# [EVDL] Re ducing radio interference?



## EVDL List (Jul 27, 2007)

I found that in many metal body vehicles, that the body is use as a ground 
return to the battery, which could be a high resistance path and even cause 
some capacitance reactance across some bonding of the metal.

I notice this when I dissemble my vehicle and had all the panels and 
fittings epoxy painted. Instead of remove the paint off each grounding 
point that the device was using a ground for, I ran a grounding buss system 
starting at the 12 volt battery and runs completely around the inside 
perimeter of the motor bay, the passenger compartment and the rear equipment 
bay.

This is sometimes known as a counterpoise grounding system, where the ground 
buss rounds in a complete circuit and both ends connect together at a 
junction point.

I use a insulated No. 1 AWG stranded copper wire that terminates at each 
grounding point using a brass bolt coupler that screws in a body point, 
using a star washer which acts like a standoff. The ground buss wire is 
connected to each standoff using a terminal lug. Tap off from each ground 
point then goes to the device that require a ground.

If the device has a metal enclosure, than the enclosure is also grounded to 
this ground buss system. Do not relied on the enclosures to self ground it 
self to the body of the vehicle.

If the enclosures are large, I will ground these enclosures at both ends of 
the enclosures. For a electrical ground, I will run these as a separate 
ground buss or even separated ground circuits back to the a large 
junction/terminal block as close to the 12 volt source as possible.

I also using separate ground circuits to the motor control, alternator, 
inverter, and to the instruments in the console and dash.

The most important thing, is to have a good ground to the frame of the 
motor. My first EV motor mounts and transmission mounts isolated the motor 
from the ground frame. The only path to ground was though the driveline to 
the differential which cause a lot of static.

So I install a large 2/0 ground cable to the motor that runs directly to a 
large terminal power block where the ground buss ran to.

The radio I have is a Sony unit that is metal case, which slides into 
another metal case in the console. Both of these cases are electrical 
ground to a grounding buss that runs directly to the negative 12 volt 
battery, not the chassis bonding grounds.

The speaker wires are double shield with the internal shield floating, and 
the external shield grounded to the external metal housing. The speakers 
are not in the dash or doors, rather are mounted in a speaker bar that is 
normally use for pickups just behind the seats which are mounted on the 
steel firewall.

My AM now only gets noise when I first press the accelerator to start 
moving, then after that there is no AM noise. I never had any FM noise with 
the mod.

Roland




----- Original Message ----- 
From: "Rob Trahms" <[email protected]>
To: <[email protected]>
Sent: Sunday, October 11, 2009 8:08 AM
Subject: [EVDL] Re ducing radio interference?


>
> Hi all -
> No drive issues with my EV Cabriolet (Voltsrabbit) conversion, but I 
> wanted
> to check with the group on a minor issue. During driving, my AM/FM radio 
> is
> essentially worthless with the amount of static my system is generating
> (confirmed that when I am not driving, there is no radio interference).
>
> Interestingly enough, I can use my iPod connected to the stereo just fine
> during driving, no static.
>
> I am pretty sure this must be a common problem among EV'ers.
>
> Any simple solutions out there? Is it typically a magnetic phenomenon 
> from
> the motor, or is it coming in through the vehicle ground? Can I suppress
> the noise on the radio end, and if so, how?
>
> Thanks,
> Rob
>
>
> -----
> Rob Trahms
> [email protected]
> Electro - the Cabby-EV
> http://chaosmgmt.blogspot.com chaosmgmt.blogspot.com
>
> -- 
> View this message in context: 
> http://www.nabble.com/Reducing-radio-interference--tp25844182p25844182.html
> Sent from the Electric Vehicle Discussion List mailing list archive at 
> Nabble.com.
>
> _______________________________________________
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>
> 

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## EVDL List (Jul 27, 2007)

It depends on what is generating the RF noise and how its getting into your 
radio. Your iPod doesn't utilize the AM/FM radio front end which says the 
problem is Radio Frequency noise getting into your radio either via the 
antennae, power or ground and not audio frequency noise. If the noise were 
audio frequency and getting into the 12V/GND system, the iPod would likely 
suffer also. You could try some experiments to see if its being transmitted 
and entering your antennae or leaking into your radio via some other route. 
If its going the RF route, you need to suppress it via its source. If its 
leaking into the 12 volt battery and ground, you can put a filter on its 
power input. If its getting in via some ground route, you probably will also 
need to stop it at its source.


You need to isolate the :

source(s) Motor, controller, etc..
paths(s) GND, +12V to GND, transmitted RF
signal character RF or Audio
How it gets into the radio - RF through antennae, RF through GND/12V or 
both, RF through grounded metal


Two branches in tracking it down are 1) isolating the radio and 2) Faraday 
shielding http://en.wikipedia.org/wiki/Faraday_cage the source.

1) If you can get to the coax that goes from your radio to the antennae, 
then disconnect it and try first terminating it to isolate:

Is it getting into the actual antennae that the signal is entering ( 
terminate the coax or extend it 50 feet from your car and see what happens) 
OR
Is it getting into the radio RF front end via power or ground or both? If so 
then an LC filter between the +12V battery -> radio might help or

Temporarily power your radio from a battery outside your car. Disconnect the 
radio +12V ( if you can) and use a battery much like you would when jumping 
the car except connect GND->GND and +12V -> radio. That eliminates the +12V 
as the path.

Make sure all the EV components are properly grounded. Then try and build a 
Faraday Shield http://en.wikipedia.org/wiki/Faraday_cage around each 
component ( motor, controller etc.. ) one at a time while listening to the 
radio. If you shield the actual source with temporary cage and it stops the 
noise, you know the source and the path.

Once you know the source and path, you can decide whether to discuss it with 
the supplier of the offending part or shield it.

You also might try pulling another car alongside your EV and see if its 
radio hears the noise. If it does, and its bad, the path is probably RF 
through the air. If it doesn't, then the path may be RF via +12V and GND. 
That's an easy quick test. Get a small battery powered radio and place it 
near each possible component. If its RF, then the battery powered radio will 
behave similar to your EV car radio.

If you are lucky, then its one part via one path and easy to find and fix.

If you are not, it could be multiple parts as sources and multiple paths and 
it will be a bummer.

Does any of that make sense?

Tom

.



----- Original Message ----- 
From: "Rob Trahms" <[email protected]>
To: <[email protected]>
Sent: Sunday, October 11, 2009 8:08 AM
Subject: [EVDL] Re ducing radio interference?


>
> Hi all -
> No drive issues with my EV Cabriolet (Voltsrabbit) conversion, but I 
> wanted
> to check with the group on a minor issue. During driving, my AM/FM radio 
> is
> essentially worthless with the amount of static my system is generating
> (confirmed that when I am not driving, there is no radio interference).
>
> Interestingly enough, I can use my iPod connected to the stereo just fine
> during driving, no static.
>
> I am pretty sure this must be a common problem among EV'ers.
>
> Any simple solutions out there? Is it typically a magnetic phenomenon 
> from
> the motor, or is it coming in through the vehicle ground? Can I suppress
> the noise on the radio end, and if so, how?
>
> Thanks,
> Rob
>
>
> -----
> Rob Trahms
> [email protected]
> Electro - the Cabby-EV
> http://chaosmgmt.blogspot.com chaosmgmt.blogspot.com
>
> -- 
> View this message in context: 
> http://www.nabble.com/Reducing-radio-interference--tp25844182p25844182.html
> Sent from the Electric Vehicle Discussion List mailing list archive at 
> Nabble.com.
>
> _______________________________________________
> General EVDL support: http://evdl.org/help/
> Usage guidelines: http://evdl.org/help/index.html#conv
> Archives: http://evdl.org/archive/
> Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev
>
> 


_______________________________________________
General EVDL support: http://evdl.org/help/
Usage guidelines: http://evdl.org/help/index.html#conv
Archives: http://evdl.org/archive/
Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev


----------



## EVDL List (Jul 27, 2007)

I thought we were supposed to keep the motor isolated? So this says to 
ground the motor case to the car. Never thought of that. What happens 
if I don't have it properly grounded? Static or other dire things?


Pete 



> Roland Wiench wrote:
> 
> > The most important thing, is to have a good ground to the frame of the
> > motor. My first EV motor mounts and transmission mounts isolated
> ...


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## EVDL List (Jul 27, 2007)

The motor enclosure ground is from the 12 volt ground, not from the battery 
pack. The motor case is getting some type of high resistance ground through 
the transmission, drive line and differential. As these unit rotate, you 
can get a static build up in these units.

In our electrical work, we always shunt movable and rotating joints with 
heavy grounding wires to reduce the static and/or capacitance reactance.

If you connect a speed sensor to the motor which has a tiny ground conductor 
that is connected to the motor chassis, this wire will and has build up in 
static so much, that it interfere with the speed sensor circuit. To reduce 
this static, I had to install a larger ground wire to the motor to reduce 
this static.

This also reduce any interference on temperature sensors that is connected 
on and in the motor which required a 12 volt ground path return to work.

If you have a transmission with electronic sensor and speed control, this 
also requires a 12 volt grounded return.

Roland


----- Original Message ----- 
From: <[email protected]>
To: "Electric Vehicle Discussion List" <[email protected]>
Sent: Monday, October 12, 2009 7:07 AM
Subject: Re: [EVDL] Re ducing radio interference?


> I thought we were supposed to keep the motor isolated? So this says to
> ground the motor case to the car. Never thought of that. What happens
> if I don't have it properly grounded? Static or other dire things?
>
>
> Pete 
>
>


> Roland Wiench wrote:
> >
> > > The most important thing, is to have a good ground to the frame of the
> > > motor. My first EV motor mounts and transmission mounts isolated
> ...


----------

