[TangerineSDR] [EXTERNAL] Re: Getting rid of magnetometer-related RF noise

Bill Engelke bill.engelke at ua.edu
Wed Jun 30 16:42:21 EDT 2021

Alan – with

  *   The magnetometer buried at 2 feet depth
  *   Running shielded CAT6 cable grounded at the R-Pi
I have tested (with the magnetometer running at recommended parameters) on 160 M through 10 M (at 1 KW), on 6M (at 500W) and on 2M (at 50 W) and so far I have not seen any perturbations of the magnetometer from carriers at these bands & power levels.

It has been suggested to me that I try doing some modulation and see if that makes a difference; I still have to run that s of tests.   -73- Bill,  AB4EJ

From: TangerineSDR <tangerinesdr-bounces at lists.tapr.org> On Behalf Of n5pa via TangerineSDR
Sent: Wednesday, June 30, 2021 2:39 PM
To: TAPR TangerineSDR Modular Software Defined Radio <tangerinesdr at lists.tapr.org>
Cc: n5pa <n5pa.dx.341 at gmail.com>; Bill Engelke <bill.engelke at ua.edu>
Subject: [EXTERNAL] Re: [TangerineSDR] Getting rid of magnetometer-related RF noise

Good info to know Bill!  I run QRO on most bands and I am concerned about getting into the magnetometer, also.
Alan Clark, N5PA
Ellisville, MS
Email:  n5pa at n5pa.com<mailto:n5pa at n5pa.com>
URL:  http://www.n5pa.com<https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.n5pa.com%2F&data=04%7C01%7Cbill.engelke%40ua.edu%7C6b803b5bdba9466007b308d93bfee3a9%7C2a00728ef0d040b4a4e8ce433f3fbca7%7C0%7C0%7C637606788214030979%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=IiYe6jSmasEixXVMkrtZN5syd81aSudnMee2jYMfr8g%3D&reserved=0>

On Jun 30, 2021, at 1:25 PM, Bill Engelke via TangerineSDR <tangerinesdr at lists.tapr.org<mailto:tangerinesdr at lists.tapr.org>> wrote:

To all:

You might recall that a few weeks ago I discovered some RF noise appearing on 160 M and 80 M when the magnetometer was hooked up. This was wideband noise on 80M and a birdie on 160M.

Note that I have been using shielded CAT6 cable between the magnetometer base (a Pi-Hat) and the in-ground magnetometer. The noise could be seen clearly in the waterfall on my FlexRadio 6600 connected to my 80M dipole; it was only 1 to 2 s-units, but this might be an issue for DXing.

It required 2 steps to eliminate this noise:

  1.  The ground plane of the R-Pi needs to be connected to an earth ground. This eliminates the birdie on 160M and cuts the 80M noise about in half. Do this by grounding the sleeve of the R-Pi audio jack.
  2.  The remaining 80M noise is due to the Canakit switching power supply that comes in a Raspberry Pi kit. To eliminate that, you must replace the switching power supply with a linear power supply. I found a 4.5 amp linear supply (Pyramid brand, on Amazon $55.79) that has 2 USB jacks (each able to supply 2 amps) plus 13.8 V terminals.*

-73- Bill,  AB4EJ

* There are cheaper linear power supplies, but R-Pi recommends a supply able to provide 3 amps. Linear power supplies able to provide 3 a are not plentiful or cheap. I measured the actual current pulled by a R-Pi 4 B+, and it is around 1 amp. With the Pyramid supply I am powering two R-Pi 4 B+ computers with power to spare, and the switching noise is gone.
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