soldering HDMI over ethernet

[cyberctrl]

I am doing an experimental project passing HDMI signal over ethernet cable using two of these:
https://www.amazon.com/MOTONG-Netwo...479869101&sr=8-15&keywords=hdmi+over+ethernet

When I cut and solder one of the 8 wires of one of the two ethernet cables that is in the middle I get no signal anymore. Can someone please explain why this is happening?

 

[FvM]

When I cut and solder one of the 8 wires

What does "cut and solder exactly mean"? The ethernet cable is made of shielded twisted pairs, differential transmission lines with defined characteristic impedance. For HDMI speed, the pairs must not be untwisted or unshielded for more than one or two centimeter length. Also the length of all twisted pairs must be matched in a 10 cm range.

 

[cyberctrl]

Hi! thanks for the impressive answer, you also answered a couple of other questions that I had.

What does "cut and solder exactly mean"? It means I cut with pliers and I re-solder but it doesn't work.

But now I found out why: when I untwist a pair of cables on the ethernet it does not work even without cutting.

Do you see a chance overcoming this problem? I want to cut and "bridge" the ethernet cable or just HDMI or even VGA with rods of copper for my project.

What If I use HDMI-VGA adapter, then the cables are not twisted. Do you see the chance that I could cut the VGA cable and bridge with copper then feed HDMI again?

I also tried just cutting HDMI cable and then soldering but it does not work. Any explanation?

Many thanks.

Basically I am trying to bridge my HDMI cable with copper rods (cut all 19 HDMI wires and insert 19 copper rods) and this is why I tried with HDMI-ethernet adapter. Could you please advise if this is possible at all and what is the most plausible way to do it? Using any kind of adapter, repeater, amplifier? many thanks

 

[FvM]

What's the purpose of these "copper rods"? HDMI signal pairs are differential transmission lines, you need to keep the characteristic impedance along the way. The auxiliary signals (DDC etc.) are not so critical.

HDMI switch and "retimer" ICs are available from major manufacturers like TI.

 

[cyberctrl]

Many thanks for the response!

This is an artistic/experimental project, the copper rods will form a sculpture. I am feeding via HDMI a VR Headset to be more specific.

Do you think the way to go is to use HDMI and keep all parameters (length) etc as precise as possible?

Would it make a difference to try via VGA?

Why shall I use an HDMI switch?

Is there a plug&play solution for a HDMI retimer, cleaner? I just saw online an IC from TI like you wrote..

Thanks!

 

[FvM]

I see that using repeater chips isn't an option. Repeaters with HDMI connectors are available as retail products, but they don't necessarily improve the link if it's too far from expected transmission line parameters.

You can arrange copper rods as 100 ohm differential pair, ratio of center distance to rod radius in free air is 2.3, respectively rod clearance is 15 percent of diameter, rather close. Larger rod distance means higher transmission line impedance and would need customized repeaters. Up to 150 ohms transmission line (clearance is 75 % percent of diameter) might still work on short distances.

VGA signal bandwidth is much smaller. The signal is analog it won't be completely blocked by a bad transmission line bad possibly distorted.

 

[cyberctrl]

thanks for the detailed response! I tried with two HDMI-VGA adapters at each end but the signal didn't go through at all. But even cutting and reconnecting my HDMI does not seem to work. I find this very strange. See image.



https://obrazki.elektroda.pl/2640325200_1479921546.jpg

any other idea? many thanks.

- - - Updated - - -

would it be possible to extend cat5 or cat6 untwisted?
many thanks!

 

[cyberctrl]

So do you think it is possible to achieve one of the following:

- HDMi cable ---> 19 Copper Rods 1.5m placed in parallel ---> HDMi cable
- HDMI cable --> HDMI/Ethernet Adapter --> CAT6 ---> 8 Copper Rods 1.5m placed in parallel ---> CAT6---> HDMI/Ethernet Adapter --> HDMI cable

Unfortunately I lack the knowledge but do you think it is worth it seeking help from an EE to solve this?

Many thanks for your responses so far.

 

[marce]

Not really signal integrity is paramount with these sort of signals, just stick to the proper cables and connectors. I don't understand why you want the signal to go through the copper rods, even for artistic reasons, its going to mess up the signals, so forget the idea. I would look at a far simpler signal, say basic audio for going through some copper rods as you describe. The main problem is the signals are LVDS (low voltage differential signals) that need to be transmitted over twisted pair cables.
Have a look at return currents or even better a basic search for signal integrity (or differential signals over twisted pair cable) will provide some information on what is happening, though the concepts are a bit above basic understanding of signal propagation.