 Has anybody else noticed this effect? It would be useful to know how common it is. It is more likely to affect tiller pilots, where the compass is likely to be close to the pocket containing the mobile, than wheel pilots, where the compass is likely to be hidden away from the cockpit.
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In my Windy 37 Motor Cruiser we always travel with the mobiles on the dashboard. We have a Raymarine RL80 combined with a ST 6000 autohelm and have had the same experience of the boat under autopilot without warning taking a violent course change for no apparent reason (quite exciting at 30 knots). We have also noticed on the chart plotter, without the autohelm engaged, that the boat position symbol spins in a clockwise direction. Having had a sotfware upgrade on the sytem last year this not seem to occur so regularly and having spent much time ensuring that there is no metal close to the fluxgate compass (and spending out on a new one) the mobile phone effect may well be the answer. I look forward to giving it a good test.
SRT
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 Two of us have had this unexplained problem. My cousin has an autohelm control box mounted on the cockpit face. Inside the saloon is a shelf where he keeps his mobile some 60 cms away. I have a tiller pilot and every now and then the mobile is in my pocket. David Evans may have stumbled across a revelation. What do Raymarine/Simrad say?
DMH Du B
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 | TMS Poloshirt winner |
12/04/07 14:34
 Well in my now elderly sharp autopilots manual it warns of anything electrical/cables nr.the sensor -a no go area of at least 3 ft.-also warns of having sensor near any other compass etc.
Also in case of power boat/motor sailor proximity to windscreen wipers/any other type of electric motor?-and mobile phone signals can be heard interfering with radio at home!Then there is the interference that can be generated by the engine alternator.
Whether these can effect modern computer controled systems I do not know.
Phil
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 Yep We hav experienced the same thing in our Atlantic 44 that we use for RYA courses. We also suspected mobile phones were was responsible and now suggest that mobile phones are kept well away. Melody
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I have an raymarine 6000 autopilot on my Beneteau and have had numerous occasions when the boat has done a right angle turn when under autopilot but have identified one place in the menai straits where whenever the boat is within about a half mile of a shore transmitter mast, it always happens.If I leave the autopilot on standby in this position, the feedback from the fluxgate compass swings wildly by more than 30 degrees which obviously would cause the boat to alter course if under "auto" control. This does not account though for the times that this has happened in the middle of the Irish Sea out of range of mobile mast transmissions but gives me ideas to try. Dave Calvert
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| TMS Poloshirt winner |
02/10/08 18:57
I have noticed the radio transmitter at Orford Ness do the same, but thay even make GPS plotters & echo sounders go all peculiar as well! God knows what they are transmitting!
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| TMS Poloshirt winner |
02/10/08 19:51
Sure its not the switching system on control motor thats sticking?-on my old Sharps autopilot this was a problem-reversing electric motor which in my case controls hydraulic pump is switched by electro mechanical relays-these through wear randomly would stick-result when a course correction was made motor just kept going putting rudder full over and bypassing electronic control unit. Phil
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I do not think that is the problem in my case but sticking relay contacts would cause a correction to continue. When I am in the area of the transmitter I mentioned, I can monitor the fluxgate compass feedback that shows on the display unit (which becomes the setpoint when engaging auto) until it settles down at about a half mile from the transmitter and it then controls with no problems. I have the master unit by the chart table and the repeater on the binnacle and I usually leave my mobile on the table, so I will do some tests to see if this can also affect the performance. Maybe rewiring the autopilot in screened cable might be a cure?
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Hi David. I sympathise with the problem. The BBC World Service transmitter at Orfordness has caused our electronics a lot of grief over the years. Usually you can make them better by recalibrating them, but a couple of years ago it completely fried our windspeed/direction instrument. Raymarine advised fitting more ferrites, if that is any help! (So far, touch wood, the replacement unit has survived passing Orfordness. At least it is only the World Service there now. A few years ago there was a Decca mast (which seemed to upset yacht Decca) and the Americans' top secret over-the-horizon radar array as well! Wonder we even survived passing close inshore....
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| TMS Poloshirt winner |
03/10/08 13:41
 The output of the 1296 kHz mast totals 3.15 megawatts of power output, a fixed VHF is usually 25 watts maximum. I think the compass safe distance for a VHF is usually 1.5 metres - do the maths and it's no wonder it causes problems. Some info here: http://tx.mb21.co.uk/gallery/orfordness.php. What didn't interfere with Decca? Have you checked to see if you glow in the dark Cathy?!  W.
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