[TangerineSDR] TangerineSDR Digest, Vol 14, Issue 35

[David Witten]

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:

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>    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
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