The test was carried out by the electrical safety authorities of four countries: Elsäkerhetsverket in Sweden, the Bundesnetzagentur in Germany, BAKOM in Switzerland and Agentshap Telecom in the Netherlands. A total of 30 cables from different manufacturers were included in the test, and as many as 27 of these did not meet the requirements. The test showed that nine out of ten HDMI cables do not meet EMC requirements. According to the authorities, the price of the cable does not directly indicate its quality as some of the most expensive cables were the worst.

Source:
EU testasi HDMI-kaapelit: lähes kaikki reputtivat testissä
https://etn.fi/index.php/13-news/12638-eu-testasi-hdmi-kaapelit-laehes-kaikki-reputtivat-testissae

A bad cable installation destroyed my $2,000 TV and maybe almost killed me
I never knew it could go this wrong
https://www.theverge.com/2016/5/18/11705038/cablevision-coax-destroyed-tv-nearly-killed-me

Brent explains some some common ground problem fixes in your home theater installation

HDMI noise issues can be of two flavors, ingress (entering) or egress (exiting). In HDMI we are concerned about both.

HDMI does have built-in safeguards to fight off ingress noise. One way it does this is by using a balance line cable assembly (differential signaling). This is a wonderful way to provide noiseless cable transmissions. HDMI also insisted on a thin-shielded wrap around the ever-so-critical TMDS lanes. This is to prevent high-frequency emissions and ingress from disturbing the signals. At the same time, however, HDMI also insisted on a braided type of shield around the entire assembly.

The only way to prevent ingress and egress noise from HDMI cabling is shielding.

Impulse noise is a form of RF noise that tends to vary in time. This can be a real SOB to fix due to its random timing. The odds of snagging these impulses at the precise time they propagate into the assembly are virtually zero. In HDMI, we really don’t have the luxury of TDMA (Time Division Multiple Access), or OFDMA (Orthogonal Frequency Division Multiple Access). So you have to use brute force: Shield the SOB.

This is why HDMI cables have so much shielding. One day I grabbed one of our DPL member’s cables – with permission, of course – and started digging into the cable to expose the TMDS lanes. It only took 200mv of amplitude and 1μs of time to totally kill the HDMI signal both for video and audio.

The majority of noise issues in the field are related to ingress, with nearly all of them being Cat 5 and 6 – no shield there to speak of. In this case we need the braided shield. The foil that generally comes with shielded Cat 5 and 6 only works in the higher frequencies. All of these problems appear in the low portion of the spectrum.

What causes these issues? To name just a few: SCR (Silicon Control Rectifiers) dimmers; security alarm systems; microcontrollers (I/O); compressors; motors; neon signs; thermostats; touch lamps; AC power distribution systems; ceiling fans and controls; street lighting and electrical transformers.

Combating HDMI Noise

One sure way to reduce the chances of interference is to use conduit (pipe) as the chase you send your cable through. It can’t be plastic; it must be made of some metal and is typically called RMC or (rigid metal conduit). s type of material is usually found in aluminum, coated steel, or even stainless steel. Any cabling that is chased through RMC is pretty much protected from any outside electrical ingress. e pipe should be grounded at least at both end marks.

Speaking of Grounds …
Poor grounding can also be reasons for ingress to overtake the signal and cause intermittent HDMI A/V. When running long lengths of cable there will always be some potential difference along these wires from beginning to the end.

Most of the noise-emitting devices I mentioned previously are AC related, which means you need to stay as far away as possible from AC lines such as Romex.

Cut it Off at the Source
Is there a way to stop these problems at the source if you can’t stop the noise entering the cable? Yes and no. The first thing to do is find the hardware that is causing the noise. You should know the major culprits that cause these problems to begin with.

If intermittent HDMI occurs, you need to include these interference transmissions as part of your troubleshooting list. First, by way of trial and error, eliminate the ones that could be causing the problem. Just turn it off and check it again. By pure elimination you may be able to find the problem. If you need more help, get a cheap AM radio. Tune to mid band and turn the volume up. Since these noises are usually AC related, the radio will pick up low frequencies. If the screen drops out as you hear loud noise or static, you’ve probably found your problem.

Now use it as a field strength meter and locate the hardware that is causing the problem.

There are three methods for removing USB (and HDMI) cable noise. One is to use a cable with a ferrite noise suppressor sleeve (that big round slug at one end. You can also buy a clip-on ferrite noise suppressor). These are sometimes called a ferrite bead.

The second method is to run a wire that’s less resistive than the USB/HDMI cable shielding from the case of the USB audio interface or HDMI-connected audio component to the case of your computer.

The third method is to get a USB noise filter (I’ve never seen one for HDMI, but an HDMI adapter could work), which is actually a USB re-transmitter that splits the shield connection. These cost around $50 and are said to indeed eliminate the noise