Outer Limits 4x4 Board

I have fitted a HID kit to a mates Calibra, fantastic upgrade btw, he can actually see the road now... anyway, when the HIDs are on, you can hear interfearance in the FM bands, just a slight but noticable fuzz in the background, and when you get further from the commercial transmitters, like into the country, the interfearance gets more and more noticable.
What would be causing this, what could i check, anything i can fit to get rid of this?

Not present in AM or CD etc?

I thought FM is typically relatively immune to low levels of interference; I would expect an HID kit to inject noise into the power supply wiring, which I would expect to be audible in all bands / modes.

If it is FM only, I would guess antenna is the next place to look. I recall some cars had separate antennas for AM and FM (different frequencies/wavelengths.) If so, that could explain why it's only FM.

Either way, I'd start by checking all connections, particularly earth connections - a small stray resistance can act like an antenna, either transmitting noise (HID ballast) or receiving it (radio power supply wires &/or antenna earth.)

Good luck,

Scott

HID's(mainly chinese ones) have a fair amount of "noise" over FM, i have tried a few sets out and found this as well, BUT my more expensive units dont seem to highlight the issue. One thing you have to remember is there running voltage is much higher than normal and the ARC created in the tube makes electrical "noise"

G'day PJ.
I have fitted a dozen of these chinese HID's to cars and bikes.
I know of the interferance you are talking about.
It is in the ballast.
Any ballast that gave me interferance I swapped for the bike ballast as I have 4 HID's fitted( no radio ).

Should be replaced under warranty.

Al.

does the ballast have a capacitor across the supply?

Nah it doesnt have a capacitor, where and what do i put one? You use ceramics dont ya?

PJ.zook wrote:Nah it doesnt have a capacitor, where and what do i put one? You use ceramics dont ya?

Ill be honest, i dont know if this will work on a DC circuit, i know it will on AC

Im fairly certain it needs to be an electrolitic capacitot. I am not gonna dig my books out to work out what size you need, grab an 11uF one and start with that. To wire it in all you need to do it put the +leg in the +terminal and the _leg into the _ terminal on the line (supply) side of the ballast. Remember that electrolitic capacitors are polarity concious.

Frequency responses of real-world capacitors can be quite different to that of "ideal" capacitors - they don't always have low impedance at frequencies you expect them to.

If the interference is in the FM band it's around 100MHz (I'm talking orders of magnitude - it's not likely to be 1GHz, or 10MHz either.)

There's nothing wrong with trying an 11uF electrolytic, but I'm a little uncertain of how effective it would be bypassing noise around 100MHz. If it doesn't work, try some smaller values, like 1uF, 100nF, 10nF (or values in-between - this is trial and error. ) You probably won't get some of the smaller values in electrolytic, so try ceramics if necessary.

Either way, look for a cap rated to 25V - 16V can be cutting it fine for automotive applications.

Good luck,

Scott

Have had some minor success in placing sheilded cable over the high tension leads - from the ballast to the bulbs. It has somewhat helped.
This can be grabbed from most electrical places, even jaycar/RS components/Farnell Components.

Also make sure that the ballast are earthed to the chassis properly.
Not just flappin around in the breeze with a zip tie, but also with a half decent earthing/chassis wire.

Doing this should help a little bit as well.