[TangerineSDR] Found a method to reduce magnetometer-related RF noise

[Bill Engelke]

To all:

In my previous posts, I documented that there is noise on 80M and 160M that comes and goes depending on whether the magnetometer is powered on or off. Since the magnetometer's circuits were designed to avoid this, this  caused some consternation.... But I think I found a reason, as well as a partial cure.

I tried putting ferrite core chokes on both ends of the shielded CAT6, which made no difference; but then I asked myself, how do I know if this CAT6 shield is really grounded??

Answer:  IT'S NOT, because the entire Raspberry Pi is not grounded.  Its chassis floats, unless you run a wire between the R-Pi and earth ground.

The R-Pi has a nice 1/8" audio jack, which we don't use for this project.... But the ring is ground.  When I connect the audio jack ring (not the tip!) to ground, the RF noise is greatly reduced (it is gone on 160M, and reduced by about half on 80M), and the birdie on 160M disappears. There is still some noise that seems attributable to the magnetometer on 80M, but I am having trouble characterizing it in detail due to a lot of storm-related atmospheric noise.  So anyway, this may be another piece in the puzzle....    -73 - Bill,  AB4EJ


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