South Essex Amateur Radio Society

© SEARS 2010 Webmaster Dave Speechley G4UVJ...Last update 23 Mar 2010

Radio Direction Finding is a well established technique, used for decades as a form of nautical and aero-nautical navigation. It is used to locate clandestine transmitters and has a regular following in Amateur circles, where it is referred to as “Sport Radio”, or more commonly Fox Hunts.  Contestants are required to locate several low power hidden transmitters in rough terrain or woods etc. using a combination of RDF and orienteering. Interference to any form of wireless electronic communications, broadcast, 2 way radio, TV, and telephones may also be traced with RDF. This is an account of how it has been put to practical use, to locate interference on the 433.500MHz FM Calling Channel (U280).

Following installation of a new 6m/2m/70cm triband co-linear antenna at my Canvey Island, Locator JO01HM, home I discovered a continuous pulsing S7 signal on U280. Curious about the strange signal I fed it into my laptop PC, running Skysweeper Signal Analysis/Decoder program. Having monitored with Skysweeper round the clock for several days the following observations were made about the signal:

• Continuous (24hrs)

• Pulsed

• Amplitude Modulated

• Vertically Polarised

• Varying signal levels

• Varying pulse widths

• High Level & Low Level Signals are interleaved

o Rally 2009    Click on images to see Lar

gClick here to play a recording of the above.

I made some CQ calls on S20, the 2M FM calling frequency, 145.500 MHz, for any known information about the racket on 433.500 MHz. I received a mixed response. There were those who don’t use 70cms, declaring it as a waste of time. There were those who received the interference but were advised that nothing could be done about it as the band was shared and hams were secondary users. Some could not receive it and others were reporting S9+30 dB. There was also the senior know-all, the source of mis-information, who had claimed he knew all about it from an acquaintance, insinuating the source was MOD and it was all hush-hush and that questions must not be asked!  The one useful piece of information I did glean was that the interference was far worse in Essex than in Kent. This could be due to topology or a signal directed northwards.      

By Weds 12th November 08, having analysed the signals I decided to contact Ofcom’s Amateur Radio Licensing Dept. I relayed the audio over the landline but they could offer no explanation so full details were taken and Complaint Ref: 1-69814043 raised.

On Tues 18th November 08 , Ofcom’s, Ian Crompton and a colleague visited the M0FZW QTH where they were able to hear the signals and see the graphic Skysweeper display. Intrigued they set off to DF the signals, starting on the south Canvey seawall. Later that day Ian called with an update. He had traced the signals to the eastern side of the Isle of Grain, Kent, suspecting the Liquid Nitrogen Plant. However he could not gain access without prior arrangement. By Tues 9th December 08 all the Liquid Nitrogen Plant remote valve control equipment had been turned off but the signals remained.

From the outset I had been relating the tale and events to SEARS members on our regular 145.225 MHz net and was considering a bit of DF’ing myself. Peter, G4OAD, Locator JO01GO, 27 miles, as the crow flies, from the Grain site, was also receiving these signals, and was likewise intrigued about the source. We decided to team up and have a go during the Christmas break.

On a bright but bitterly cold December 30th 2009 M0FZW & G4OAD teamed up and armed with my FT-847 and a hastily home-brewed 4 element yagi went out to trace the source of interference. Bearings were taken at Leigh, above the Alexander Yacht Club; 163°M, and Shoebury East Beach; 195°M. Later another was taken from the Lobster Smack, Haven Rd, Canvey Island; 130°M.  Plotted on OS Map 178 they formed a “cocked hat” in West Swale, Kent. We drove to Sheppey, Kent for more bearings. Iwade: 35°M and Kingsferry Bridge 50°M (beaming under the Iwade to Queenborough bypass). These pointed directly at clearly visible navigation beacons in West Swale. However cold and failing daylight beat us

The following day a call to the Sheerness Coastguard verified that the West Swale beacons are only lights, with no radio, so suspicion moved to a solar powered weather station on the new Iwade bypass. This is a new modern bridge, similar in style, but smaller, to the QE2 at Dartford.

On Friday 2nd Jan 09 I emailed the Highways Agency requesting information, under the Freedom of Information Act 2000, regarding use of equipment on or about 433.500 MHz. A reply was received a week later, “The Highways Agency has no radio equipment transmitting on the frequency of approximately 433.500MHz at the location you asked about.”

Having drawn a blank I contacted Phillip Boorman, G0JBA, Swale A.R.C. Hon Sec. and explained the situation. Coincidently he has worked on Kingsferry Bridge and has detailed knowledge of the Swale area. He was aware that trains approaching Kingsferry Bridge send data channel pulses every 11 sec's on 454.856 MHz. He offered to find out about other bridge equipment.

On Sun 11th Jan 09 I received an informative email from Phil, G0JBA. He had taken bearings from his Ashford QTH, Locator JO01KD, with a 24 element yagi and found two signal peaks at 17°M; 433.500 MHz (S4) and 433.505 MHz (S3). These point to the MOD mast at Dunkirk Hill (off A2).

On Tues 13.01.09, 10.00hrs Ofcom’s Ian Crompton called. He has located a 433.500 MHz user at Perry’s Farm, adjacent to B2001, leading to Isle of Grain Power Station. Apparently this user has approval for use of this frequency up a max E.R.P. of 1mW for continuous or 10mW intermittent use.

On Sun 18.01.09 Phil, G0JBA traced the strongest signal received at his Ashford QTH, (JO01KD), bearing 17°M, to a farm located adjacent to the A28 between the village of Wye and Chilham. At Boughton Hill, near the A2, between Faversham and Canterbury, he received a S9 signal at 284°M. Plotted on an OS map this passes directly through the Isle of Grain Power Station site. He also received a S3 signal at 15°M from near Detling Hill (700ft asl) on A249, between Maidstone and Sittingbourne.

Both Ofcom and us Amateurs have bearings that pass directly through Perry’s Farm, Isle of Grain.

 Leigh: 163°M (by M0FZW & G4OAD)

Detling Hill:15°M (by G0JBA)

OK so what exactly is the source of the problem?

A wireless Tower Crane Anti-Collision System or Crane Avoidance System installed on the 3 cranes in the left of the picture being used to construct huge natural gas storage tanks at Grain LNG. There are several manufacturers of this type of equipment designed for use where more than one crane is operating in close proximity. In this case the French SMIE system was being used.  

Basically control software is programmed with the construction site boundaries and with each cranes parameters so that “no go zones” are established. Then whenever there is risk of collision the crane is brought safely to a stop, without causing load swing. Over-sailing of critical zones and static obstacles such as high-voltage lines, railway tracks, public highways, etc. can also be prevented. There is even a black box recorder option. Clearly these are very useful safety devices but the radio control signals should remain largely within the construction site.

The defunct Radio Communications Agency published an informative document “Radiocomms for Tower Cranes: RA195”. Here it states that a “maximum signal strength at a distance from a crane, no matter which techniques are employed, shall be “a maximum of 48dB/ìv per metre measured at 2km from the crane at a height of 3 metres above ground level is acceptable.” However, it continues, “If an interference complaint is received, and the offending radio system does not conform to these parameters then it will be necessary for that system to be re-engineered so that it does conform”.

Mon 19.01.09  Ofcom called with an update. CB&I at Isle of Grain has stated that as from Fri 23.01.09 one of the cranes at Perry's Farm will no longer be used and therefore the Crane Avoidance System will be turned off. SMIE equipment at the CB&I site is operating illegally but Ofcom are prepared to let them continue until Fri.

Fri 23.01.09.  Ofcom will call me next week to confirm it has been closed down.

Mon 26.01.09, 11.15hrs. Ofcom called for an update. I report that the interference is still there. They will call back.

Thurs 5.02.09. Ian Crompton called with an update. He is having problems getting CB&I to close down the Crane Anti-Collision System.

3rd March 09

Ofcom at Grain LNG Plant. Taylor Woodrow claims they have disabled the SMIE Collision Avoidance system on all 3 cranes. The signals on 433.500MHz remains. Cranes should be off the site by 23.03.09.

Weds 18.03.09. Crane removal has begun. Signals disappearing. Cannot see the Isle of Grain due to mist and low cloud.

Thurs 19.03.09.  Checked 433.500MHz at 20.30hrs. The interference has finally disappeared. News emailed to Ofcom.

Sun 22.03.09. Mothers Day. A clear view across the Thames reveals the jibs of the 3 tower cranes have been removed.

Mon 23.03.09. Call from Ian Crompton for confirmation that all interference has ceased.

Complaint Ref: 1-69814043 is closed.

Summary

• Officially started Weds 12.11.08

• Officially closed Mon 23.03.09.

• Time taken: 131 days (3144 hours)

• Crane operator Taylor Woodrow

French SMIE Crane Avoidance System

Conclusions

Until Ofcom replaced Radiocommunications Agency in Dec 2003 the UK had the best policed radio airwaves in the world. Amongst its other briefs Ofcom was formed to deregulate, cut costs and make profit. When it took over the RA function it “released” many of the RA enforcement team of engineers and as a result lost years of experience and know-how.  It now only has a handful of fully trained Field Engineers to sort out the problems created by these changes in policy, and is currently running 2 year apprenticeships and training young people in Radio Interference skills to fill the void.

Meanwhile it can be argued that there is a need for a UK Forum and national database of EMC case history, relevant notes, and sound-bites, and analyser screen shots, where both Radio Amateurs and Ofcom can share data about interference to, and by, amateur radio. It should only contain known facts, with no bias to any party or cause.

This would be in line with our Licences:

Section 2. Terms, Conditions & Limitations:

“1. Purpose

1(1) The Licensee shall ensure that the Radio Equipment is only used:

(a) for the purpose of self training in radio communications, including technical investigations”

UKQRM , has a useful, but limited, database of sound-bites. The site is primarily lobbying against Power Line Ethernet. A worthy cause, no doubt, but with such an ulterior motive it cannot be classed as unbiased.  

As for the Grain LNG contractors and crane operators, they would never have deliberately set out to cause EMC and RFI problems. Far from it, they were only concerned with completing a massive engineering project, designed to handle 12% of the UK’s imported gas, safely and on time. Unfortunately they chose the French SMIE system which is non-compliant with the UK radio spectrum. If this situation arises again at least Ofcom and the Amateur community should now be well prepared. We have the T Shirt!

In closing, I have to say that throughout this entire investigation the exchanges between Ofcom, myself and those Amateurs and their assistants in the above account, have been one of cordial cooperation. All involved have worked together, freely sharing their skills and knowledge for the common cause. I thank them all and look forward to working with them again, should the need arise.

Norman Crampton, M0FZW.

Thames Estuary  QRM on 433.500 mhz