[TangerineSDR] TangerineSDR Digest, Vol 14, Issue 36

Julius Madey hillfox at fairpoint.net
Sat May 30 08:54:51 EDT 2020


Very curious.  My two Pi's and an Asus Tinkerboard have ferrous metal 
housings on the USB A receptacles, non-ferrous on the USB micro power 
connector.  One Pi has ferrous metal on the HDMI connector but the other 
one and the Tinkerboard are non-ferrous HDMI shells.

The RJ45 jacks have a non ferrous housing on all three micros BUT the 
shielded RJ45 plugs I just installed on the extension cable I'm testing 
both have ferrous metal shells. Does anyone have a part number for a 
non-ferrous shielded plug?
Jules-K2KGJ


On 5/29/2020 12:00 PM, tangerinesdr-request at lists.tapr.org wrote:
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> Today's Topics:
>
>     1. Re: TangerineSDR Digest, Vol 14, Issue 35 (David Witten)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 28 May 2020 11:28:56 -0500
> From: David Witten <wittend at wwrinc.com>
> To: tangerinesdr at lists.tapr.org
> Subject: Re: [TangerineSDR] TangerineSDR Digest, Vol 14, Issue 35
> Message-ID:
> 	<CABJ3BVPHeA8XGa9RwvLEhotfDXSf4aDX4mh1g30vDihRoPLO1A at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> NB:
>
> Even the Simple Magnetometer Magnetometer Support Boards (SMSBs) should be
> able to avoid this problem if attached using the Qwiic Cable - 500mm
> <https://www.sparkfun.com/products/14429>, the Qwiic Cable - 200mm
> <https://www.sparkfun.com/products/14428>, or their equivalents from
> AdaFruit.  I believe that I provided one or the other of these with any of
> the boards I sent out for testing.  Care in positioning is left up to the
> user.
>
> The problem probably only applies to upcoming raspberry-pi hats in local
> mode (with the magnetometer sitting on top of the pi).  But in some
> non-professional cases, convenience may outweigh the loss of sensitivity,
> esp functional testing.
> People in the Drone community claim to have used uMetal for shielding to
> good effect (from PM motors, etc) but this does not sound like good
> practice for sensitive instruments.
>
> And anyone using these boards in the remote extender configuration will
> find it difficult to place the far end board that close with any amount of
> shielded Cat-6 in between.
>
> Dave
>
> On Thu, May 28, 2020 at 11:00 AM <tangerinesdr-request at lists.tapr.org>
> wrote:
>
>> Send TangerineSDR mailing list submissions to
>>          tangerinesdr at lists.tapr.org
>>
>> To subscribe or unsubscribe via the World Wide Web, visit
>>          http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org
>> or, via email, send a message with subject or body 'help' to
>>          tangerinesdr-request at lists.tapr.org
>>
>> You can reach the person managing the list at
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>>
>> When replying, please edit your Subject line so it is more specific
>> than "Re: Contents of TangerineSDR digest..."
>> Today's Topics:
>>
>>     1. Raspberry Pi connectors produce magnetic interference
>>        (Phil Erickson)
>>
>>
>>
>> ---------- Forwarded message ----------
>> From: Phil Erickson <phil.erickson at gmail.com>
>> To: TAPR TangerineSDR Modular Software Defined Radio <
>> tangerinesdr at lists.tapr.org>
>> Cc:
>> Bcc:
>> Date: Thu, 28 May 2020 08:45:18 -0400
>> Subject: [TangerineSDR] Raspberry Pi connectors produce magnetic
>> interference
>> Hi all,
>>
>>    For those working on the PSWS magnetometer project, I'd like to pass
>> along some findings made by Nick Belsten (MIT student) on our AERO/VISTA
>> cube satellite team.  As background, AERO/VISTA is a twin cubesat mission
>> with the goal of investigating the radio aurora at 400 kHz to 5 MHz in low
>> Earth orbit, and will fly in 2022 through the NASA Heliophysics small
>> satellite explorer program.  MIT Haystack is the lead with MIT Lincoln
>> Laboratory providing the advanced electromagnetic vector sensor package.
>> Other participants include Dartmouth, Merrimack College, Morehead State
>> University, and MIT AeroAstro.
>>
>>    Each of the two cubesats will have an Auxiliary Sensor Package for
>> coincidence detection of the aurora (other than radio) that includes a
>> magnetometer.  Nick has been in charge of some of the magnetometer
>> package development, and reports that stock Raspberry Pi connectors contain
>> steel that is magnetized and that causes deflections on the order of 2 uT
>> at 3 cm distance.  Given scaling laws, it is therefore recommended to keep
>> the magnetometer at least 8-10 cm away from Raspberry Pi hardware to avoid
>> systematic bias or possible degradation in uncertainty if you are targeting
>> 50 nT type measurement capabilities.
>>
>>    Nick is writing a memo on his findings and procedure so please contact
>> me off-list if you would like to hear from him directly.
>>
>>    Just an caveat / advisory note (perhaps not relevant) if anyone is
>> running a test configuration with magnetometers next to a R-Pi, rather than
>> at the end of a long cable.  Perhaps it's also prudent to examine the
>> magnetic characteristics of connectors on the TangerineSDR?
>>
>> 73
>> Phil W1PJE
>>
>> --
>> ----
>> Phil Erickson
>> phil.erickson at gmail.com
>> TangerineSDR mailing list
>> TangerineSDR at lists.tapr.org
>> http://lists.tapr.org/mailman/listinfo/tangerinesdr_lists.tapr.org
>>
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