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PETA - Portable Electronic Traffic Analyser - S350

Page history last edited by Alan Hartley-Smith 5 months, 3 weeks ago




Input from Malcolm Granville, a Marconi apprentice in 1960

Motorists of the world can thank Marconi for having the world's first radar speed trap equipment. I think it was developed at Baddow in the early 60s.  I remember being asked to make some parts for the prototype PETA. (Portable Electronic Traffic Analyser)

I was reminded of this when I came across this website of vintage police radio equipment. http://www.dtels.org/html/speed_traps_vr_10.html

The manual can be found at  http://www.vmarsmanuals.co.uk/archive/4023_Marconi_portable_electronic_traffic_analyser_S350.pdf

(Note from IJG:- Our very own copy can be found here)


I notice in the spares list that Marconi charged customers a shilling each for quarter watt resistors fifty years ago!


Marconi didn't develop the technology any further and the police rapidly equipped with more portable and accurate Swiss equipment.

Input from David Samways

While I was doing a spell at Marconi College they were doing some testing on PETA, maybe a prototype I don’t know, and a few of us apprentices were used as guinea pigs to test the operational aspects of the unit to simulate police training.  It included how to switch it on and off, and set it up, and taking notes for improvements etc.  We weren’t allowed to test it though on vehicles in the College car park!


Having said that, whilst traversing the main road one evening from Chelmsford to the Little Chef near Brentwood (as one did regularly) I was stopped by the police for ‘speeding’ and low and behold there was PETA.  With my newly acquired knowledge I waved my car keys just 18” away from the unit and it went off the Richter scale.  The police then informed me it was under test and I would have only received a warning.  I just replied “thank you officer” and said nothing else.


Input from Ian Gillis

For Systems/Sales PETA was allocated to Alec Stuart's Military and Naval Projects Group, of which I was a sproggy member. IIRC this illogical allocation of a police radar to such a group was because we had handled a similar device that measured the muzzle velocity of shells and hence could predict where the shells would land. The name of the artillery radar is on the tip of my tongue, but...

Later addition - I remember -​ it was EVA - not Braun but an acronym for Electronic Velocity Analyser (you had to spell things out for the pongos!).

Even later addition: BVR ("Beaver" - no laughing please…) added Bearing to Velocity and Range. Here is an article in MCATP for May 1963 - I don't think any were sold.


I remember that the Group was sometimes involved as acting as or finding expert witnesses in litigation. The story that sticks in my mind was about a court case where a milk float had been clocked at an illegal speed, and the defendant produced his own expert witness who said that the electromagnetic tintinnabulation of the aluminium milk bottle caps had produced a false reading!


Input from Nigel Clarke

It would seem that PETA continued to find odd "homes".


In the late 60s PETA service and calibration was carried out in the Marconi Marine test room on Westway by a gentleman named Brian Salmons, not too sure about the surname spelling, who normally dealt with the TV and audio equipment used for shipborne entertainment.


I believe there was a calibrated stretch of road somewhere that was used for final testing but Brian's checks included running the unit alongside the adjacent A12, with not always the best of reactions from the passing motorists who probably came to realise that a white lab coat isn't generally part of an official police uniform:-)


Input from Barry France

I seem to remember that Peter Ball was very involved with PETA. I think the missile tracking radar was called Symbolin (the spelling may be wrong) but was mainly an EMI development.
I must get around to clearing out my loft one day as I am sure I have all sorts of Marconi goodies hidden away somewhere.

Input from Richard Worby

The radar to which you refer was in fact CYMBELINE, and was principally a mortar locating radar. Its primary  purpose was to track incoming mortars and determine whence they came, such that fire could be returned. 


I was marketing director of Thorn EMI radar division for a time in the eighties, and I know this radar very well. We sold many of them at home and abroad.  It was a strange beast, having a Foster scanner and equipped with a Wankel engine for power generation.


For more info, follow this link:   http://en.wikipedia.org/wiki/Cymbeline_(radar)


Input from Bernard de Neumann

Is COBRA (COunter Battery RAdar) a descendant?


Input from Richard Worby

In a word - YES! Whereas Cymbeline was a mortar locator, COBRA could locate multiple launches of various artillery munitions. It was very capable, but equally expensive. Hence the consortium of France, Germany and the UK which developed it. Thorn-EMI radar Division was part of this, but of course didn't remain T-EMI for long. First T-EMI ate MEL, whereupon I became a victim of rationalisation, (aka chucked out), then RACAL ate T-EMI, then Thales ate everybody. It's hard now to find traces of the companies we all grew up with.


Input from Alan Matthews 

I have the Data Sheets - K1 for EVA and K2 for PETA. These are from the "Marconi Radar Systems "  Catalogue of 1970/71 with 7 pages for the EVA and 5 pages for PETA


Input from Bob Mountford

PETA - I remember one on the A12 in Boreham in the lay-by opposite the pub, memory fails me as to the name. And once, on one of my journeys North to visit a  Cement works, I got lost somewhere around Goole. Saw a police car, pulled up to ask for directions, realised I was screening their PETA device as they became agitated  telling me to move on. I took my time and told them that it was made by Marconi and I worked for them. All the while cars were speeding by. Frustrated Fuzz!


Input from Mike Rignall
I can confirm that PETA was developed at Great Baddow in the early 60s under the guidance of Mervyn Morgan who led a Doppler radar group The equipment was given much publicity by the Autocar mag, that published a review of the device in August 1965 where its accuracy was confirmed - see here

The development was quite interesting, since it was one of the first radars to use transistors and, looking at the circuitry, it is fascinating to note that a valve , a 12AT7, was needed to get a high input resistance, no CMOS op amps in those days. Much early development was done in conjunction with the Lancashire Constabulary, but the first public demonstration was given to the Cambridge police. There was quite a tale to tell about this demo, since the prototype was tested at West Hanningfield early in the morning, and, when the PETA was loaded into the Hillman van, the display meter unit was overlooked and it got run over . Fortunately is was quickly repaired and Mervyn made great play of the ruggedness of transistorised equipment to the Cambridge police.

It is interesting that when the police became used to PETA, they trusted it. The radar did have two calibration oscillators built into it and, although not crystal controlled, they held their frequency to better than 1/4 MPH, which was less than the thickness of the pointer on the meter. When I look at the circuitry, I often think that now, in the days of op amps and umpteen bit processors, how the design would look. Most of the work was done with OC71 pnp transistors with an fb of 1Mhz. Now, with a solid state X band osc, how different it would look, no need for the ringing choke HV power supply to keep the klystron working, with all of the attendant system noise it generated.
Those were the days!

Input from Nick Pinnock
“The biter bit”, to use an old-fashioned phrase, or nearly so.
I remember arriving for work at the PCTA at Great Baddow one day in 1970, and a young colleague, an apprentice, recounted how he had been approaching the village rather fast that morning. “Yikes! Crikey! Goodness me! That’s a policeman with a Marconi grey box by the roadside,” he said to himself. (Since this is a family website, various expletives have been altered.)

A screech of brakes preceded his being apprehended by the fuzz, armed with a box he himself had helped to create, he said.
The police don’t get a very good press, do they? All they wanted to do was to calibrate his own speedometer, after all.


Input from Ian Gillis

In the early 1970's the UK Police Forces were seeking a replacement for PETA and a contract was placed by the Home Office for examination of a optical technique for speed measurement. A device with the required accuracy, known as OSCAR, was demonstrated to Police Forces but was not adopted by them, partly because they were reluctant to spend the time and effort involved in convincing magistrates and juries of the validity of a new technique, and partly because a very cheap form of electronic stop watch which could be used (albeit with less accuracy) by police officers in a vehicle became available at the same time.






Comments (2)

Ian Gillis said

at 12:32 pm on Feb 14, 2016

Page checked

Martyn Clarke said

at 9:28 pm on Jan 28, 2017

OK I will own up. I was working in Manchester at Granada TV in 1965. It was a Sunday morning and we had just moved into a flat in Didsbury.
I didn't know where the paper shop was so turned right into Palatine Road (during the week you were lucky if you could do 15mph) I saw a Rover P4 parked up with someone reading a paper, next thing I know I am pulled over, I saw PETA sitting on rear parcel shelf. I get into the Rover and handed over my licence the cop read it and said "my heart bleeds for you but I am still going to b---dy book you. The reason was I had just come back from 3yrs installing studios at Radio Ankara Turkey and the address in my licence was c/o Marconi New Street Chelmsford!! I did ask to check the calibration. Anyway that cost me £5 but it was NOT down as that on my expenses.

I borrowed a PETA when I was clerk of course on a Chelmsford Motor Club Britvic Rally, to check it I set it up on the Roxwell Road and 1st car through was a Police car probably saying WTF ! It had desired effect keeping speeds down in villages en route.

I saw a PETA up in Scotland during the Scottish Rally we were servicing on, we made up a sign which said Hello PETA when we kept spotting it.

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