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Old 20 December 2010, 15:21
Certa Cito Certa Cito is offline
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inductive loops and earpieces

Hopefully one for the 18E types in here.

Anyone here got experience with covert communications in vehicles? Specifically using an inductive loop and wireless earpiece. I'm experiencing a hell of a lot of interference in the earpiece, particularly when the vehicle's running, which is of course to be expected, and was wondering if any of you have experience in this scenario?

I've put a DC power filter in the circuit specifically for the radio, and that's as much as I can think to do. I know that this is not a totally interference-free system to use, but surely there must be some way to increase the sound quality?

I have done a brief Google search, but this is of course quite a specialised application of technology that we're more used to seeing in cash machines and public amenities, which is why I've asked here, other than in more civilian-orientated forums.
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Old 20 December 2010, 15:34
diverescue diverescue is offline
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WAAAY out of my lane, but you may consider some high quality "noise supression" or "radio supression" spark plug wires. I know with A.M. radio they make a HUGE difference in electronic interference.

back to the lounge...

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Old 20 December 2010, 15:43
Certa Cito Certa Cito is offline
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Thanks for the reply.

Never even heard of doing something like that. I know enough about cars to keep them moving, but other than that, nothing. Perhaps for that reason, I hadn't thought of doing anything to the vehicle itself, just figuring that it is something I'd have to live with, and counter its negative effects by adapting the communications system.
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Old 23 December 2010, 00:55
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spectr17 spectr17 is offline
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Spark plug interference usually sounds like clicking. A whine that rises and falls with motor RPM is usually alternator related. You can try a different brand DC filter or move the ground wire of the device in the vehicle to another location. Also make sure you have a good metal to metal contact on your ground. Running the ground back the battery can sometimes cure the interference.
Some days its just not worth chewing through the restraints
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Old 23 December 2010, 08:02
Certa Cito Certa Cito is offline
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Sounds more like the alternator that's causing it then. Funny thing is, it's worse in German-made cars, such as Volkswagen, Audi, Seat, etc. The ground almost always runs back to the negative terminal on the battery, although I have come across a few where this isn't the case. I'll find out about maybe getting a different type of filter, although I have no idea as to what the characteristics of the current ones are. I'd have to imagine that they're the best I can get though, as they were made bespoke by a company that we deal a lot with for this sort of thing.

I have got a funny feeling though that we'll just have to deal with it. Comms are workable, but I would just like to try and improve them, of course. However, this isn't a new problem, and has been like it for years, so if no-one has done anything about it by now, then maybe nothing can be done?
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Old 23 January 2011, 10:45
kollkash kollkash is offline
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a LITTLE interference is expected; however, when I worked with vehicle inductor loops (while wearing a personal inductor loop, too), it was never an issue. If you know anyone across the pond in the UK, they have it down to a science with their installations. I remember having a slight hiss (nothing major) and I could even have the local radio on without any effect. I realize this might not help you specifically--I just want you to know that it CAN be done. If I find anything more, I'll post. Good luck.
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Old 11 February 2011, 11:20
hdjohn hdjohn is offline
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I'm sending you a pm...........

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