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Today's Topics:
1. USRP EMI Solution (Mark McCarron)
2. USRP EMI Solution (Hilbert Transform)
3. Re: USRP EMI Solution (Mark McCarron)
4. Re: USRP EMI Solution (Mark McCarron)
5. Re: USRP EMI Solution (Mark McCarron)
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Message: 1
Date: Sat, 18 May 2013 22:09:39 +0100
From: Mark McCarron <[email protected]>
To: "[email protected]" <[email protected]>
Subject: [USRP-users] USRP EMI Solution
Message-ID: <[email protected]>
Content-Type: text/plain; charset="iso-8859-1"
Has anyone considered constructing an EMI shield box for the USRP?
Regards,
Mark McCarron
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Message: 2
Date: Sat, 18 May 2013 17:42:09 -0400
From: Hilbert Transform <[email protected]>
To: [email protected]
Subject: [USRP-users] USRP EMI Solution
Message-ID:
<CANh_XYc-_j6-xP9faw=k1niHvHoBjTH3vs7=0jnwnorbltw...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Mark writes:
>Has anyone considered constructing an EMI shield box for the USRP?
>
>Regards,
>
>Mark McCarron
You mean, other than the one that comes with it? The box is metallic,
grounded, and most of the perforations in it are a tiny fraction of a
wavelength up to a few GHz. If I were
operating in high RF fields above about 3GHz, I might replace the fan
grille with
some steel mesh.
The USB cable Ettus supplies includes a common-mode choke, as does the
power cable.
For lower frequencies (below 50Mhz) adding more common-mode chokes to those
cables will likely help, and they're available on eBay reasonably cheaply.
But, as far as I know, the existing steel cabinet was engineered to provide
EMI isolation, and given its material and construction, it can't help but
do so, due to physics...
--
Hilbert (Godamn) Transform
[email protected]
Purveyor of fine Hilbert (Godamn) Transforms since 2013
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Message: 3
Date: Sat, 18 May 2013 22:58:53 +0100
From: Mark McCarron <[email protected]>
To: "[email protected]" <[email protected]>
Subject: Re: [USRP-users] USRP EMI Solution
Message-ID: <[email protected]>
Content-Type: text/plain; charset="iso-8859-1"
That's not an EMI shield. The metal is painted and would be effectively
transparent to EMI/RFI. What is required is a continuously conducting surface
with proper sealed inputs and EMI gaskets.
Its incredibly hard to properly seal anything from EMI/RFI.
Regards,
Mark McCarron
Date: Sat, 18 May 2013 17:42:09 -0400
From: [email protected]
To: [email protected]
Subject: [USRP-users] USRP EMI Solution
Mark writes:
>Has anyone considered constructing an EMI shield box for the USRP?
>
>Regards,
>
>Mark McCarron
You mean, other than the one that comes with it? The box is metallic,
grounded, and most of the perforations in it are a tiny fraction of a
wavelength up to a few GHz. If I were
operating in high RF fields above about 3GHz, I might replace the fan grille
with
some steel mesh.
The USB cable Ettus supplies includes a common-mode choke, as does the power
cable.
For lower frequencies (below 50Mhz) adding more common-mode chokes to those
cables will likely help, and they're available on eBay reasonably cheaply.
But, as far as I know, the existing steel cabinet was engineered to provide EMI
isolation, and given its material and construction, it can't help but do so,
due to physics...
--
Hilbert (Godamn) Transform
[email protected]
Purveyor of fine Hilbert (Godamn) Transforms since 2013
_______________________________________________
USRP-users mailing list
[email protected]
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
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Message: 4
Date: Sat, 18 May 2013 23:38:06 +0100
From: Mark McCarron <[email protected]>
To: "[email protected]" <[email protected]>
Subject: Re: [USRP-users] USRP EMI Solution
Message-ID: <[email protected]>
Content-Type: text/plain; charset="iso-8859-1"
Hilbert,
I've designed EMI/RFI solutions and TEMPEST secure rooms to protect computing,
comms and humans. That box may as well be tissue paper.
Grounded means nothing other than general electrical safety (even then there
are caveats to this). An EMI/RFI shield extends a ground reference around an
object. That's not as easy as it sounds.
Regards,
Mark McCarron
Date: Sat, 18 May 2013 18:24:30 -0400
Subject: Re: [USRP-users] USRP EMI Solution
From: [email protected]
To: [email protected]
The metal is *grounded*. It doesn't matter whether it's painted, or not. The
paint issue is along the seams in
any type of cabinet. Ideally, you want all the seams to be one continuous
ground, and if you have a cabinet
that fits-together mechanically, that's where you'll typically find RF gasket
material between two non-painted
surfaces. But the paint, in and of itself, is irrelevant.
Certainly, if you're going to be operating any kind of RF device like this in a
*very high* EMI environment, you might
want to build yourself a faraday cage with welded seams, and improved RF
choking on all non-RF
ingress/egress points.
The existing cabinetry is more than adequate for most applications. Hardly
"transparent".
For RX, you only have to get the "RF leakage through the cabinet" to
significantly below "RF I would have received
from the antenna in the same EM field".
And the secondary emissions from the device itself are required to pass
various tests, as far as I know,
like FCC and CE testing. Again, in order to pass those tests, the cabinet
can't possibly be "transparent".
That's just absurd.
On Sat, May 18, 2013 at 5:58 PM, Mark McCarron <[email protected]> wrote:
That's not an EMI shield. The metal is painted and would be effectively
transparent to EMI/RFI. What is required is a continuously conducting surface
with proper sealed inputs and EMI gaskets.
Its incredibly hard to properly seal anything from EMI/RFI.
Regards,
Mark McCarron
Date: Sat, 18 May 2013 17:42:09 -0400
From: [email protected]
To: [email protected]
Subject: [USRP-users] USRP EMI Solution
Mark writes:
>Has anyone considered constructing an EMI shield box for the USRP?
>
>Regards,
>
>Mark McCarron
You mean, other than the one that comes with it? The box is metallic,
grounded, and most of the perforations in it are a tiny fraction of a
wavelength up to a few GHz. If I were
operating in high RF fields above about 3GHz, I might replace the fan grille
with
some steel mesh.
The USB cable Ettus supplies includes a common-mode choke, as does the power
cable.
For lower frequencies (below 50Mhz) adding more common-mode chokes to those
cables will likely help, and they're available on eBay reasonably cheaply.
But, as far as I know, the existing steel cabinet was engineered to provide EMI
isolation, and given its material and construction, it can't help but do so,
due to physics...
--
Hilbert (Godamn) Transform
[email protected]
Purveyor of fine Hilbert (Godamn) Transforms since 2013
_______________________________________________
USRP-users mailing list
[email protected]
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
_______________________________________________
USRP-users mailing list
[email protected]
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
--
Hilbert (Godamn) Transform
[email protected]
Purveyor of fine Hilbert (Godamn) Transforms since 2013
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Message: 5
Date: Sun, 19 May 2013 01:11:45 +0100
From: Mark McCarron <[email protected]>
To: "[email protected]" <[email protected]>
Subject: Re: [USRP-users] USRP EMI Solution
Message-ID: <[email protected]>
Content-Type: text/plain; charset="iso-8859-1"
The requirements are different, but how much EMI/RFI shielding do you think the
box provides?
I can tell you now it would be around 1dB, if even that. It really is as
effective as tissue paper. It may couple some near-field effects but not much.
Regards,
Mark McCarron
Date: Sat, 18 May 2013 19:24:04 -0400
Subject: Re: [USRP-users] USRP EMI Solution
From: [email protected]
To: [email protected]
The requirements of TEMPEST and the requirements of ordinary commercial EMC are
very, very different.
Because a box doesn't meet TEMPEST says essentially *zero* about its
suitability for ordinary commercial
applications in the EMC realm.
I've been inside the photon-locked shielded room at NRAO, and other similar
rooms. Ordinary commercial gear
*does not* need to meet those requirements. At all. Ever.
Open up a standard commercial-grade or ham-radio grade receiver/transceiver
sometime. You'll find that there's
no extensive RF gasketting (if any at all). Just a metal box that is bonded,
in several places to the system
ground, and the RF connector grounds are common with the cabinet. They
aren't "tissue paper", but they aren't
TEMPEST-qualified either.
I've been involved in radio since 1986. Installed a crap-ton of RF equipment,
done system designs, etc, etc.
For ordinary commercial and amateur-radio applications. NONE of it was
TEMPEST-qualified, because, well,
for ordinary commercial purposes, it didn't need to be.
On Sat, May 18, 2013 at 6:38 PM, Mark McCarron <[email protected]> wrote:
Hilbert,
I've designed EMI/RFI solutions and TEMPEST secure rooms to protect computing,
comms and humans. That box may as well be tissue paper.
Grounded means nothing other than general electrical safety (even then there
are caveats to this). An EMI/RFI shield extends a ground reference around an
object. That's not as easy as it sounds.
Regards,
Mark McCarron
Date: Sat, 18 May 2013 18:24:30 -0400
Subject: Re: [USRP-users] USRP EMI Solution
From: [email protected]
To: [email protected]
The metal is *grounded*. It doesn't matter whether it's painted, or not. The
paint issue is along the seams in
any type of cabinet. Ideally, you want all the seams to be one continuous
ground, and if you have a cabinet
that fits-together mechanically, that's where you'll typically find RF gasket
material between two non-painted
surfaces. But the paint, in and of itself, is irrelevant.
Certainly, if you're going to be operating any kind of RF device like this in a
*very high* EMI environment, you might
want to build yourself a faraday cage with welded seams, and improved RF
choking on all non-RF
ingress/egress points.
The existing cabinetry is more than adequate for most applications. Hardly
"transparent".
For RX, you only have to get the "RF leakage through the cabinet" to
significantly below "RF I would have received
from the antenna in the same EM field".
And the secondary emissions from the device itself are required to pass
various tests, as far as I know,
like FCC and CE testing. Again, in order to pass those tests, the cabinet
can't possibly be "transparent".
That's just absurd.
On Sat, May 18, 2013 at 5:58 PM, Mark McCarron <[email protected]> wrote:
That's not an EMI shield. The metal is painted and would be effectively
transparent to EMI/RFI. What is required is a continuously conducting surface
with proper sealed inputs and EMI gaskets.
Its incredibly hard to properly seal anything from EMI/RFI.
Regards,
Mark McCarron
Date: Sat, 18 May 2013 17:42:09 -0400
From: [email protected]
To: [email protected]
Subject: [USRP-users] USRP EMI Solution
Mark writes:
>Has anyone considered constructing an EMI shield box for the USRP?
>
>Regards,
>
>Mark McCarron
You mean, other than the one that comes with it? The box is metallic,
grounded, and most of the perforations in it are a tiny fraction of a
wavelength up to a few GHz. If I were
operating in high RF fields above about 3GHz, I might replace the fan grille
with
some steel mesh.
The USB cable Ettus supplies includes a common-mode choke, as does the power
cable.
For lower frequencies (below 50Mhz) adding more common-mode chokes to those
cables will likely help, and they're available on eBay reasonably cheaply.
But, as far as I know, the existing steel cabinet was engineered to provide EMI
isolation, and given its material and construction, it can't help but do so,
due to physics...
--
Hilbert (Godamn) Transform
[email protected]
Purveyor of fine Hilbert (Godamn) Transforms since 2013
_______________________________________________
USRP-users mailing list
[email protected]
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
_______________________________________________
USRP-users mailing list
[email protected]
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
--
Hilbert (Godamn) Transform
[email protected]
Purveyor of fine Hilbert (Godamn) Transforms since 2013
_______________________________________________
USRP-users mailing list
[email protected]
http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
--
Hilbert (Godamn) Transform
[email protected]
Purveyor of fine Hilbert (Godamn) Transforms since 2013
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