Metal RF shielding for plastic cases

[KT4HX]

Found this on Ebay. Some guy selling adhesive backed metal shielding. One use of course would be to line the plastic cases used by some scanner manufacturers. Anyone use anything like this? If so, does it help cut down on pc, ignition or other noise? Where would a good source (other than that auction be)? I tried doing a search but didn't really find what he is showing. I know some people use aluminum foil as well. Thanks!

http://cgi.ebay.com/ws/eBayISAPI.dl...;item=5773693390&rd=1&ssPageName=WDVW

 

[SAR923]

I'm not convinced this would really do much good since you'd have to shield the entire case, not just the back. Shielding the entire inside of a plastic scanner case could be a real chore, assuming you could do so in such a way as to not cause a short in a circuit board. Even if this works, you can pick up adhesive backed flexible aluminum tape at almost any home improvment store and not have to buy the stuff off e-bay.

 

[KT4HX]

Yes, the aluminum tape was on alternative I had thought of as well. I agree that the illustration he used of just lining the top the case is of little value. I would think that one would have to line the entire case to achieve any decent results. While I had no intention of buying the stuff he was selling, it did make me wonder as to whether the time and effort would be worth the results.

 

[John_M]

I do not think lining the inside of a scanner with aluminum foil would do much of any good unless your scanner is very close to a Power Supply, the transformer in the power supply could radiate 60Hertz and cause problems with scanner funtioning. Try plugging the power supply of the scanner into another 110ac outlet. I think most interference comes from
strong signals from the antenna in which case shielding the inside of the scanner would do nothing.

 

[N_Jay]

Found this on Ebay. Some guy selling adhesive backed metal shielding. One use of course would be to line the plastic cases used by some scanner manufacturers. Anyone use anything like this? If so, does it help cut down on pc, ignition or other noise? Where would a good source (other than that auction be)? I tried doing a search but didn't really find what he is showing. I know some people use aluminum foil as well. Thanks!

http://cgi.ebay.com/ws/eBayISAPI.dl...;item=5773693390&rd=1&ssPageName=WDVW

You have to figure out what noise you are trying to sheild from, and how it is getting into the scanner BEFORE tring to eliminate it!

 

[KT4HX]

Personally, I'm not trying to eliminate any noise. I was only wondering if shielding would be of any use against things such pc hash, or just other garbage that gets generated inside the home. Obviously anything brought in through the antenna is another issue altogether. I have seen comments to the effect that it was more advantageous to have metal cases (like Uniden) rather than plastic (like RS). I presumed that was primarily because of the shielding effect of the metal case. This was just brought up primarily to see if anyone has tried it and if it did help any.

 

[John_M]

The metal cases would provide added protection. Whether it is necessary I'm not so sure.

 

[N_Jay]

. . I'm not trying to eliminate any noise.
. . .
I was only wondering if shielding would be of any use against things such pc hash, or just other garbage that gets generated inside the home.

That is where I was going.

If the PC hash is gettinginto the receiver through the internal circuits, then sheilding could help.

If the has is getting in through the power or speaker connections, then you need bypassing.

If it is getting in through the antenna, then you need to determine if it is in band or out of band. If out of band it can be filtered, if in band you are most likely SOL. Go back and sheild, filter and bypass the SOURCE!

 

[h8tdigitalradio]

Hello,

There are some polymers that are UV resistant, offer EMI/RFI protection, and can be Static Dissipative, or Conductive. These polymers are used mostly in the Automotive industry or PC Manufacturers. The material is too expensive for consumer electronics. Sheet metal is still cheaper than plastics for shielding applications.

73

Dave AKA The Tripzter :shock:

 

[poltergeisty]

Check these three links out. There about shielding a DX-394 shortwave receiver, which I do own BTW.

Click me

Click me

Click me

So it helps. :wink:

They use shielding made of metal for some military hardware. Why not scanners? :lol:

It's for -EMPS- ( Electro magnetic pulse) an affect of a nuclear blast.

Yes it depends on what type of interference you trying to avoid.

 

[Al42]

I do not think lining the inside of a scanner with aluminum foil would do much of any good unless your scanner is very close to a Power Supply, the transformer in the power supply would radiate 60Hertz and make the scanner inoperable.

My Pro-95 is lying on a 12 volt/2 amp transformer-powered wall wart that's plugged into an outlet strip on my desk. (I'm using the wall wart to keep the scanner at a convenient angle.) It works just fine. The sensitivity of a scanner to radiated 60 Hz is about the same as the sensitivity of your eyes to radiated 450 MHz - none at all. Maybe if you sat the scanner on an unshielded pole pig the speaker might pick up some hum, but 1) normal 60 Hz, even from a nearby transformer, won't affect the scanner and 2) the only way to shield a scanner from 60 Hz is to put the scanner into a screen room.

Back to the original question:

Silver paint, of the kind used to repair PC boards, painted on the inside of the case, makes fair shielding. CB walkie-talkies made way back when used that form of shielding. Is it great? No. Will it cut down on ignition noise? No. Will it cut down noise coming from a PC? Maybe, depending on exactly what the noise is. Would I bother to take my scanner apart to paint it in order to cut down on interference? No, as N-Jay said, I'd find out what was causing the interference and eliminate it at the source, assuming I wasn't just listening for fun. Most (if not all) interference you hear on a scanner gets in via the antenna, and eliminating radiated interference isn't a trivial or cheap task.

 

[John_M]

Get the circuity of the scanner close to a power supply and see what happens. It doesn't matter whether the circuity in the scanner is sensitive to 60HZ or not the EMI created from the power supply will screw up the functioning of the circuitry of the scanner. Obviously the distance between the circuitry and the walls of the scanner on the Pro-95 is sufficient enough to protect the scanner circuitry from 60hz radiation from the power supply.

 

[gr8amp]

Get the circuity of the scanner close to a power supply and see what happens. It doesn't matter whether the circuity in the scanner is sensitive to 60HZ or not the EMI created from the power supply will screw up the functioning of the circuitry of the scanner. Obviously the distance between the circuitry and the walls of the scanner on the Pro-95 is sufficient enough to protect the scanner circuitry from 60hz radiation from the power supply.

I'm not convinced. But, just for fun, I followed your directions, and put my receiver INSIDE my power supply. Everything works fine :roll:

 

[N_Jay]

Get the circuity of the scanner close to a power supply and see what happens. It doesn't matter whether the circuity in the scanner is sensitive to 60HZ or not the EMI created from the power supply will screw up the functioning of the circuitry of the scanner. Obviously the distance between the circuitry and the walls of the scanner on the Pro-95 is sufficient enough to protect the scanner circuitry from 60hz radiation from the power supply.

I'm not convinced. But, just for fun, I followed your directions, and put my receiver INSIDE my power supply. Everything works fine :roll:

Some people just don't know everything they KNOW!

 

[John_M]

Guys general rule of thumb, keep power supplys away from circuit boads. Like I said before, the distance between the circuitry of the scanner and the wall of the scanner seems to be sufficient to protect the circuitry from the power supply. Try taking the back off of the scannner
and put the power supply close to the circuitry. I used to have to glue a peice of sheet metal onto the top of a power supply so to stop the radiation from effecting circuit boards that were close to the power supply.
Without the piece of sheet metal the circuit boards simply would not function.

 

[John_M]

Get the circuity of the scanner close to a power supply and see what happens. It doesn't matter whether the circuity in the scanner is sensitive to 60HZ or not the EMI created from the power supply will screw up the functioning of the circuitry of the scanner. Obviously the distance between the circuitry and the walls of the scanner on the Pro-95 is sufficient enough to protect the scanner circuitry from 60hz radiation from the power supply.

I'm not convinced. But, just for fun, I followed your directions, and put my receiver INSIDE my power supply. Everything works fine :roll:

Some people just don't know everything they KNOW!

What is that supposed to mean?

 

[John_M]

Get the circuity of the scanner close to a power supply and see what happens. It doesn't matter whether the circuity in the scanner is sensitive to 60HZ or not the EMI created from the power supply will screw up the functioning of the circuitry of the scanner. Obviously the distance between the circuitry and the walls of the scanner on the Pro-95 is sufficient enough to protect the scanner circuitry from 60hz radiation from the power supply.

I'm not convinced. But, just for fun, I followed your directions, and put my receiver INSIDE my power supply. Everything works fine :roll:

That power supply is all incased in steel which stops the radiation.

 

[N_Jay]

Get the circuity of the scanner close to a power supply and see what happens. It doesn't matter whether the circuity in the scanner is sensitive to 60HZ or not the EMI created from the power supply will screw up the functioning of the circuitry of the scanner. Obviously the distance between the circuitry and the walls of the scanner on the Pro-95 is sufficient enough to protect the scanner circuitry from 60hz radiation from the power supply.

I'm not convinced. But, just for fun, I followed your directions, and put my receiver INSIDE my power supply. Everything works fine :roll:

That power supply is all incased in steel which stops the radiation.

Interference and interference susceptibility is a mater of degrees.

When you start thinking in terms of 'definites' you are missing the big picture.

 

[John_M]

No comment.

 

[John_M]

N,Jay I couldn't open up your private message for some reason
this site is slow right now. What did you ask?