<div dir="ltr">Jules,<div><br></div><div>This will have to come to the attention of Scotty. I am now completely excluded from the design process for the magnetometer implementation.<div><br></div><div>Dave</div></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sat, May 30, 2020 at 4:27 PM Julius Madey <<a href="mailto:hillfox@fairpoint.net">hillfox@fairpoint.net</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div>
<font face="Arial">Dave,<br>
I specifically note the change of shield material from copper
alloy to SS. <br>
<br>
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.<br>
<br>
Perhaps Hyomin could provide some guidance on that ?<br>
<br>
Jules<br>
<br>
Delays in 1000 meters of twisted pair cable are, of course, too
long for 100KHz rate i2c exchange protocol, but <br>
</font>
<div>On 5/30/2020 2:21 PM, David Witten
wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">Jules, et. al.:
<div><br>
</div>
<div>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.</div>
<div><br>
</div>
<div>Dave</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sat, May 30, 2020 at 12:59
PM Julius Madey <<a href="mailto:hillfox@fairpoint.net" target="_blank">hillfox@fairpoint.net</a>> wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div> <font face="Arial">Tom,<br>
From a 5/4 email from Scotty explaining the design of his
new board:<br>
</font><font face="Arial"><br>
"JMP6 allows us to ground one side of the shield only to
minimize noise <br>
pickup and ground loops. Note that the CAT5 cable is
shielded. "<br>
<br>
If I interpreted that as a 'recommendation', my bad ...<br>
<br>
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.<br>
<br>
Jules - K2KGJ<br>
<br>
</font><br>
<div>On 5/30/2020 11:45 AM, Tom McDermott wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<div>I have no idea where the idea that the shield
should be unconnected at the remote end came from. <br>
</div>
<div>In my opinion this is contrary to what probably
needs to be done. I think Scotty put a jumper on that</div>
<div>line so it could be tried both ways. Normally one
floats a shield if ground return currents from some</div>
<div>external path are expected. I don't see where
those would come from in this situation.</div>
<div><br>
</div>
<div>-- Tom, N5EG</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sat, May 30, 2020
at 8:31 AM Julius Madey via TangerineSDR <<a href="mailto:tangerinesdr@lists.tapr.org" target="_blank">tangerinesdr@lists.tapr.org</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div> <font face="Arial">Dave,<br>
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. <br>
<br>
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.<br>
<br>
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.<br>
<br>
Jules<br>
</font><br>
<div>On 5/30/2020 10:34 AM, David Witten wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">Jules,
<div><br>
</div>
<div>This is something I had not thought
about. </div>
<div><br>
</div>
<div>It does appear that Belden does sell a
line of Cat 5+ connectors that have little
or no metal in them beyond the contacts:</div>
<div><a href="https://www.belden.com/products/enterprise/copper/connectors/cat-6a-jacks" target="_blank">REVConnect®
Connectivity System</a>, but these appear
to be components of a building wiring
system, not board mountable jacks. Further
research is required.<br>
</div>
<div><br>
</div>
<div>Dave</div>
</div>
</blockquote>
<br>
</div>
-- <br>
TangerineSDR mailing list<br>
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<a href="http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org" rel="noreferrer" target="_blank">http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org</a><br>
</blockquote>
</div>
</div>
</blockquote>
<br>
</div>
</blockquote>
</div>
</blockquote>
<br>
</div>
</blockquote></div>