[TangerineSDR] Ferrous Metal connectors on Mag boards and SBCs

[David Witten]

Jules, et. al.:

FWIW:  The Amphenol drawing w/details for the RJ45 that I used on the
prototypes is attached.  It indicates that the shield is tin coated
stainless steel.  Depending on the alloy it may exhibit some degree of
ferromagnetism.

Dave

On Sat, May 30, 2020 at 12:59 PM Julius Madey <hillfox at fairpoint.net> wrote:

> Tom,
> From a 5/4 email from Scotty explaining the design of his new board:
>
> "JMP6 allows us to ground one side of the shield only to minimize noise
> pickup and ground loops. Note that the CAT5 cable is shielded. "
>
> If I interpreted that as a 'recommendation', my bad ...
>
> Molex has at least one RJ shielded plug using brass .... mine were cheap
> eBay stuff ... so there appears to be no problem.....just have to order the
> good stuff....non ferrous metal construction is available on both RJ45
> jacks and plugs.
>
> Jules - K2KGJ
>
>
> On 5/30/2020 11:45 AM, Tom McDermott wrote:
>
> I have no idea where the idea that the shield should be unconnected at the
> remote end came from.
> In my opinion this is contrary to what probably needs to be done.  I think
> Scotty put a jumper on that
> line so it could be tried both ways.   Normally one floats a shield if
> ground return currents from some
> external path are expected.   I don't see where those would come from in
> this situation.
>
> -- Tom, N5EG
>
>
>
>
> On Sat, May 30, 2020 at 8:31 AM Julius Madey via TangerineSDR <
> tangerinesdr at lists.tapr.org> wrote:
>
>> Dave,
>> I hadn't either until I saw the note from Phil.  I've been using your
>> original small adapter board with the Quicc connectors so haven't run into
>> the issue yet.
>>
>> Two shielded RJ45 PC through hole jacks in my parts drawer, made by BERG,
>> have non ferrous shields.  Couldn't find the BERG part on line but DigiKey
>> carries several candidates.  One is AMP 5558342-1, the data sheet for which
>> shows phosphor bronze as the shield material.  Since the shields on the RJ
>> jacks of the three SBC's I have are all non-ferrous, it may be that for
>> RJ45's, non-ferrous construction is the usual.
>>
>> With regard to the shielded RJ plugs on the extension cable, since the
>> current recommendation seems to be to only tie the shield to ground at the
>> 'local' end, it's possible to remove the shield on the plug at the remote
>> end; just did that with one of mine.
>>
>> Jules
>>
>> On 5/30/2020 10:34 AM, David Witten wrote:
>>
>> Jules,
>>
>> This is something I had not thought about.
>>
>> It does appear that Belden does sell a line of Cat 5+ connectors that
>> have little or no metal in them beyond the contacts:
>> REVConnect® Connectivity System
>> <https://www.belden.com/products/enterprise/copper/connectors/cat-6a-jacks>,
>> but these appear to be components of a building wiring system, not board
>> mountable jacks.  Further research is required.
>>
>> Dave
>>
>>
>> --
>> TangerineSDR mailing list
>> TangerineSDR at lists.tapr.org
>> http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org
>>
>
>
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