GPS shielding should be grounded?

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Badzilla

Badzilla

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Anybody else wonder about the GPS shielding just sitting there without being grounded? Electronics is not like ordinary defensive mechanisms. When you stick a material between two places, to shield against electrical interference, AFAIK the material should be grounded.

I see 3DR is trying to sell a "GPS Shield V2". Still appears to be ungrounded. The advertising says "an emir absorbing Polymer shield". I suppose they meant "EMI" but they still appear to be making the same mistake of thinking that a physical property of absorbing something will be effective in protecting against electrical interference. Even if physical absorption were a good analogy, eventually the absorbed interference must go elsewhere.

Patent US6652777 - Method and apparatus for EMI shielding
Method and apparatus for EMI shielding
"Failure to ground the gasket adequately could result in radiation of an electromagnetic field from a side of the gasket opposite the primary EMI field."

Disclaimer: I am not knocking the Solo, I just ordered one.
 
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No it does not and should not be grounded. That just creates a whole new path for RFI to travel and radiate from from/through. What your saying has merit, just not here.
 
Badzilla said:
Anybody else wonder about the GPS shielding just sitting there without being grounded? Electronics is not like ordinary defensive mechanisms. When you stick a material between two places, to shield against electrical interference, AFAIK the material should be grounded.

I see 3DR is trying to sell a "GPS Shield V2". Still appears to be ungrounded. The advertising says "an emir absorbing Polymer shield". I suppose they meant "EMI" but they still appear to be making the same mistake of thinking that a physical property of absorbing something will be effective in protecting against electrical interference. Even if physical absorption were a good analogy, eventually the absorbed interference must go elsewhere.

Patent US6652777 - Method and apparatus for EMI shielding
Method and apparatus for EMI shielding
"Failure to ground the gasket adequately could result in radiation of an electromagnetic field from a side of the gasket opposite the primary EMI field."

Disclaimer: I am not knocking the Solo, I just ordered one.
Click to expand...
If it is made from the 3M material, then what it actually does is convert the EM Radiation to thermal radiation. In that sense it is a true absorber (and re-radiator, but *way* down the spectrum)
 
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Put 50 cents of copper tape shielding on a Solo (grounded or not). Fly for days and mark down your SAT count. Then add $15 of that 3M mat. You will not gain a single satellite or any other benefit I can measure.
 
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skyhax said:
Put 50 cents of copper tape shielding on a Solo (grounded or not). Fly for days and mark down your SAT count. Then add $15 of that 3M mat. You will not gain a single satellite or any other benefit I can measure.
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This is the opposite of what most people experience, myself included.
 
All extra shielding performs so poorly on every Solo I have I wonder if most noise is getting through the GPS cable. I wish I could get/make a high end GPS cable.
 
skyhax said:
All extra shielding performs so poorly on every Solo I have I wonder if most noise is getting through the GPS cable. I wish I could get/make a high end GPS cable.
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It isn't. It is RFI coming from below and into the GPS antenna. The copper foil does very little. The cardboard thing is only going to do something if there is a contact issue, which happens very infrequently, so it usually does nothing. The new v2 absorption shield works wonders.
 
miranda said:
Absolutely. Grounding is essential not optional. Without grounding, shielding has no meaning.
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Same way that wifi signals aren't blocked by a wall of lead unless it's grounded, and visible light (which is just another frequency of electromagnetic radiation) isn't blocked by a sheet of aluminum foil unless it's grounded. Right? :D (Sorry, I couldn't resist. Does that make me a superconductor?)
 
miranda said:
Absolutely. Grounding is essential not optional. Without grounding, shielding has no meaning.
Click to expand...

In most cases that is true, but we're not installing a shield here. We are installing an absorber. It's a more effective approach at the frequencies involved here. The circuit board design and ground plane comes into play also.
 
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Joe Horn said:
Same way that wifi signals aren't blocked by a wall of lead unless it's grounded, and visible light (which is just another frequency of electromagnetic radiation) isn't blocked by a sheet of aluminum foil unless it's grounded. Right? :D (Sorry, I couldn't resist. Does that make me a superconductor?)
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Sounds like a troll. There are plenty of situations in which grounding is necessary. Cable shielding is the most obvious common example of grounded shielding.
 
KDan said:
In most cases that is true, but we're not installing a shield here. We are installing an absorber. It's a more effective approach at the frequencies involved here. The circuit board design and ground plane comes into play also.
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Apparently what it does is change the frequency of the received signal. So that the emitted signal is at a different (much lower) frequency that does not affect the GPS components. Perhaps analogous to shooting bullets through something. The bullets come out the other side, but much slower.
 
Badzilla said:
Apparently what it does is change the frequency of the received signal. So that the emitted signal is at a different (much lower) frequency that does not affect the GPS components. Perhaps analogous to shooting bullets through something. The bullets come out the other side, but much slower.
Click to expand...

That example is perhaps somewhat correct, except that speed is not altered. Part of the energy is absorbed and converted to heat. Certain materials are good at absorbing certain frequencies of EM radiation. Think microwave oven for example.
 
As a test, I grounded a copper shield I had installed, better quality and thicker copper, made no difference to the gps performance. Placing the shield on a spacer of at least 8mm gap made a difference and again grounding made no difference.

The frequency range of the 3M or other shield/absorber covers quite a bit. 3DR's V2 shield performs better than all the previous mods.
 
I was under the impression the copper shield was more of a reflector. Isolating the gps signal and reflecting it back to the main board for minimal interference with other systems and maximum performance. Since the antenna is in the leg, I don't know...
 
KDan said:
That example is perhaps somewhat correct, except that speed is not altered.
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A higher frequency oscillates faster than a lower frequency. Of course the analogy is far from perfect, but it is easy to understand. When a sponge is full of water, it cannot absorb any more water. So that one is difficult to apply.
 
J0S0L0 said:
I was under the impression the copper shield was more of a reflector. Isolating the gps signal and reflecting it back to the main board for minimal interference with other systems and maximum performance. Since the antenna is in the leg, I don't know...
Click to expand...
Isn't the antenna in the leg for the WiFi card and not related to the GPS?
 
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