Bed liner sheilding?

[semajniwdoog]

I've heard that one can use pickup truck bed liner products for bass cavity sheilding. Is there any truth in that? My guess is that it's probably pretty serious

Thanks!
JjG

 

[Stinsok]

That would be a very expensive way to go. You can buy small quantities of copper tape online or by aluminum tape at the hardware store.

 

[Nighttrain1127]

I don't think Bedliner Is conductive. It would have to be to act as a shield. The shield bleeds all the EMI/RFI it blocks to ground. If it is conductive it would work,But as mentioned above there is inexpensive copper tape and someone makes a paint on shielding I believe it is available Through Stewart McDonald.

 

[Eight_Stringer]

I don't think Bedliner Is conductive. It would have to be to act as a shield. The shield bleeds all the EMI/RFI it blocks to ground. If it is conductive it would work,But as mentioned above there is inexpensive copper tape and someone makes a paint on shielding I believe it is available Through Stewart McDonald.

Nighttrain your correct to indicate that "shielding" as often quoted here is in fact a decoupling of an unwanted signal or Magnetic( a magnetic field will pass straight through a copper or similar coating ), field from a wanted signal. What near all the postings here think is "shielding" is a decoupling of unwanted induced currents into the wanted signal or path. The application of an electrical conductive area is in fact an interposed device to couple the unwanted voltage/current to a low impedence point or return the unwanted signal back to the interference source.

There is no magical property of a conductive surface to "block" an unwanted signal. It is decoupling your talking about.
This decoupling is in fact a coupling of the unwanted AND wanted signal at a common point or area and is the reason why "shielding" does not always work as expected ie the decoupling/coupling will depended on source/sink impedence, actualy couple the unwanted and wanted signal even more than
without. By this i mean, by "shielding" you can make the problem worse, something that does not happen often however the reason for this worse situation is not understood in basic theory hence no solution seems to work to remove the problem.

By the way, i'm a TEM ( look it up ) wave advocate. If your going to shield an electromagnetic wave then you need to address the magnetic wave and the electro wave together.
Back in the days we used mumetal or commercial name conetic.
This is a magnetic shield and possibly a conductive shield at the same time. Sure some of you with sound basics of TEM theory will take me up on the above. Glad to discuss at length to make this cavity "shielding" better understood.

Regards John

 

[JustDavid]

John, I'm not quite catching if you are saying the material under discussion will or won't do the desired job.

Will it?

 

[Eight_Stringer]

John, I'm not quite catching if you are saying the material under discussion will or won't do the desired job.

Will it?

JustDavid, you can use any conductive material for a cavity "shielding" task. Have no knowledge of what a truck bed liner material is, apart from the tough plastics i hear about.

Cavity "shielding" is a two way street. By covering the entire cavity in conductive material you are hoping to couple this unwanted signal to a low impedence point. What it also does is couple all of the interconnect wires to the "shield". Should the impedence or return path be not working effectively then what you have done is increased the coupling of unwanted and wanted signals via the "shield"

My choice in effective wanted and unwanted signals coupling prevention would put cavity shielding as plan Z. Circuit impedence needs addressing as well as PUP ( A Variable Reluctor device or VR ) as to unwanted magnetic field interference, something an electricaly conductive shield would be hard pressed to prevent. If i really wanted to go overboard i could make up a small "box" of mumetal to house the control circuits and wiring, it would assist in the reduction external magnetic field coupling and if lucky the external electrical signals.
Though by its nature a PUP works on disturbed magnetic field as there is a permanent magnet inside the PUPs with a winding of wire around the magnet that produces a voltage when this magnetic field cuts across the windings. Going to all the trouble of magnetic shielding the control circuit would not be easy and only to have a magnetic style input signal would make the effort great for little return.

Hope it is an answer of sorts for you. I'm not trying to be a one stop answer for all the individual cases of noise supression, just the background behind the techniques on offer.

Will try a better reply if not clear...regards John

 

[JustDavid]

Thanks John.

I think the discussion has two parts:
1/ how to shield & with what
2/ will the stuff in question do it.

Item 2 kinda depends on what the stuff in question has in it. If no conductive or ferric materials, it'll do nothing other than protect the inner wood from damage due to dislodged internal parts.

Item 1 in a seperate reply.

 

[JustDavid]

My understanding of how to shield is to:
1/ create an antenna that will pick up noise before it gets picked up in the wrong locations
2/ get rid of that.

For #1, I believe a conductive casing that, as much as possible, surrounds the pickups & electronics chambers will work. The casing can't be complete as we still need the pickups' magnetic field to be affected by the strings.

For #2, we connect the conductive casing to our best available ground/non-signal point; the Sleeve.

Any major stupids so far?