Question about ground loop interference

[mr_magicfingers]

Fitted to my 1150gs I have a bike powered autocom along with a bike powered kenwood radio and a bike powered iphone which I use as a satnav and ipod.

I have a secondary fuse box powered via a relay straight from the battery. The autocom, radio and ipod are all powered from the same fuse on the fuse box with common positive and ground connections.

Why do I still get ground loop type interference, everything's got the same power path? I thought you got the interference due to different ground paths for the different devices but in this case they're all the same.

I bought a cheap ground loop eliminator from ebay but found that it wasn't very good, and cut the volume dramatically and also the quality of the music. Bought a better known brand unit and fitted that, it also cuts the music volume dramatically and certainly takes the sparkle off the music. I'm assuming this is just a function of the device and they'll all do something similar including the autocom unit.

I set up everything so that I didn't think I'd have any of these issues. Can anyone explain why I still get the interference please.

Thanks,

J.

 

[Engineer]

Fitted to my 1150gs I have a bike powered autocom along with a bike powered kenwood radio and a bike powered iphone which I use as a satnav and ipod.

I have a secondary fuse box powered via a relay straight from the battery. The autocom, radio and ipod are all powered from the same fuse on the fuse box with common positive and ground connections.

Why do I still get ground loop type interference, everything's got the same power path? I thought you got the interference due to different ground paths for the different devices but in this case they're all the same.

I bought a cheap ground loop eliminator from ebay but found that it wasn't very good, and cut the volume dramatically and also the quality of the music. Bought a better known brand unit and fitted that, it also cuts the music volume dramatically and certainly takes the sparkle off the music. I'm assuming this is just a function of the device and they'll all do something similar including the autocom unit.

I set up everything so that I didn't think I'd have any of these issues. Can anyone explain why I still get the interference please.

Thanks,

J.

The ground wires are a finite length with finite impedance, they travel in a hostile electromagnetic environment and will pick up noise.

The signals are single ended so any currents induced into the screens will appear in series with wanted signal. The only sure-fire way to almost eliminate noise is to use differential signalling - like that used in professional audio.

There are many factors that determine the amount of noise pick-up, (i) the quality of your screened cables - one often can't tell how well the screens are terminated (ii) the cable routing, i.e. is it close to a noise source (iii) the problem might not be with your audio cables, it could be that you have an excessive noise generator on your bike because of poor design or wiring etc, etc, etc, etc.

Good luck!

 

[mr_magicfingers]

The ground wires are a finite length with finite impedance, they travel in a hostile electromagnetic environment and will pick up noise.

The signals are single ended so any currents induced into the screens will appear in series with wanted signal. The only sure-fire way to almost eliminate noise is to use differential signalling - like that used in professional audio.

There are many factors that determine the amount of noise pick-up, (i) the quality of your screened cables - one often can't tell how well the screens are terminated (ii) the cable routing, i.e. is it close to a noise source (iii) the problem might not be with your audio cables, it could be that you have an excessive noise generator on your bike because of poor design or wiring etc, etc, etc, etc.

Good luck!

Ah, thanks, that makes much more sense now. Running balanced cables and connecting everything with xlr connectors would certainly raise a few eyebrows Will just have to live with it or lower volume.

Cheers,

 

[roddy]

would twisting together long runs of cable not help with the interference, as the noise would cancel out to a degree ? roughly a full turn for every 20ish cm of run

I'm thinking of network cabling here thats twisted pair cabling and it's this way to help reduce interference pick up on long runs of cabling

 

[SilverFish]

I bought a cheap ground loop eliminator from ebay but found that it wasn't very good, and cut the volume dramatically and also the quality of the music. Bought a better known brand unit and fitted that, it also cuts the music volume dramatically and certainly takes the sparkle off the music. I'm assuming this is just a function of the device and they'll all do something similar including the autocom unit.

I had similar results after making my own isolator from components bought from Maplin. I replaced it with an Autocom part and it was much better overall.

My old 1150 had lots of interference though whatever I did, subsequent bikes have been much quieter.

How have you set your iPhone up, to keep it dry and still useable? I've just got one and am loving it after years of dissapointment with Windows Mobile. Interestingly, I have now managed to get a decent DAB/FM radio working on a bike by using a Roberts Robi attached to it. The first time I've managed to do this after dozens of attempts with different FM radios from all over...

I also replaced the Maplins 3.5mm audio cable bought to link the Robi/iPhone to the Autocom again with the Autocom (non isolated) music lead. I didnt think it would make any difference - just tidier jacks, but the shielding is better it seems.

Mike

 

[mr_magicfingers]

I had similar results after making my own isolator from components bought from Maplin. I replaced it with an Autocom part and it was much better overall.

My old 1150 had lots of interference though whatever I did, subsequent bikes have been much quieter.

How have you set your iPhone up, to keep it dry and still useable? I've just got one and am loving it after years of dissapointment with Windows Mobile. Interestingly, I have now managed to get a decent DAB/FM radio working on a bike by using a Roberts Robi attached to it. The first time I've managed to do this after dozens of attempts with different FM radios from all over...

I also replaced the Maplins 3.5mm audio cable bought to link the Robi/iPhone to the Autocom again with the Autocom (non isolated) music lead. I didnt think it would make any difference - just tidier jacks, but the shielding is better it seems.

Mike

I've used an old ram mount that I had lying around and an iphone bracket for it. I took the screen off and the lower silver headlight cover, drilled two holes and mounted the ram mount with big washers backing it up. Brought the audio lead up underneath it as you can see in the photos.

Not shown but since installed, I bought a car adapter from ebay for a couple of quid, took the little circuit board out, soldered on a power cable and then fitted it into a little plastic container that used to hold sewing thread, stuffed it full of hot melt glue and then wrapped the container in self amalgamating tape.

That lives under the silver panel too with just the power lead coming out on the other end of the phone.

So far I haven't used any weather protection, it's under the windscreen and that seems to keep it nicely out of the weather.

Ultimately I'd like a garmin zumo, but that's a little way off yet. In the mean time, the biologic bike mount for iphone looks like being a good bet, if I could mount it to the ram mount the same way. That would give it full weather protection.

To use the iphone on the move I put a few tacks of conductive thread through the end of my summer glove, which is what I use most of the time as I have muffs on the bars over the winter, you can see the mod here.

Hope that helps

 

[SilverFish]

Thanks for the info.

Thinking about it a bit, as I already have a Zumo, I'll probably stick with that for satnav and the iPhone for choonz/phone as the do a much better job separately I think.

Cheers,

Mike

 

[mr_magicfingers]

Thanks for the info.

Thinking about it a bit, as I already have a Zumo, I'll probably stick with that for satnav and the iPhone for choonz/phone as the do a much better job separately I think.

Cheers,

Mike

Oh if you have a zumo then definitely go that route. The iphone isn't that great as a satnav, it has issues but was a cheap option for me for the moment as I already had the phone. If you have a 3gs then you can bluetooth to the zumo and have voice control of the iphone if you have an autocom or other bluetooth headset. Much better in my view and the route I will go eventually.

 

[advancedbiker]

Stick with the Zumo I'll go for that

I fitted the type of battery ground loop device from E Bay, but it failed after 12 months. I bought the Autocom lead and it works as well, but I have always suffered from low volume. I went down and saw Doug from Autocom and he did a tweak on the Autocom vloume output. Works great, running MP3 from Zumo 550 at around 40 % for most road speeds.

Great system

 

[Engineer]

would twisting together long runs of cable not help with the interference, as the noise would cancel out to a degree ? roughly a full turn for every 20ish cm of run

I'm thinking of network cabling here thats twisted pair cabling and it's this way to help reduce interference pick up on long runs of cabling

Network cables are differential signalling - wires are twisted to ensure that interference is the same on both wires so that common mode signals are taken out by the differential receiver

Audio signals are normally singled ended so this won't work! what you need is a good screened cable and single point grounding system.

 

[sanqhar]

Have you tried powering the devices from different fuses on the fuse box?

This is how I have my Zumo and Autocom wired to my Centech and I have no ground loop problems.

tom