CurtPalme.com Home Theater Forum

dvh99 · Joined: 25 Dec 2009 Posts: 2158 Location: nederland

hi i downloaded a new pcb program dip trace that automatically routs the connections and also has the choice to choose between different groundplane patterns.
see an example below, my question is if there is a theory behind this or if this is done just for fun, i know some high end amps (krell mark levinson duson) used such patterns.

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

Have you ever seen the tv show 24? There is a character in the show who has a room with Grids in a cage configuration like the ground plane on the PCB that supposedly blocks all RF emissions so he can be"invisible" to the Government. I bet that pattern is based on the same theory.

Athanasios

dvh99 · Joined: 25 Dec 2009 Posts: 2158 Location: nederland

if that is true i should have known it before, the addon board acts as an antenna(not that bad, but still).
edit: i have never seen 24 btw

Sparky015 · Posted: Wed Dec 08, 2010 1:00 am Post subject:

That phenomina is known as a feriday cage. It works, we used one where we built our pre-amps when I was in the medical industry. What are you trying to do with the board? Board thickness plays a part too if your dealing with signals. Higher the frequency, the less you can get away with.

dvh99 · Joined: 25 Dec 2009 Posts: 2158 Location: nederland

its a simple preamp using the lme49720 (later the 49990 maybe).
the board has a copper layer of 70um.
have to add a phono pre also with the lme49720 and of course a supply 15v + et -
i know the faraday cage btw could have thought of that.
trying to keep the amp under 100 euro.

WanMan · Joined: 19 Mar 2006 Posts: 10270

When I worked in the Low Temperature Physics lab (UF) back in the 90's it was common to have walk-in sized Faraday cages. Even the smallest amounts of EM radiation can cause He3 to boil, which in turn needed to be pumped off (out of the Dewar tank). Mind you we were operating in the milli to micro Kelvin range.

Tom.W · Joined: 09 Mar 2006 Posts: 6635

Another good example of a Faraday cage and what it can shield.

http://www.youtube.com/watch?v=Zi4kXgDBFhw

beun · Joined: 28 Jun 2006 Posts: 676

I don't think that a patterned ground plane has anything to do with a Faraday cage, the ultimate cage is still a solid conductive sheet. The only advantage of fine chicken wire is that it is transparent to light ((also an electro-magnetic wave) meaning there is an upper frequency limit to the RF opaqueness of the cage.

On a PCB the only advantage of the patterned ground plane is that you don't need to use thermal relieve for your via's. For a quality ground plane I would still recommend a solid plane.