Radio noise from Strobes

arlojanis · Post by **arlojanis** » Fri Feb 10, 2006 6:57 am

I am getting a lot of radio noise from a Signal Vehicle Products model 244 power pack and from a Star Sabre light bar. Is it best to ground the shield wire at power supply, at strobe tube, or both?

SPEAKER MIC · Post by **SPEAKER MIC** » Fri Feb 10, 2006 10:19 am

both...

if you use "hide aways" you will notice the wire has 4 conductors..

red, black, white and bare...

i grounded both ends of the "tap" line and all noise went away..

now as to lightbars, my whelen edge9000 was great against noise...

im not sure about the shielding available on them though...

also what is the distance from your antenna to the light??

that may play into it...

good luck

dbcomm · Post by **dbcomm** » Fri Feb 10, 2006 2:21 pm

arlojanis wrote:I am getting a lot of radio noise from a Signal Vehicle Products model 244 power pack and from a Star Sabre light bar. Is it best to ground the shield wire at power supply, at strobe tube, or both?

Do NOT terminate the drain wire at both ends - you'll completely defeat the purpose of the shield. Find a good solid ground as close to the strobe supply as you can, twist all the drain/shield wires together and terminate them at a single point.

nmfire10 · Post by **nmfire10** » Sat Feb 11, 2006 6:40 am

Yes, you only ground the power supply end of the cable's shield drain. Do NOT ground both ends.

fineshot1 · Post by **fineshot1** » Mon Feb 13, 2006 8:03 am

Cant comment on the Star Sabre light bar as I have little experience with them.

Why would you NOT ground both ends of a strobe cable drain wire?

I have been doing that for years(many many installs) and listen to the mobile units communicate all the time and have never heard any strobe noise on any of my installs. Is the issue a possible ground loop? Please explain...

dbcomm · Post by **dbcomm** » Mon Feb 13, 2006 1:34 pm

fineshot1 wrote:Why would you NOT ground both ends of a strobe cable drain wire?

I have been doing that for years(many many installs) and listen to the mobile units communicate all the time and have never heard any strobe noise on any of my installs. Is the issue a possible ground loop? Please explain...

Short answer: Grounding at both ends creates a loop for current to flow along the shield. This approach is effective against magnetic pickup, however, the possibility for EMI/RF interference is GREATLY increased. So think about it. What is your system more susceptible to; Magnetic or EMI/RF interference? I'd say from my experience that 99% of interference you're going to find eminating from a vehicle is going to be EMI/RF, not magnetic - especially when it comes to strobe PSU's that produce +thousand volt bursts!

fineshot1 · Post by **fineshot1** » Tue Feb 14, 2006 5:39 am

[Grounding at both ends creates a loop for current to flow along the shield. This approach is effective against magnetic pickup, however, the possibility for EMI/RF interference is GREATLY increased.]

I would agree on the likelyhood of EMI being the greater of the worries here but in order for a ground loop to form you must have a difference of potential between the two ground points. In most cases (at least the ones I have delt with) if there is a difference of ground potential it is so very negligable that it can be discounted. This is of course refering to vehicle ground points such as the frame, body parts directly attached to the frame, etc. I have occasionally come across trunk lids, hoods, and some other vehicle parts that have been isolated from ground but I am not refering to that here. Anyway - I have rarely come across a ground loop problem like that you describe above.....dan

Radio noise from Strobes

Radio noise from Strobes

Re: Radio noise from Strobes