What happens at Crawley Court? 

6 June 2024 tbs.pm/81685

 

Cover of Radio Month

From Radio Month for March 1980

The Independent Broadcasting Authority, through its Engineering Division, is responsible for the selection of suitable television and radio transmitter sites; the building, operation and maintenance of transmitters; and research and development into the future technical needs of the ITV and ILR services. The majority of the Authority’s administrative staff are based at its Knightsbridge headquarters in Brompton Road, but the Engineering Division, together with a substantial part of the Finance and Staff Administration and Services Division, are now headquartered at Crawley Court in Hampshire.

A total of around 300 engineers and technicians work within the IBA’s Engineering Division, either based at Crawley Court or at one of the Authority’s four regional engineering centres. In fact, about two-thirds of all IBA staff are employed by the Engineering Division in some capacity or another.

To describe fully the myriad activities with which the Engineering Division is concerned would require a lot more space than I have available in this article. Instead, to give at least a flavour of the Authority’s close involvement with independent local radio companies in particular, it may be worth focusing attention on just one department. The network operations and maintenance department under Alan James has responsibility for two main areas: technical quality control within each ITV and ILR station, plus liaison with the Post Office over the provision of dedicated music lines between each station and transmitter sites. (Certain ILR stations, including Piccadilly Radio and Radio Tees, are provided with UHF microwave links to their FM transmitter sites instead of music lines.)

Head of the quality control section is Phil Darby, who oversees a total staff of seven engineers, including principal engineer Chris Daubney and senior engineers Chris Hibbert and Peter Marshall. Because of their particular engineering background, Chris Hibbert specialises in the requirements of the ILR service (he is also secretary of the Code of Practice Working Party), while Peter Marshall concerns himself with television. However, all engineers within the quality control section may be required to make regular visits to both radio and television installations, and so need to be fully conversant with the day-to-day operation of both services.

Despite the fact that the quality control section is particularly busy at the moment — what with the forthcoming introduction of a second independent television channel, the possibility of new ITV programme contractors being appointed, and imminent on-air dates for the next round of ILR stations — Chris Daubney and Chris Hibbert managed to find time during my recent visit to Crawley Court to outline the section’s particular area of responsibility.

They began by explaining that the quality control section maintains a close watch on the technical standards of each new ILR installtion, along with its subsequent day-to-day operation. In particular, the section is responsible for making routine checks that Code of Practice requirements for studio and control room equipment and acoustics are being met.

Prior to the introduction of the ILR service, it was the policy of the IBA to continuously monitor the programme output of all television companies. For radio, however, such a policy would have meant tying up a prohibitive number of staff. It was decided therefore that to try and compensate for the lack of continuous monitoring of ILR output, the quality control section would pay regular yearly visits to each independent local radio station. A longer inspection is also made to new stations before their on-air date, so that a more extensive series of tests can be carried out than would be possible during the section’s annual visits.

 

Crawley Court

The IBA’s eight-year old engineering headquarters at Crawley Court near Winchester, home base for the 300 or so engineers who look after the technical requirements of the ITV and ILR services

 

Members of the quality control section are quick to point out that the IBA’s Code of Practice requirements for equipment are not meant to be regarded as an equipment specification. It is more appropriate, they consider, to view the code as a ‘performance requirement’ for day-to-day operation of a studio installation. And Code of Practice covers not just the equipment used by a station, but also its maintenance philosophy. (After all, to obtain the very best results from any item of broadcasting hardware, it needs to be properly looked after.)

During examinations of a station’s technical facilities, visiting IBA engineers look for the ‘worst-case’ path through equipment; in other words the longest signal path that an item of programme material might take from being recorded to eventual transmission. Usually this worst-case path involves a particular item being recorded through a production mixer onto a tape machine, and the tape being transferred to another machine for editing (probably through another mixer). The completed tape might then be taken into a presentation suite for replay on a third tape machine, through an on-air mixer and hence via outgoing music lines to the transmitter.

“What we would do in that case,” Chris Hibbert explained, “would be to loop out the tape recorders, join the three mixers together, inject tone at the front end of the first one and then measure what comes out at the end. Having checked out the ‘static’ equipment, we would measure each tape machine and cart machine separately, by making a recording on one machine and replaying it on another. Tape frequently gets moved around a station, so we need to check record and replay head height adjustment and azimuth. For a cartridge machine we would probably go to the production studio to record a cart, and then replay it from the on-air studio.”

Apart from looking at frequency response, signal-to-noise ratio, distortion, stereo phase and crosstalk on tape machines and mixers, another parameter specified by Code of Practice is the headroom or overload capability of a microphone channel’s front-end. This is particularly important, Chris Hibbert stressed, in mixers designed for self-operation. Output levels can vary a great deal when a desk is being used by an inexperienced DJ or announcer, resulting in severe distortion if sufficient headroom hasn’t been provided. Code of Practice calls for 20dB of overload margin, a value which is checked by setting up a particular channel for its ‘nominal’ gain setting — 50dB for example — and then injecting a signal 20dB higher than this. After pulling down the channel fader to restore the previous OdB output level, there should be no increase in distortion above that specified for conventional gain settings.

But gaining access to the on-air programme chain during the quality control section’s annual visits is not always possible, simply because some of the equipment may be in constant use around the clock. Chris Hibbert went on to outline the section’s approach in such circumstances.

“What we have to do because of 24-hour operation is to check out the worst-path on a new station before it goes on air. This means that our initial visit needs to be deeper and more searching than the yearly routine visits. Then instead of checking out worst-path, which could possibly mean shutting down the station, we look at ‘studio-path’. This involves checking out a single mixer, possibly after moving a presenter out to a spare studio that can be routed directly to air.

“But if a programme company totally re-equips a studio, then the IBA would want to do a worst-path again. And this would involve not just testing out the mixers and so on. Equipment bought from a manufacturer may be all very fine by itself, but when it is interfaced with the rest of the station — and the signal passes through racks, tie lines and so on — you can get phase reversal and unbalanced loads being put across it. All of which needs to be checked out as well. If you’ve got a long signal path going through multiple jackfields, its easy to end up with any even number of phase reversals, and the end result can sound satisfactory. But if a fault develops and you have to overplug something, the end result will be absolute phase cancellation and a station’s mono audience ends up with nothing.”

On the subject of equipment meeting Code of Practice, most manufacturers now know what is required in the way of test performance. As a result the majority of them aim for something better than Code requirements. Chris Hibbert feels however that manufacturers aiming slavishly at Code tolerances can present serious drawbacks.

“If a manufacturer designs something hard up to Code’s limits and leaves very little room at all, it’s rather unfair to the station, because within a very short space of time they’re going to be struggling. Although we cannot stop a radio company from buying a piece of equipment which is just going to meet Code — that’s their choice, after all — we would advise them on a friendly basis that this may not be the best thing for them to do. We like to think that we’re fairly successful in developing a good working relationship between ourselves and the radio companies on the engineering level.”

A certain amount of that empathy stems from the Code of Practice Working Party, which drew up the present Code by agreement between the IBA and representatives from the present programme companies chief engineers. If a programme company wants to amend the Code for any reason, it can ask to reconvene the working party.

“We don’t deliberately want to change Code of Practice,” Chris Hibbert emphasised, “simply for the sake of it. At the moment everybody seems to be fairly happy that the Code is as good as it need to be. It’s taken several attempts, and the present Code doesn’t have a lot of similarities with the first one. It’s I evolved with experience, because when the IBA started there wasn’t a wealth of experience within the Authority about the requirements of sound studios. As a result it was based on advice from contacts throughout the industry, plus a bit of intuition, if you like.

“For instance, the very first Code of Practice that the IBA produced didn’t distinguish between cartridge and reel-to-reel machines: there was one Code for magnetic recorders, and that was it.

“It didn’t take us very long to realise that state-of-the-art in cartridge recorders didn’t lend itself to meeting a reel-to-reel spec. Consequently, based on experience and liaison with the programme companies, we’ve worked out what was considered to be a realistic performance for a well-maintained cartridge machine, which is now a separate part of the Code.”

 

A man sits at an audio desk

Chris Daubney of the IBA Engineering Division’s quality control section with the IBA’s experimental surround-sound desk, currently installed in a mobile unit

 

I asked Chris Hibbert about the use of cassette machines in certain stations. Code of Practice for reel-to-reel machines distinguishes between studio and ‘newsroom’ models for use in mobile recording, but doesn’t mention cassettes.

“As far as I know,” he replied, “we don’t acknowledge their existence. There is a spec for portable newsroom tape machines, so if a station chooses to use cassette recorders we expect them to meet Code of Practice. If we had good reason to believe that such a machine was being used for programme material, to produce news cuts that were going to be transmitted, then we would consider it quite valid for us to want to test it.”

Were any important lessons learned during the installation of the first round of 19 ILR stations, I asked. Technical and operational problems that were common to more than one new station, perhaps? Chris Daubney’s reply was perhaps predictable.

“All 19 were different; we learned something new from all of them! We faced different problems at every station. Often it depends on how early we became involved with the problems. And with the early stations too the architectural, acoustical and electronics consultants were themselves learning about how Code of Practice was to be implemented. It became easier as we worked our way down the 19 stations because we tended to find in some areas the same consultants coming back again to different installations.

“But there were 19 different buildings, 19 different companies and 19 different operational philosophies; all of which were valid. It was interesting to see such different ideas about how each station should be run, since there is no way of saying that what worked at Sheffield with Radio Hallam, was going to work at, say, Plymouth Sound. And we shall have nine sets of problems with Phase II, and 15 more sets with the forthcoming Phase III.

“The most important thing that’s happened in the intervening four years since the last ILR company went on-air is that the stations have now settled down, including some of the smaller ones. After all, we are going to smaller-generation stations in Phases II and III. I know we’ve got the Bristol and Leeds consortia to come, but there will also be the Gloucester/Cheltenhams, and even the Bury St Edmunds of this world in the next 15 stations. They are all much smaller stations, working on much tighter budgets than, say, Capital or Clyde. For such stations, it will be important to see how various things have stood up to the wear and tear of 24-hour operation with relatively low staffing levels.

“For example, has it paid off to go for expensive capital equipment, and hope you can keep the revenue cost down because, hopefully, the maintenance costs will be lower? Or should you go for cheaper equipment and then phase it out earlier? Those two philosophies tended to characterise early stations in a fairly random way, and I hope lessons have been learned — not about which equipment meets Code of Practice, but what it is economically sensible to buy.”

On the subject of increasing costs of running a station, what about automation in ILR? Can we expect a change of policy in the near future?

“It’s possibly outside our brief, but at the end of the day the technicalities have to be investigated fairly thoroughly to see if we would be satisfied. I don’t actually believe that when it comes down to it the engineering decision has a vast amount to do with whether a station wants to go for automated broadcasting. There are all sorts of other things to be sorted out, more to do with automated presentation. While it isn’t technically feasible with present cartridge machines, maybe in a year or two some form of automation may be possible.”

To improve intelligibility for medium-wave listeners, Code of Practice allows 10dB of compression to be applied to a station’s AM output, followed by hard limiting. FM output, on the other hand, must be totally unaffected, apart from providing overall peak limiting to protect the transmitter. Were there any changes likely in the near future, I asked, given the increasing number of selective-band compressor-limiters that were appearing on the market?

Chris Daubney told me that while it is perfectly inorder to compress material being recorded on cart — commercials, station idents etc — or during the preparation of pre-recorded material, stations are not allowed to provide overall compression of VHF output, which must be broadcast in an “absolutely pristine” condition.

“The only thing being contemplated in that field is the problem of pre-emphasis technique,” he continued. “But since there are millions of FM receivers equipped with 50mu S de emphasis circuits in current use, we cannot do too much about it yet. 50mu S is becoming more and more of a problem on FM as microphones, lines and equipment all deveop a higher and higher top end performance. And the style of music programming is changing as well: more and more electronic material with flatter and flatter spectra.

“Pre emphasis is no longer something you can let the system have, simply because the argument that allows you to preemphasise signals and still get away with it is no longer valid. This assumed that the programme spectra effectively fell away at 50mu S — otherwise you wouldn’t need to boost it — which is no longer true. With flatter spectra you’re getting more and more lift at the top end and, as a result, the maximum deviation of FM transmitters is now quite frequently being controlled by the high-frequency rather than low-frequency energy”.

 

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