[TangerineSDR] Ferrous Metal connectors on Mag boards and SBCs

Julius Madey hillfox at fairpoint.net
Sat May 30 17:26:36 EDT 2020

I specifically note the change of shield material from copper alloy to SS.

I just ordered the AMP jacks and Stewart plugs in the attached data 
sheets.  Jack shield is plated phosphor bronze and plug shield is plated 
copper.  I don't know if other vendors are changing shield material re 
EMI performance (meaningful at GigE speeds but not at 100KHz 
differential i2c) and since magnetic properties of SS can vary greatly 
depending upon specific alloy and cold working, it's probably a good 
idea to stay away from them if at all possible if the RM3100 will be 
mounted in close proximity to the SS part if the hope is to see signals 
well below the microTesla range.

Perhaps Hyomin could provide some guidance on that ?


Delays in 1000 meters of twisted pair cable are, of course, too long for 
100KHz rate i2c exchange protocol, but
On 5/30/2020 2:21 PM, David Witten wrote:
> 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 
> <mailto: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
>>     <mailto: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 <mailto:TangerineSDR at lists.tapr.org>
>>         http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org

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