GPS tracker/12v interference question

[benrosenick]

Hi, I bought one of these GPS trackers from ebay. It has an internal battery that they reckon will last for 60 days, as well as a 12v connection to keep it charged. It seems to work pretty well; has all of the usual features and was easy to set up - but... when plugged into a 240v power source with the provided adapter it is perfect, but when I connect it direct to 12v, either through the cig plug adapter or using the harness straight to the battery, I hear the GPS signal every time it handshakes with the GSM network (if you know what a mean, the dit-dit-dit-dit-dit-dit noise...). I know there isn't a speaker inside it, and I am certain that the noise is coming from the device itself and isn't interference through my speakers. The supplier has said they don't know what it is and haven't heard of it before, and how can it make a noise if it has no speaker, but its does!!

Does anyone have any idea what the cause may be, and if so what can I do to prevent it? I don't understand why it only happens with a straight 12v input, as opposed to 12v via transformer (it is even fine if I use an inverter to go 12v ->240v ->12v!)


Thanks, Benrosenick

 

[Gadgets 21.63.1]

is there anything else that can emit the sound, radio turned on, uhf, or anything else. the noise could be coming from there, as the noise would travel but up the dc power cable to another audio device. ??

 

[Gadgets 21.63.1]

just had a read of the item on there website, you are right there is no speaker, only microphone. so the noise would be coming from something else in the van that is turned on. you would have to run its own power lead from the battery, also might have to put a 12 volt power filter, simular to what is found on the back of a car radio, this will filter out any noise that would be going back up the power cables. normally running your own power lead direct to the battery would stop any noise.

 

[relgate]

Could it be coming from the microphone? They are essentially the same device as a speaker...

 

[Gadgets 21.63.1]

hello, these days they use a condenser type micro phone, basicly nothing like a speaker at all. so not from the microphone. if the sound is coming from the device its self, then maybe coming from a filter coil inside the unit, that could make the noise, but it would have to be very bad quality unit to do that. i would start by connecting the unit direct to the battery and see if the noise go's away. (fyi. i used to be a tech in a r&d electronics department years ago). however as this unit is chinese made, it could have a redundent speaker on board not being used for this software running this device. I am going to purchase one of these units and build it into a very small box and use it for a dog tracking device for when we are free camping on rivers as such. so i'll let you know about these noises that you are hearing, as i will be opening the unit up.

 

[benrosenick]

Thanks all, the noise definitely comes from the device. It is connected directly to the battery posts at the moment, but also makes the noise if I use the 12v plug and plug into a 12v accessory socket which is obviously on the other side of the setec box as well. I might take it out again this weekend and connect it to a spare battery away from the van and see if it still does it...

 

[Gadgets 21.63.1]

you have a strange one there, so i guess there is a speaker inside or noisy device inside somewhere. why it does it only on battery is strange, as the power adaptor would normally be the noisy part of the chain.

 

[benrosenick]

I agree, it is odd. The guys I got it from have been good so far and have sent a video I took of it making the noise off to the manufacturer, and they aren't that far away ion Sydney so I will take it to them to have a look at if the problem is still there with a completely separate battery.
Worst case I can put a switch in the 12v so I can turn the power off when we're in it; even if I forget to turn it back on again the battery in the GPS itself lasts for a couple of months and alerts you before it goes flat so will still have the thing active if needed.

 

[benrosenick]

Well, I have just taken it out and tried with a 12v bench supply and also a standalone 12v battery and it still makes the noise - so the good news it is nothing to do with the wiring in the Expanda.

 

[icetechaus]

Try removing your mobile from the area. It could well be the charging circuit on the GPS is running at the same frequency as your phone. It won't solve your problem long term but could hep to pinpoint the issue for the manufacturers.

 

[benrosenick]

Try removing your mobile from the area. It could well be the charging circuit on the GPS is running at the same frequency as your phone. It won't solve your problem long term but could hep to pinpoint the issue for the manufacturers.

Thanks @icetechaus, just tried it with the mobile remote from the GPS and it still makes the noise - but also still only when connected to a 12v power source. I'm stumped...

 

[benrosenick]

Finally got a reply on this

'Engineers tested TK104 for the noise, most TK104 have light noise. only if you put the device near GSM devices, you can hear the noise. Noise comes from the GSM antenna frequency and the charging frequency. Engineers are trying to improve the noise problem, but now , it is cannot change this situation.'

So there is an issue, but they can't fix it (and it happened when the device isn't near a GSM device as well...). I am probably going to keep mine and add a switch so I can turn off the 12v easily when I am in the van, but may be worth considering if you are looking at one of these (this was the TK104 model)