Police on Medium Wave

In these days of sophisticated digital encrypted radio networks which enable our emergency service personnel to remain in constant secure communication with their control rooms whether in their vehicles or on foot, it is easy to forget just how recently such marvels were confined to the realms of fiction. In the 1950s an adequate supply of pennies was almost as essential to the fireman as his axe – the only way he could contact his control room from the scene of a fire was from the nearest telephone box. The same was true of the policeman on foot patrol until the late 1960s, unless he worked in an area with police pillars or Tardis-style police boxes.

When was radio first used by the emergency services? Incredible as it seems, it was actually in 1900, the last full year of Queen Victoria’s reign, during the building of Streatham Fire Station in London. It seems that the fire authorities wanted to pass fire calls from a street station at Streatham Green to a temporary fire station in Mitcham Lane. They were refused permission to run overhead telephone wires and the GPO demanded the ridiculous sum of £280 to lay underground cables, hardly acceptable for a permanent link let alone a temporary one. The innovative solution was to install a Marconi spark-gap transmitter in a caravan parked alongside the Streatham Ironmongery Stores and receiving equipment at the temporary fire station. Apparently the equipment gave satisfactory results. The frequency used is not recorded; at that period it is doubtful if anyone knew or cared.

For the first base to mobile system we have to jump forward to 1922 when the Metropolitan Police in London began installing receivers in a few of their vehicles to receive telegraphy (Morse) transmissions from a central control room. The system initially used a frequency around 400 kHz, but this was soon changed to 2000 kHz. For the first time a police force was able to communicate with its mobile units and dispatch them to incidents from wherever they happened to be.

Despite the obvious limitations of the Met’s one-way telegraphy system, no doubt it proved highly effective in the fight against crime. Rather surprisingly the idea was not adopted by other forces, and it was not until the General Strike of 1926 that other police forces began looking to radio. The perceived problem at that time was not so much communication with mobiles, but rather communication between police forces in the event of civil insurrection accompanied by an interruption to telephone services. Their paranoia is perhaps understandable given that the Russian Revolution was only nine years earlier, and it did have a useful side effect – it brought the potential of radio communication to the notice of several Chief Constables.

The BBC already had a number of broadcasting stations serving the main population centres and the police saw these as a useful communications medium. Typical of such arrangements was that adopted in North-East England; each Chief Constable in the region simply installed a standard broadcast receiver in his office and monitored 5NO, the BBC’s Newcastle station, which broadcast from Blandford House (now the home of the Discovery Museum). Suitable receivers were by no means cheap; the Chief Constable of Durham, for example, had to find £30 for his 4-valve receiver – and he got rather a bargain, as the set was valued at £80. Any force requiring assistance would send a message by any means at his disposal to the Newcastle studios at 54 New Bridge Street, and this would then be read over the air and heard by other forces in the area. Coincidentally 5NO changed frequency slightly (from 742 to 737 kHz) for a few weeks beginning in March 1926!

Other more direct arrangements were made using equipment borrowed from radio amateurs. Equipment belonging to a Mr O.B. Kellett (GSKL), for instance, was used to link the headquarters of Southport Police with that of the Lancashire Constabulary at Preston.

After the strike many radio amateurs remained closely associated with their local police and most of the subsequent pioneering work in the field of base-mobile communications can be attributed directly to them.

The early thirties saw the opening of a number of such schemes, all using telegraphy on MF frequencies just above the medium wave broadcasting band, in what was then called the Trawler Band. In 1931, Nottingham City Police set up a two-way system under the auspices of Mr. H. B. Old (G2VQ), which linked the City’s patrol cars with their headquarters using locally manufactured equipment. In the following year there were similar schemes introduced in Liverpool – a two-way system devised by Mr I. Auchterlonie (G6OM) and Mr O. B. Kellett (G5KL) – and in Stockport. Birmingham City Police too introduced a MF base-mobile system at around the same time, thanks to Mr George Brown (G5BJ).

Two schemes, however, deserve special mention as they pointed the way to what was to be a national scheme. At first sight the scheme introduced by Newcastle-upon-Tyne City Police in 1933 does not seem very different from the others, indeed in one respect it was less ambitious. Like the others it employed telegraphy on an MF frequency, in fact they used modified aircraft equipment manufactured by Standard Telephone and Cables, but unlike most of the others it was only a one-way system. The transmitter was located in their newly opened Pilgrim Street Headquarters and receivers were installed in both of the City’s patrol cars.

It was what happened in 1934, however, that marked out Newcastle’s scheme as different from the others, because in that year receivers tuned to Newcastle’s frequency were also installed in Gateshead Borough’s only police car and in three belonging to Durham County Constabulary. Private-wire telephone links already existed between the headquarters of the three forces, so messages for the Durham or Gateshead vehicles would be passed verbally from the respective headquarters to the Newcastle operator who then tapped them out on his Morse key.

In 1935 this idea was taken up by Manchester City Police on a rather grander scale. They introduced an MF system which covered no less than six police force areas – Manchester, Bolton, Oldham, Rochdale, Salford and Cheshire (Altrincham Division). The radio station was located at Heaton Park, Manchester, and all of the fixed and mobile equipment was manufactured at Heaton Park by a team of technicians led by Mr I. Auchterlonie and Mr O.B. Kellett, who were by then serving policemen. Manchester’s scheme was predominantly one-way, but a single two-way link was employed for communication with Manchester’s CID night-squad van.

Following the undoubted success of the shared MF telegraphy schemes in Newcastle-upon-Tyne and Manchester, the Home Office formulated the Medium Frequency Regional Scheme, which entailed a network of Regional Wireless Stations covering the entire country. The Chief Constable of Nottingham City Police, at the instigation of radio amateur Mr H.B. Old, had shown particular interest in the idea, so, in 1938, the Home Office approved the setting up of the first Regional Wireless Station at Stanton, Nottingham which was to serve the counties of Nottinghamshire, Derbyshire, Leicestershire, Lincolnshire, Northamptonshire and Rutland, as well as a number of city forces in the area, using a single frequency in the 1600-1800 kHz band. Stanton opened on July 1st. 1939 with Mr H.B. Old as Regional Engineer and Mr O.B. Kellett as Experimental Wireless Technician.

As with the Newcastle and Manchester systems, messages for transmission to vehicles were passed to the control room by private-wire telephone links, but unlike those systems, the new station operated on telephony (voice) rather than telegraphy. It would no longer be necessary for large numbers of police officers to be trained in Morse code.

Although the Stanton station was essentially experimental in nature, it quickly proved its worth, and after only a few weeks of operation, the Home Office approved the building of a further eight similar stations to complete coverage of England. Even the outbreak of war did not interfere with this programme, and site-selection and building work went ahead without delay. Overseeing the work was the newly formed Communications Branch of the Home Office.

Up to this time the Post Office had issued callsigns for individual police schemes as required, so there was GWW for the Met, GTM in Liverpool, GWB in Manchester and MVQ in Nottingham etc. With the formation of the Home Office Communications Branch, it was decided that they would take over responsibility for all police callsign allocations using the series M2AA-M2ZZ.

By the end of 1942 all nine Regional Wireless Stations were in operation. The Marley Hill station was typical. It was erected alongside a distribution reservoir on an elevated site in the north of County Durham about three and a half miles south-west of Newcastle-upon-Tyne. The site was dominated by a 140 foot mast radiator and nearby was a flat-roofed building housing the transmitters, control room and offices.

mf_regionalThe main transmitter (Marconi Ship-to-Shore type) was of 1 Kilowatt and there was a 300 watt standby unit to ensure continuity of service; both could quite adequately cover the whole of the station’s service area – Northumberland, County Durham and the North Riding of Yorkshire. Although Marley Hill, like the other stations in the MF Scheme, provided only a one-way service it did have receiving facilities. These enabled Marley Hill to continuously monitor the transmissions of the neighbouring Regional Wireless Stations at Kippax and Billinge. As these stations also monitored Marley Hill and each other, two-way communication between the wireless stations was possible. The receiver was made by Eddystone (700 series) and the receiving antenna was a simple dipole supported on wooden poles.

Marley Hill began service in 1942 with a staff of around seventeen under Regional Wireless Engineer, Mr A.T. Martin. (From 1945 to 1972 the Regional Wireless Engineer at Marley Hill was a gentleman who has featured in virtually every phase of the story so far, Mr Oswald B. Kellett. Both Mr Kellett and Mr H.B. Old were later awarded the MBE for their services to communications).

Durham County Constabulary was the largest of the twelve police forces in Marley Hill’s service area and it immediately adopted the MF Regional Scheme as a direct replacement for the one-way telegraphy service provided by Newcastle City Police. The County’s six patrol cars were sent to the GEC factory in Bradford, Yorkshire to be fitted with suitable mobile receivers, and fixed receivers were installed at the force’s Durham City headquarters and in each of the divisional police stations. Arrangements were also made with the GPO to extend Durham’s already extensive private-wire telephone network to the wireless station by means of an additional link from the switchboard at Consett Divisional Station to Marley Hill.

The system worked well – messages for the cars were passed verbally to Marley Hill and within seconds were repeated over the air by the civilian operators – “RL to Andrew 3, proceed to… “.

The fact that the scheme employed telephony rather than telegraphy meant it could be used by any officer and not just those trained in Morse, but there were problems caused by interference from North Sea fishing fleets which used the same wave band. This had also affected the telegraphy service but was more noticeable with the new telephony system. The biggest drawback, of course, was that the system was strictly one-way; the officers manning the mobile units had no means of replying other than by using the public telephone system.

Two-way telegraphy systems had been working successfully in some city areas for many years and there would be obvious advantages if this could be provided with the telephony system too. Experiments with two-way telephony communications on MF were carried out at the Cheveley Regional Wireless Station in 1942 but the results were far from satisfactory and it became clear that MF was completely unsuitable for the purpose.

When this became available, the Home Office approved its use in urban areas with populations exceeding 75,000 and offered generous grants as an incentive. Many city forces took up the offer and from 1942 the two types of system operated side by side, two-way systems in some cities and the MF Regional Scheme elsewhere. The spread of VHF schemes was only limited by the availability of the equipment, much of which was being diverted for use by the ARP (Civil Defence) services.In fact, even before the first of the Regional Wireless Stations opened in 1939, it had become clear that future of police communications lay not with MF, but rather with VHF systems. Experiments at Manchester’s Heaton Park station in 1937 had demonstrated that, despite popular belief, VHF could indeed be used for base-mobile communication, even in cities. After further work by the Metropolitan and Birmingham City forces, the Home Office Communications Branch conducted tests in several areas of the country, and in 1940 they asked GEC to design and produce suitable fixed and mobile VHF telephony equipment.

After the war the move from MF to VHF resumed and not just in the cities, the plan called for multi-station schemes covering county areas too. Four Home Office test teams, recruited mostly from the National Fire Service, toured the country carrying out coverage tests, and one by one the VHF schemes were installed.

The first two, in 1946, were for Bedfordshire and Hertfordshire, previously served by the Cheveley Regional Wireless Station. Police forces were still joining the MF schemes – Northumberland Constabulary and South Shields Borough Police began using the Marley Hill Regional Wireless Station as late as 1946 and 1947 respectively – but it was a temporary measure and by 1950 virtually the whole country was served by police VHF schemes operating in the 95-100 MHz band.

The Regional Wireless Stations were redundant – but the sites were retained and redesignated Regional Wireless Depots. Their new function was to maintain the fixed and mobile equipment used by the various police, and later fire-service, schemes within their areas.

Most MF masts were removed and replaced by slightly smaller towers carrying VHF arrays, but these were not used as part of any police schemes. Their role was simply to provide two-way communication with service vans based at the depots. A few depots retained their existing masts for a while and mounted their VHF aerials on those, but the last of the old MF masts, that at Cranbrook, was gone by 1972.

All nine depots remained in service until the 1990s, indeed a tenth at Harrow had opened in 1972, but, in keeping with government policy, they were then privatised and many have since closed and disappeared from the landscape. A sad end for these pioneering establishments after many decades of public service.


  1. Police Interception Unit

    To operate their new radio system Newcastle City Police had to train a number of officers in Morse code This had a rather unexpected consequence in 1938 when those officers were asked to set up an interception unit in Newcastle for the Radio Security Service. They, along with some 1200 other volunteers throughout the country, gave valuable service throughout World War II intercepting messages from both friendly and enemy sources and providing a large part of the raw material for the famous Bletchley Park decrypts.

    The Police Radio Interception Unit operated from the City’s West End Police Station on Arthurs Hill using two Hallicrafters receivers, a Super Skyrider and a Skyrider 23. The vast majority of the intercepted messages were, of course, in code and were simply forwarded to the RSS headquarters in London to be decoded. Rarely did the volunteer interceptors have any idea as to the nature or significance of the messages, but on one occasion they got just a clue. At 1905 on June 15th 1941 PC Ed Barron picked up the following message on 7050 KHz:


    then followed 25 five-figure code groups, and finally

    “AR (end of message) PRAGUE”. (Tyne & Wear Archives Service Ref. T136-87)

    Most unusually, the RSS sent a personal message of thanks to the officer concerned which ended “Apparently this message is of great importance”.

  2. Callsigns

    The callsigns allocated to the later police VHF schemes were almost always derived from that of the MF Wireless Station which had previously served the area – they just omitted the “R” from the callsign and added a letter to the end. So, for schemes in the area served by Marley Hill (callsign M2RL) they used the range M2LA- M2LZ. Thus there was, for example, M2LA for Durham Constabularly, M2LB for Northumberland Constabulary, M2LG for Gateshead, M2LL for South Shields, M2LK for Newcastle-upon-Tyne, M2LN for Sunderland and M2LQ for Tynemouth. Similarly there were the M2V’s, M2K’s, M2H’s, M2X’s, M2Y’s, M2Q’s and M2N’s derived from the callsigns of Cheveley, Cranbrook, Hannington, Kippax, Romsley, Shapwick and Stanton respectively. Billinge (M2RB) was slightly different, it gave birth to both M2B’s and M2C’s because there were far too many police forces in its area for the M2BA-M2BZ series. So we had M2BL for Barrow-in-Furress Borough Police, M2BU for. Carlisle, M2CL for Oldham and M2CK for Manchester, and then there was perhaps the best known police callsign in the world, that of Lancashire Constabulary, M2BD, remember Z-Cars, “BD to Z-Victor 1 “. Later fire-service schemes generally followed the same pattern. Of course there were many exceptions including the “Met”, which used M2MP among others, and some fire services which opted for callsigns in the range M2FA-M2FZ. Schemes in Scotland used M2A’s, M2U’s and M2Z’s, while those in the Isle of Mann and Wales used the M2M’s and M2W’s respectively.

    In the days of the early telephony MF and VHF radio schemes the phonetic alphabet in civilian use was that of the GPO. Its use within the police schemes varied enormously. Some Schemes used it for mobile callsigns only “RL to Benjamin 5” (Northumberland on MF 1946-1951), others used it for both base and mobiles “Lucy Lucy to Lucy 2” (South Shields’ scheme from 1951), while a few did not use it at all “LK to K6” (Newcastle’s scheme from 1942). From 1956 the NATO phonetic alphabet was used – Alpha, Bravo……Yankee, Zulu replaced Andrew, Benjamin……Yellow, Zebra.

Copyright Brian Pears, © 1996, 2009

An older version of this paper was published in 1996 in “Medium Wave News”, the newsletter of the Medium Wave Circle (Jul/Aug 1996, Vol 42 No 3), and in 2005 on the DTELS.ORG (Home Office Directorate of Telecommunications) website – http://www.dtels.org/html/police_on_mf.html