitter was designed and built by CFRB technical personnel at the first CFRB transmitter site in Aurora, Ontario. The power output of CFRX has always been 1,000 watts, although in the latter years of the old transmitter, this was difficult to maintain. Problems continued to appear in the operation and maintenance of the original homebuilt transmitter, with a resulting deterioration in audio quality.

Early in 1983 the decision was made to purchase and install a new 1 kW transmitter for CFRX. The present transmitter was delivered in December of 1983 and was commissioned December 31. The new facility is located in a room next to the CFRB transmitters. The transmitter was manufactured by Elcom-Bauer of Sacramento, California. The design is basically their Model 701B, with the tank circuit of the final stage redesigned and an RF driver stage added after the standard RF oscillator card. The transmitter is now designated a 701B-HF. It is a classic plate-modulated design and is capable of producing high levels of modulation continuously, as is required for a 24-hour-a-day operation of CFRX.

The program material is derived from the same links as used for CFRB and is processed at the CFRX audio rack, using CRL processors. The programming is a simulcast of CFRB's, except for a CFRX ID that runs twice an hour.