[TangerineSDR] Getting rid of magnetometer-related RF noise

[n5pa]

Good info to know Bill!  I run QRO on most bands and I am concerned about getting into the magnetometer, also.

73,
Alan Clark, N5PA
Ellisville, MS
Email:  n5pa at n5pa.com
URL:  http://www.n5pa.com

> On Jun 30, 2021, at 1:25 PM, Bill Engelke via TangerineSDR <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:
>  
> 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.
> 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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