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Subject:	Re: NTC - [TN] Pewter as RF screening material
From:	Inge <[log in to unmask]>
Reply To:	Inge <[log in to unmask]>
Date:	Wed, 23 Jun 2010 19:26:16 +0200
Content-Type:	text/plain
Parts/Attachments:	text/plain (341 lines)
Quite right, in fact most are grids. You save weight, easier to form etc. 
There may be one exception: extremly wide band circuits.
/Inge


--------------------------------------------------
From: "Eric Kalgren" <[log in to unmask]>
Sent: den 23 June 2010 18:38
To: "'Inge'" <[log in to unmask]>; <[log in to unmask]>
Subject: RE: NTC - [TN] Pewter as RF screening material

> It doesn't even have to be a solid sheet of metal, a grid with openings
> sized for the lowest frequency you want to block will also work.  See
> also: the screen keeping all those microwaves in the oven where they
> belong.
>
> I used to work at a facility called "The Trestle" which was used to test
> EMP effects on aircraft.  The entire test site was completely surrounded
> by a wire grid, designed to keep the EMP inside and not turn the city of
> Albuquerque off when the EMP generators fired.  I never saw any testing
> but found a fun article.
>
> http://www.chucksville.org/trestle.html
>
> Eric Kalgren
> Electrical Engineer
>
> The Ferrite Co. Inc.
> 165 Ledge Street
> Nashua, NH 03060
> Phone 603-881-5234 X 153
> Fax 603-881-5406
> PRIVILEGED AND CONFIDENTIAL COMMUNICATION
> This E-mail is covered by the Electronic Communications Privacy Act, 18
> U. S. C." 2510-2521 and is legally privileged.  The information
> contained herein is confidential and is intended only for the use of the
> individual or entity named above.  If the reader of this message is not
> the intended recipient, you are hereby notified that any dissemination,
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> If you have received this transmission in error, please immediately
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>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
> Sent: Wednesday, June 16, 2010 1:53 PM
> To: [log in to unmask]
> Subject: Re: [TN] Pewter as RF screening material
>
> Sure you can.  Semding you a table with skin depth vs freq and also RF
> resistivity for some common metals used in PWBs.  Notice the
> considerable
> differencies.  RF designers use to forget this.
> Off line.
> /Inge
>
> --------------------------------------------------
> From: "Eric CHRISTISON" <[log in to unmask]>
> Sent: den 14 June 2010 16:43
> To: <[log in to unmask]>
> Subject: Re: [TN] Pewter as RF screening material
>
>> "Speaking RF signals at radar levels,  magnetrons,
>> klystrons,  TWTs and other high power sources,  I would not use
> pewter."
>>
>> You're talking of peak pulse powers in MW here aren't you?
>>
>> Can't you figure out a minimum thickness for any screening material
> based
>> on something like resistivity and loss tangent, it's called skin depth
> or
>> something?
>>
>>
>>
>>
>>
>> On 14/06/2010 15:18, Mike Fenner wrote:
>>> Hmm....
>>>
>>> Some lead free solders are not a million miles from pewter.
>>>
>>> Regards
>>>
>>> Mike
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
>>> Sent: Thursday, June 10, 2010 7:01 AM
>>> To: [log in to unmask]
>>> Subject: Re: [TN] Pewter as RF screening material
>>>
>>> Hi Grant,
>>>
>>> any METAL case will work.  What you create is a Faraday cage, that
> will
>>> eliminate electrostatic and electromagnetic influence. However,  it
> will
>>> NOT
>>>
>>> eliminate static magnetic fields, nor low frequency electromagnetic
>>> waves.
>>> In such a case you'll need ferro materials,  one of the best being so
>>> called mu metal.  But, as your question was about RF, pewter will
> work,
>>> not
>>> as good as ferro materials, but it depends on the pewter wall
> thickness.
>>> In
>>>
>>> many modern electronics, you get acceptable RF shielding by means of
>>> plastic
>>>
>>> boxes with a thin metal coating only. Works for weak RF signals,
> which
>>> are
>>> often the case within commercial products like mobile telephones and
>>> transistor radios.  Speaking RF signals at radar levels,  magnetrons,
>>> klystrons,  TWTs and other high power sources,  I would not use
> pewter.
>>>
>>> Inge
>>>
>>> --------------------------------------------------
>>> From: "Grant Emandien"<[log in to unmask]>
>>> Sent: den 9 June 2010 11:22
>>> To:<[log in to unmask]>
>>> Subject: [TN] Pewter as RF screening material
>>>
>>>
>>>> Hi,
>>>>
>>>> Does anyone used lead-free pewter for RF screening purposes?
>>>>
>>>> Pros&  Cons?
>>>>
>>>> Regards
>>>> Grant
>>>>
>>>>
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>>
>> -- 
>> Eric Christison Msc
>> Mechanical Engineer
>> Consumer&  Micro group
>> Imaging Division
>>
>> STMicroelectronics (R&D) Ltd
>> 33 Pinkhill
>> Edinburgh EH12 7BF
>> United Kingdom
>>
>> Tel: +44 (0)131 336 6165
>> Fax: + 44 (0)131 336 6001
>>
>>
>>
>>
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