
The effect of cryptocurrency mining on LTE spectrum - iminehard
https://github.com/iminehard/gpunoise/wiki
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Animats
If you just ground the device ground to a solid earth ground, RF emissions
will usually go way down. The mounting stake and screw of a PC-slot card is
its grounding point. He's bolting those things to painted metal that's bolted
to other painted metal. Just sand the painted metal down a bit at the screw
points before you attach, tie the frame pieces together electrically, and
connect to a power plug ground. Check for ground continuity with an ohmmeter.

~~~
oasisbob
It would take some serious "skill" to plug in a PCI device and not have it
grounded. There are at least a half dozen ground pins in the interface itself.
I don't see what tying the GPU to ground again is meant to accomplish - it's
not adding any shielding to the system as a whole.

DC continuity is not a good measure of impedance as you move into higher
frequency RF signals. Wires that look like low-impedance connections can
easily become accidental antennas.

~~~
dogma1138
It’s not since for PC there is ground to earth through the case since the
(power) ground through the power supply is often interrupted and does not lead
to true earth.

~~~
yjftsjthsd-h
Why? The power supply is a metal box in contact with the metal case; it is
really not connected internally?

~~~
oneweekwonder
As parent said "painted metal". In this video showing how pc cases is made[0].

They mention they automate the powder coating of paint. So the external case
should be well insulated.

[0]:
[https://www.youtube.com/watch?v=XX2i-QhPCD0](https://www.youtube.com/watch?v=XX2i-QhPCD0)

~~~
Animats
_As parent said "painted metal"._

Look at the pictures in the original article. He built his open racks from
multiple painted metal parts. The metal parts probably don't provide a solid
path to ground. Connecting the ground stake to a big piece of metal that's not
grounded adds an antenna to the thing and makes emissions worse.

Easy to fix. Use a Dremel tool and grind off the paint where the stake is
screwed into the metal rail. Use jumper wires (properly, green ones) and
crimped screw lugs to connect the rails together. Connect those to something
that has a grounded case. Check with an ohmmeter to see that there's
continuity between the metal cooling plate on the GPU and the ground pin of
what plugs into the wall. Should be less than 1 ohm. Use an outlet tester to
make sure your wall outlet has a valid ground pin. Now most of your RF hash
gets clamped by the tie to ground.

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superkuh
My interests in cryptocurrency and my interests in radio astronomy started at
about the same time, ~2010. I've definitely been able to notice that broadband
low VHF noise when mining at home. By now I have literal years of recordings
of it. For me it's worst around 144 MHz with my series of AMD GPU (5770, 7870,
7950) using DVI.

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fra
I wonder: isn’t this just the kind of things electronics get FCC tested for?
How did nvidia get accredited by an FCC certified lab given the strong
emissions in those bands?

~~~
blattimwind
Graphics cards only have to comply to EMI standards while mounted inside a
computer chassis.

Ultimately the person/company putting a computer together (or importing it) is
responsible for the whole computer adhering to EMI standards.

~~~
exikyut
Heh, I just pictured a GPU inside an empty PC case, and then immediately
realized of course that wouldn't work, and am now wondering, how do you
generate the necessary load to correctly EMI-test a GPU?

Do GPUs include a secret "crank everything to 11" test mode feature that
exercises all the cores and RAM and everything, so you can just bolt it into a
case, maybe connect it to a fake motherboard that supplies 3.3V or whatever so
the card initializes properly... or do vendors test with a massive pile of
motherboards, measuring and offsetting for the EMI generated by each
motherboard?

~~~
SAI_Peregrinus
If the GPU + Motherboard passes EMI compliance, then the GPU - Motherboard
must also pass, since the motherboard doesn't provide shielding but only adds
noise. So I don't think the particular motherboard should matter. The measured
interference will always be >= to the real interference produced by the GPU
under test.

~~~
exikyut
Hmm, good point, didn't quite look at it that way.

But now I'm wondering if there are motherboards out there that radiate a
little bit more than they should, and force peripheral vendors to do extra
work clipping EMI in their own products.

This is probably not true, since all PCI card vendors would have to test their
products with tons of different boards.

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universenz
This seems like the sort of tool you could use to find large mining rigs that
have been set up in suburbs.

~~~
dogma1138
Thermal imaging is likely going to be better worse case you find a growhouse.

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maxander
This sort of RF signature could allow an "ecowarrior" to go around finding and
sabotaging mining outfits. (Or, y'know, for a boring old burglar to go around
stealing GPUs.)

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tatersolid
Why not enclose your “open” racks with some cheap aluminum screening from the
hardware store?

Attach with Velcro. Also keeps out debris and literal bugs as a side benefit.

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yuhong
It probably does not help that the use of the lower ranges for LTE is
relatively new.

~~~
Scoundreller
Which also penetrates through concrete and drywall better...

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chx
Eventually these cryptoclowns will hit a frequency the FCC will rue and then
we will finally have some much needed respite of this hype as they are shut
down, hard.

~~~
HarryHirsch
The article cited says the FCC has already started:
[https://arstechnica.com/information-
technology/2018/02/bitco...](https://arstechnica.com/information-
technology/2018/02/bitcoin-miner-in-nyc-home-interfered-with-t-mobile-network-
fcc-says/)

The crackdown can't happen soon enough!

