Technology at Mercia 

23 May 2024

Mercia Sound opened in Coventry on 23 May. MEL LAMBERT visited chief engineer Ian Pettman to look over the station’s technical facilities.



Cover of Radio Month

From ‘Radio Month’ for August 1980

Mercia Sound, broadcasting on 220m medium-wave and 95.9MHz stereo FM, is located in what was formerly a working men’s club in Hertford Place, just off one of the numerous ring roads skirting Coventry’s city centre. The station comprises four studios on the ground floor, and general offices plus a newsroom above.

Technical installation was undertaken on a turnkey basis by Alice (Stancoil), with Sandy Brown Associates acting as overall architectural and acoustic consultants. SBA also supervised the major electrical and mechanical aspects of the station’s construction, whilst Elliott Brothers were responsible for the majority of equipment, inter-studio and jackfield wiring.

Mercia Sound’s chief engineer, Ian Pettman, worked closely with Alice in the design of one or two special facilities, including a high-level source selection switcher, various items of racksroom equipment, and a home-brewed mixer and switching facility for the newsroom. Construction work at the station began in midNovember, following the signing of contracts, and was completed well in time for the IB A Code of Practice tests conducted two to three weeks before the on-air date. Reported cost of the turnkey equipment package, for which Mike Bennett of Alice acted as project manager, was in the neighbourhood of £90,000 [£370,000 in today’s money, allowing for inflation – Ed].

While Ian Pettman may be new to ILR, he feels that his previous experience with BBC local radio has stood him in very good stead. He worked at BBC Radio Manchester for four years, during which time he supervised the installation of new studios and a move from the station’s former premises in Piccadilly Gardens to Oxford Road.

After a spell at the BBC’s training suite in the Langham Centre near BH, Ian was then attached to Radio Leeds, where he directed acceptance tests for the station. Having carried out similar acceptance tests for Radio Brighton, Ian returned to the Langham headquarters and, for a year prior to his joining Mercia Sound, was involved with assessing the technical requirements of equipment specified for BBC local radio.

During his time with the Beeb Ian managed to visit about half the BBC local stations, and over the last year or so has been to see a great number of ILR installations. Although he conceded that the facilities and equipment of ILR and BBC local radio were very similar, the tighter programming structure favoured by commercial radio puts a greater strain on technical resources — particularly the wide-scale use of NAB cartridge machines, which act as a major source of recorded material throughout ILR. I was interested to note that, on the subject of cart machines, Ian found that there appears to be no COP specification for crosstalk between cue and program tracks. Since Mercia plans to use FSK data recorded on the cue track to provide automatic notification of an ad being played out, he has obviously been looking at ways of keeping crosstalk down to inaudible levels.

Ian Pettman

Ian Pettman

Mercia’s technical staff includes a chief engineer, two maintenance engineers and, at present, a trainee assistant. The station will be manned six days a week, the two maintenance staff working a rota of 10½-hour days based on two overlapping shift periods (Monday through Thursday, or Wednesday through Saturday). All programmes will be run on a self-op basis, so there is no need for a technical operator to be in permanent attendance during the station’s broadcasting hours of 5.00 am ’til midnight (7.00 to midnight on Sundays).

Access to the ground floor studios can be gained by passing through a large reception lobby. As a conversation piece in the lobby, a pair of rack-mounted Leevers-Rich Proline 1000 logging machines continuously monitors the station’s off-air output (albeit delayed by a second or two). Equally unusual, a glass window enables visitors to see what’s going on in the main on-air studio. Having entered the correct combination on a special security lock, the visitor passes through into an inner soundproofed area off which lead the two on-air studios, production and talks studios, plus maintenance workshop and racksroom.

The slightly larger of the two main studios is designated as the main on-air studio, while the other functions as a standby and is also used for recordings. Both on-air studios have parallel microphone and monitoring lines running through to a central and very spacious talks studio. A fourth area, which may eventually become a control room for the talks studio, functions at present as a self-contained commercial production facility.

Each on-air studio is equipped with an identical Alice ABCM 16-channel console, a pair of triple-stack ITC cartridge machines, Studer B67 tape machine and two Technics SP10 mkII turntables complete with Stanton arms and D6800EL cartridges.

The input configuration of each console comprises (working from left to right): two stereo gram channels fitted with switchable fader or pushbutton remote starts; four stereo line-level inputs with thumbwheel routing to a total of 14 high-level sources (one of Ian Bettman’s special circuits, and linked to a CMOS-controlled routing unit situated in the racksroom); a central script area; six mono microphone channels for the DJ/announcer and his guest, and/or four mic inputs from the talks studio; a pair of stereo channels for the triple-stacks; a pair of stereo channels for the tape machines, complete with switchable fader or pushbutton remote start and left/right and mono select switches; and, lastly, a pair of modules housing a 7-destination talkback unit, and various monitoring controls. All channels are fitted with prefade listen facilities, but no equalisation or balance controls.

All four high-level input channels feature a series of illuminated switches that light up to show if a particular source is being used elsewhere (“engaged”), and whether a return control line is available. For 4-wire working, a second set of pushbuttons allow various outputs and/or talkback to be routed back to an outside location.

Two of the line-level channels, in conjunction with a PO Telespot system, can also be designated as telephone inputs simply by dialling up the correct thumbwheel assignment. Each of these input modules features a row of pushbuttons for routing the call to air, or for providing talkback to the caller’s handset. The output from each telephone channel is panned a quarter left or right during conference discussions involving more than one caller. A second set of indicators and pushbuttons display the status of a tape-based profanity delay system, and select the particular operating mode (in/out, “real time” and “profanity insert”).


A man at a radio desk

Tony Gilham at the desk in the main on-air studio


A bank of four pushbuttons on each cartridge input channel provide remote start to each slot. In addition, a further row of “follow” buttons enables up to six cartridges to be played in a pre determined sequence via the secondary or tertiary cue tones. Remote starts for the Studer B67 tape machines are also provided on the console modules.

Housed within the centre section of each console are a pair of twin-needle stereo PPMs displaying station output and “monitor” — usually desk output or PFL — plus a single-needle PPM for mono station output; two peak-reading indicators to warn of overload on left and right station output; and the various Davis over-air alarms for MW and VHF transmitters.

Below the meters a row of pushbuttons and level controls enable various monitoring conditions to be set up in both the self-op studio and associated talks studio. A pair of “release” and “accept” buttons on each console, which route a particular studio directly to the outgoing lines to the transmitter, allow swift studio changes to be made in the event of an equipment failure. (Or when a swap of studio is required for routine maintenance.)

Although both areas are equipped with identical Alice consoles, the main on-air studio also has a separate newsreader’s position located to the right of the DJ. A special switch panel houses a bank of duplicate remote control pushbuttons for the six cartridge transports, a mic on/off button and a clock. When the DJ presses a master “News” pushbutton at the top of each hour, an incoming feed from IRN is routed automatically to the console output. At the same time remote control of the cart machines passes to the newsreader.

As soon as the 3-minute optout point is reached, by simply turning on the microphone, IRN will be muted automatically and replaced by the newsreader’s voice. No other control is necessary, however, since an automatic gain control rides levels on the microphone output. Firing off a cartridge also mutes the microphone output, which then needs to be turned on again as soon as the cart ends. Overall control is restored once again as soon as the DJ releases the master “news” switch. By all accounts a remarkably easy-to operate and troublefree system, specially developed by Ian Bettman and fabricated for the station by Alice’s technical staff.


Three images of technical equipment

Top: newsroom mixer/switching unit; right: racksroom; left: newsreader’s switch panel in the main on-air studio


The nearby racksroom houses a couple of Post Office telephone equipment and termination bays, plus three 19-inch units for the station’s hardware: Revox B760 digital FM and Armstrong AM tuners for off-air reception, a Gent crystal-controlled master clock; Davis alarm and monitoring equipment; a pair of Alice TBU3 automatic telephone balancing units with ducking; a pretty standard-looking Technics RS1500 deck to provide tape delay during phone-in programmes; an MJS Model 401 noise and level test set for lines tests; and a Sony TC-K55 cassette deck for over-night announcements. The Technic’s dual capstan transport is said to ensure flutter-free record/replay via a simple tape loop system.

A small newsroom on the first floor is equipped with a simple, but extremely comprehensive, mixer and switching unit designed by Ian Pettman and custom-built by Alice. A variety of high-level sources ranging from the local council chambers to an IRN feed, plus the output from a telephone key and lamp unit, can be routed through the mixer, adjusted in level, monitored on headphones, and then recorded on a Revox B77 reel-to-reel or ITC Series 99 cart machine.

Alternatively, by simply depressing a single pushbutton, remote starts for the Revox and cart machine, as well as talkback, are automatically routed to a supplementary six-input mixer in a nearby voice booth. Here a journalist can conduct interviews over the telephone or with a live guest, record voice reports with or without actuality inserts played in from a Uher or cassette machine, or take in a report from an outside source. The entire set up is very flexible and has been purpose-built for people with the minimum of technical expertise.

When the time came for IBA Code of Practice tests, Mercia Sound found itself being subjected to one of the most demanding worse-path measurements ever conducted at an ILR station. As many readers may be aware, Mike Bennett, project manager for the Mercia turnkey installation, prior to joining Alice was previously employed by the Authority’s Quality Control Section. One can only assume that in not wishing to favour the handiwork of an ex-colleague, IBA engineers were particularly scrupulous in their technical assessment of the station. (It’s also worth remembering that Mercia places particular emphasis on its operational flexibility, which means that the path from live or recorded source to transmitter could vary enormously throughout the day.)


Alice ad


In the event, the following — but perfectly reasonable — worse path was chosen for the COP tests: from racksroom to production studio via tie line; back to racksroom via another tie line; to main on-air studio via the outside source selector network; back to racksroom via the programme chain; to standby studio via a second trip through the outside source selector network and a DA; to the on-air switcher and monitoring unit via another DA; and, finally, to the IBA’s output terminations. Quality control engineers also looped out and tested all the grams and tape machines in use throughout the station.

When Ian Pettman put a test meter across the same path prior to final COP measurements, he found the overall insertion gain to be only O.1dB, and frequency response 0.5dB down at 15kHz. Not surprisingly he is particularly happy with the present installation, and considers Mike Bennett to be an “extremely gifted engineer; one of the best systems engineers I have met.” However, Ian also points out that he received a great deal of assistance from all the station’s staff, as well as the other ILR and BBC chief engineers to whom he has spoken in the past.


From the Nick Taylor collection in the Transdiffusion archives


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