 | Home > In Car Electronics > LED lightbar and communications radio issue |
 
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17353   
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Where is the light bar earthed?
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5th Jun 2023 12:35pm |
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| excossack Member Since: 22 Feb 2012 Location: North West Posts: 5842 
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Hi Tamar 11
I also have MSUK radio (Simoco with remote mount head) and no issues when keying up. But mine is fed pretty much directly from a 2nd battery via fuse box and earth direct to the battery. My aerial is mounted via a body mount over the rear door. 
As seen by the 5 mounts in the picture. Cheers John Gem 33/Gemini Recovery 1999 Defender TD5 110 Regards John M0VAZ Econet Station 48 no clock |
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5th Jun 2023 1:27pm |
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| TamarBlue11 Member Since: 25 Sep 2020 Location: England Posts: 226 
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Back to the battery, same as the radio. Thanks excossack my radio is a Motorola unit, my reversing lightbar which is mounted in the same place as yours is fine interestingly. It's just the flashing amber/red light bar on the roof (similar to ones on recovery trucks) that im having the issue with. Its one of these https://responsevehiclelighting.co.uk/rvl-...000mm.html Vendor hasn't been very helpful. |
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5th Jun 2023 2:46pm |
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| excossack Member Since: 22 Feb 2012 Location: North West Posts: 5842
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My ambers which are not on really shown on the picture are also fine with no issues. I think these have a separate earth to the radio. 1999 Defender TD5 110
Regards John M0VAZ Econet Station 48 no clock |
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5th Jun 2023 2:57pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17353
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Ah, ok. If you had said it had a local earth on the roof I would have suspected ground plane issues, but with an earth to the battery that seems unlikely. I think I'd try ferrites and making sure that there is as much separation as possible between the lightbar wiring and the antenna lead. If you can dismantle the lightbar it might be possible to fit screening to the circuitry inside, but if your bar is like mine it has been made very impossible to open using non-catastrophic means.
And there is a surprise, I don't think.  |
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5th Jun 2023 4:00pm |
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| TamarBlue11 Member Since: 25 Sep 2020 Location: England Posts: 226
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Thanks blackwolf. Yeah tried ferrite beads and routing the aerial lead down the other side of the truck.
I did think about screening as I can take it apart easily enough luckily, just wasnt sure how effective it would be. What do you reckon some thin aluminium plate? I could perhaps make a box around the main circuit board as it isn't covered currently and there should be enough room in there. |
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5th Jun 2023 6:00pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17353
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I'd give it a shot with aluminium foil, remembering that you will have to make sure that the foil doesn't short anything out. If possible, connect the foil to ground as well.
It may not work but it is cheap to try. |
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5th Jun 2023 6:42pm |
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| chopcat Member Since: 11 Sep 2012 Location: Pembrokeshire Posts: 411  
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It is caused by the RF energy transmitted by the antenna. Being close to the light bar, which looks as if it has a circuit board in it to control the different patterns, the power from the aerial, when you transmit, is activating the controls in the light bar.
The only solution would be to try to separate the two but even then you might not be able to get them far enough away depending on the power the radio is transmitting. Or you can power off the light bar from its 12v source until you need to use it. Clearly that wont work if you need to talk when on a emergency that requires lights as well! Lucky you only have a small aerial ! This one plays havoc with everything electric Click image to enlarge |
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6th Jun 2023 7:16am |
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| TamarBlue11 Member Since: 25 Sep 2020 Location: England Posts: 226
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Thanks chopcat. I did try moving it but there's not enough room on a 90 roof to separate them far enough it seems!
Do you think thinking adding a shield to the circuit board would be enough? Haha I can imagine! What do you use that for? |
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6th Jun 2023 5:02pm |
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| MadTom Member Since: 10 Sep 2013 Location: Olomouc Posts: 616  
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Screening and filtering in the problematic light is the key, because you cannot reduce the electromagnetic field strength. Ferite beads, ceramic condesators and RF chokes placed on the rigth places. This is not simple. You can try some shield over cables to the ligth, and connect it to groud on the side of the ligth or on the other side. To get the shiled, you ca remove the outer conductor from coaxial cable like RG58, for just few meter it is the cheapest way, and than slide the power cables into this shield.
EMC = electromagnetical compatibility is not simple even for professinals. Often it is lot of try and test. "Drobek" = The Small One - Discovery 2, "Blufínek" = The Blue Thing - Defender 130, and for me at least Ford Mondeo  |
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6th Jun 2023 7:35pm |
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| chopcat Member Since: 11 Sep 2012 Location: Pembrokeshire Posts: 411
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It would be worth a try although the RF energy may well be being picked up by the power cable as well so a ferrite ring with 8 turns of the power cable through it as close to the pcb would be your best bet.
Just make sure you dont short anything out ! TC |
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6th Jun 2023 10:11pm |
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| V8Simon Member Since: 17 May 2016 Location: Prestatyn, Wales Posts: 146 
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Same as John, I have a MSA radio also mounted at the rear on one of those mounts that fit on a vertical surface. Is it worth trying your ariel in a different place first to see if separation is the key? 1984 90 V8 puma want to be.
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8th Jun 2023 1:50pm |
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