Shielding cables from each other and other noise

[Gremlin]

Probably comes as no surprise to those that know my BMW, but due to my slightly higher number of accessories than usual, I'm struggling with noise and feedback in some areas. Being a motorcycle, the compactness adds to the problems, ie, cables MUST run right past the alternator etc.

On UHF CB I'm apparently losing 40% of the signal end to end, one option is to replace the aerial cable with a better quality one. On GPS, connecting the mobile to GPS and GPS wired to my helmet via a comms box, there is a low hiss when in a phone call, that the other end hears. Even in normal use just by myself a variable hiss can be heard related to amount of revs (more revs, more of a hiss and vice versa).

So does anyone have some advice? I'm assuming I need to put certain cables through a shielded sleeve? Space is an issue with a lot of accessory wiring so I need a lot of shielding for not a lot of space. A quick google learn says two sets of frequencies to shield against, with differing products (foil or braid) for each. I have no idea what frequencies I have to block...

[jonbuoy]

Probably comes as no surprise to those that know my BMW, but due to my slightly higher number of accessories than usual, I'm struggling with noise and feedback in some areas. Being a motorcycle, the compactness adds to the problems, ie, cables MUST run right past the alternator etc.

On UHF CB I'm apparently losing 40% of the signal end to end, one option is to replace the aerial cable with a better quality one. On GPS, connecting the mobile to GPS and GPS wired to my helmet via a comms box, there is a low hiss when in a phone call, that the other end hears. Even in normal use just by myself a variable hiss can be heard related to amount of revs (more revs, more of a hiss and vice versa).

So does anyone have some advice? I'm assuming I need to put certain cables through a shielded sleeve? Space is an issue with a lot of accessory wiring so I need a lot of shielding for not a lot of space. A quick google learn says two sets of frequencies to shield against, with differing products (foil or braid) for each. I have no idea what frequencies I have to block...

It could be airborne from ignition/fuel injection or it could be passing through from the power connection to the bike. You could try different cable routes first. or running everything from a small battery pack instead of bike supply. If its transmitted through the power supply cable you might be able to use a ferrite or dc filter to get rid of it.

[Gremlin]

Cable routing is severely limited by the shape of the bike. Cables have to run under the tank up the frame to the front. Only have the two sides, and almost all runs up the left side. Very hesitant to use the right as the cables for the electronic suspension are there. I'd rather have audible noise than mess up the signals for suspension :confused:

Ferrite or dc filter could be possible... thanks

Just chucking this here if others are looking...
Explaining ferrites: http://www.ce-mag.com/archive/02/11/may.html

[Gremlin]

I presume these are the sorts of things to get? http://www.jaycar.co.nz/productView.asp?ID=LF1292&keywords=ferrite&form=KEYWORD

Easier to fit than this: http://www.jaycar.co.nz/productView.asp?ID=LF1250&keywords=ferrite&form=KEYWORD

[jonbuoy]

Hey Gremlin, thats the type they can make a big difference you can clip them straight over the cable or make a loop and clip the ferrite to the bottom of the loop to secure the cable. They wont help much if its being radiated through the air though. Work a go. If youve got some old vga leads kicking around there is usually one burried in each end cut them out and tape them in place for testing.

[davereid]

On UHF CB I'm apparently losing 40% of the signal end to end, one option is to replace the aerial cable with a better quality one. On GPS, connecting the mobile to GPS and GPS wired to my helmet via a comms box, there is a low hiss when in a phone call, that the other end hears. Even in normal use just by myself a variable hiss can be heard related to amount of revs (more revs, more of a hiss and vice versa).



OK, when they say you are losing 40% of your signal I'm assuming that means they have measured power out of your transmitter is (say) 5w at the transmitter and 3w at the antenna. This is the loss you would expect for 10m of coax cable not 2m, so I would start thinking poor VSWR. This is caused by a badly designed/mounted or trimmed antenna, especially one that is designed to have a good ground, and possibly doesnt have one on your motorcycle. To a power meter this looks like a large loss of power, and in fact you can usually see "reflected" power, if the meter is capable of being reversed. So start with the antenna on your CB. and make sure it is well earthed, and correctly cut to lenght if it is trimable.

Run other devices with aerial shorted out, or moved as far from the bike as possible while you listen for noise - obviously dont transmit if you have no aerial. If the noise lessens or goes away then its getting in the aerial. If its exacly the same its coming in the power supply.

Let me know what you find, there are solutions to both. cheers

Dave

[jonbuoy]

A roll of self adhesive aluminium tape is handy too, if you tape over the cables onto the frame of the bike you've pretty much made a shielded conduit. Interferance can be a PITA to find and cure.

[bogan]

In addition to what the others have said, check for ground loops first, each device should have only one ground.

[Paul in NZ]

In addition to what the others have said, check for ground loops first, each device should have only one ground.

To clarify. If you use a shielded cable you should try to ground the shield but ONLY at one end. Try to keep all grounds at the same potential so I'd suggest a common earth bar someplace directly connected to the battery earth.

I would add that running power to the devices through a relay to a clean power source is a good idea.

[banditrider]

Interesting thread although I understand very little of it :whistle:

I bought a small 12v amplifier quite a while ago and have used it plugged into my 12v acc socket, then the GPS into the amp and then onto my helmet speakers. My issue is a high pitched whine so I hooked in a filter thingee (see I'm great with this stuff) from Supercheap but this didn't fix anything.

Any suggestions for someone that should stay away from a soldering iron?

[bogan]

Interesting thread although I understand very little of it :whistle:

I bought a small 12v amplifier quite a while ago and have used it plugged into my 12v acc socket, then the GPS into the amp and then onto my helmet speakers. My issue is a high pitched whine so I hooked in a filter thingee (see I'm great with this stuff) from Supercheap but this didn't fix anything.

Any suggestions for someone that should stay away from a soldering iron?

You might have to be more specific on the 'filter thingy', if its a spin-on, I'm thinking it isn't going to help...

[banditrider]

You might have to be more specific on the 'filter thingy', if its a spin-on, I'm thinking it isn't going to help...

Something similar to this: http://www.sonicelectronix.com/item_5270_PAC-CSS-100.html

[Gremlin]

I bought a small 12v amplifier quite a while ago and have used it plugged into my 12v acc socket, then the GPS into the amp and then onto my helmet speakers. My issue is a high pitched whine so I hooked in a filter thingee (see I'm great with this stuff) from Supercheap but this didn't fix anything.

Any suggestions for someone that should stay away from a soldering iron?
Jaysus mate, I doubt I'm much better... try that Google thing, gives you heaps of knowledge you have no idea what to do with... :innocent:

Was the whine present before the amp?

Thanks to the rest of you... I'll need to digest the big words when in the right frame of mind...

[banditrider]

Was the whine present before the amp?

Nope. It's only a wee amp (12v boostaroo). Takes the volume up just enough so that it makes using the volume control on the Zumo possible - I wear earplugs so Zumo volume always at 100% and not quite loud enough sometimes...I don't want mega volume but it would be nice to have just a little more and the amp is perfect except for the "noise".

[Gremlin]

Run other devices with aerial shorted out, or moved as far from the bike as possible while you listen for noise - obviously dont transmit if you have no aerial. If the noise lessens or goes away then its getting in the aerial. If its exacly the same its coming in the power supply.
Aerial shorted out? Unplugged would work?

CB is: http://www.gme.net.au/products/radio-communications/uhf-477mhz-cb-radios/TX4600
Aerial is correct type and: http://www.gme.net.au/products/antennas/land-477-mhz/AE4001

Ground plane is hard on motorcycles, just a small metal bracket near the arse of the bike, bolted to the side of the luggage rack, just in front of the top box.

[bogan]

Something similar to this: http://www.sonicelectronix.com/item_5270_PAC-CSS-100.html

Sounds like you might have a ground loop between the devices on the audio channel, how close to the power wiring does the audio wiring from the GPS to the AMP run?

I got this effect really bad when my laptop was plugged into it's charger and mains speakers, the closer the power wiring is to the speaker wiring, the less feedback there is.

Quick check for it, plug an mp3 player into your amp at the gps end (assuming its a standard 3.5mm plug), if its ground loop, the ungrounded mp3 player won't have the whine.

[banditrider]

Sounds like you might have a ground loop between the devices on the audio channel, how close to the power wiring does the audio wiring from the GPS to the AMP run?

I got this effect really bad when my laptop was plugged into it's charger and mains speakers, the closer the power wiring is to the speaker wiring, the less feedback there is.

Quick check for it, plug an mp3 player into your amp at the gps end (assuming its a standard 3.5mm plug), if its ground loop, the ungrounded mp3 player won't have the whine.

Hmmm, that could possibly be it. From memory (I pulled everything out a while ago) I had extra length in either (or maybe both) the power supply and the stereo cable between the GPS and amp. The whole lot was then tidied up inside the glove box on the bike so it's possible everything was packed in pretty closely. Do ya reckon I should take the filter thingee outta the system?

I could also try my Ipod through it too...noise tended to change in pitch/volume with revs of the bike...

[bogan]

Hmmm, that could possibly be it. From memory (I pulled everything out a while ago) I had extra length in either (or maybe both) the power supply and the stereo cable between the GPS and amp. The whole lot was then tidied up inside the glove box on the bike so it's possible everything was packed in pretty closely. Do ya reckon I should take the filter thingee outta the system?

I could also try my Ipod through it too...noise tended to change in pitch/volume with revs of the bike...

Yeh does sound like that is the issue, the loop will be acting like an antenna and picking up interference from the coils or stator which change frequency with the revs.

I got some filters from Jaycar (http://www.jaycar.co.nz/productView.asp?ID=AA3086&keywords=ground+loop&form=KEYWORD) which fixed my laptop ground loop issues, you're welcome to try/borrow it as I don't use it anymore.

But I think the main problem is both of you guys have too much crap on your bike! I mean a glove box for gawds sake :bleh:

[banditrider]

Yeh does sound like that is the issue, the loop will be acting like an antenna and picking up interference from the coils or stator which change frequency with the revs.

I got some filters from Jaycar (http://www.jaycar.co.nz/productView.asp?ID=AA3086&keywords=ground+loop&form=KEYWORD) which fixed my laptop ground loop issues, you're welcome to try/borrow it as I don't use it anymore.

But I think the main problem is both of you guys have too much crap on your bike! I mean a glove box for gawds sake :bleh:

Oi! Glove boxes are very useful!

Cheers for that, I will have to have a muck around with it again at some stage - will let you know how I get on...

[Gremlin]

But I think the main problem is both of you guys have too much crap on your bike! I mean a glove box for gawds sake :bleh:
I would just like to state for the record I don't have a glove box!

<img src=http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=268731&stc=1&thumb=1&d=1345853370> (http://www.kiwibiker.co.nz/forums/attachment.php?attachmentid=268731&d=1345853370)

I don't think there is too much crap there... BMW put a 720W alternator in the bike, gotta be used somehow ;)

[caspernz]

But I think the main problem is both of you guys have too much crap on your bike!

Not being supportive here of course...but bogan said what I was thinking...any more farkles and you'll be in a car! :yawn::wacko:

[gijoe1313]

I've been dealing with Gremlin's unique propensity to install the kitchen sink, kit and caboodle and all manners of gee-gaws, gimcracks and whatchamacallits for ages. I do recall accusing him that his wiring requirements would rival a four wheeler with all the farkle!