HDMI over CAT7

[TimmyTee]

Hi All,

 

I got a cheap gizmo from Amazon THIS* for use in an upcoming show where we want to project backdrops. We don't have an amazing projector, we paid for short-throw at the cost of image quality, but it's more than adequate for our needs. As the tech desk will be some distance from the projector, this seemed an ideal solution, also the local HDMI port allows a monitor to mirror the projector output, very handy when you can only see 25% of the back of the stage. I opted for this model as it offered 60 metres over CAT6 or superior cable.

 

I tried it with an old 1-metre long CAT5e cable, my laptop and my TV and all worked very well. However, I made up an ethernet cable using CAT7 and standard RJ45s and although the 2 units light up correctly (power and signal reaching the receiver) I get nothing on the TV. The reset button on the receiver made no difference.

 

My first suspicion was the cable, I hate making up ethernet cables! But that tested fine between my laptop and my router, I got a 1GBPS test on fast.com, I didn't know I had such a fast connection!

 

My question to those who are more clued up than me (not a very exclusive club), is whether there may be a different wiring standard needed for the ethernet cable? Or have I just got a duff bit of kit?

 

As ever, thanks in advance for any help or advice on this.

 

 

* not exactly the same, I got mine on Spanish Amazon but posted an English link, the actual item is THIS

[Dave m]

Have you tried the 1M cable with adaptors next to the projector?

The device may put out a version of hdmi that the projector doesn’t like?

 

 

It’s possible that the devices can’t cope with such a long run, or it could be the cable choice, or construction.

I’d ensure it works on short runs then increasingly long known good tables

[mi-ul]

What length was the cable you made up? The cynic in me would be pleased at this device working beyond 40m or so

You added standard RJ45 connectors - are they shielded, is there a shield connection between the two connectors on a multimeter?

What resolution are you sending - I'm guessing 1080, does it work at 720?

[TimmyTee]

It was a 50m cable, standard non-shield connectors.

 

I'll try with shielded ones, after sending a lower res.

 

All good tips.

 

Cheers!

[Anothertom]

Those non-brand Chinese hdmi extenders at notoriously terrible. And only having power at the sender is just asking for trouble. If you wanted to extend over cat6/7 then you should be looking for a more reputable HDbaseT box (e.g. liteware, from personal experience). Those would be significantly more expensive, but will reliably work. Lower quality sender/receivers might work at lower resolutions but you might get intermittent drop outs. Performance is also more related to CSA of the cable than anything else afaik, as it's not IP traffic and not bound by that standard.

 

The (preferred) alternative would be to get some hdmi-sdi converters (blackmagic micro converters for the cheaper end of this) and run in an SDI line to the projector, if you want a local preview then a cheap HDMI splitter would be the solution.

[richardash1981]

Some thoughts:

• Ethernet often only uses two pairs out of the four in the cable (well, 10 Mbbps and 100 Mbps only ever use two, 1 Gbps uses all four), so some cable faults can go undetected using Ethernet as a "test". Sending HDMI is going to use all four pairs.
• The specification is similar to that for HDbaseT, although as it doesn't mention that standard it's almost certainly not fully compliant. But you can expect it to be doing much the same thing, including running the cable pairs significantly faster than Ethernet does and relying on active cable compensation to make up for large cable losses (which is why the length limits go down with lower grade cable).
• As mi-ul noted, the screen connection might matter (although if it really works with CAT-5 cable, then screened ones of those are very rare)
• CAT-7 cable usually has different colours for the cores (no more stripy cores), but it's still important that the same pairs of pins use the two wires from a single pair. In other words, don't (as I once did) wire 1-2, 3-4, 5-6, 7-8!

If you are on a tight budget, you could look around for decent HDbaseT units on ebay - they don't have to be a manufacturer matched pair if they are HDbaseT compliant, and generally replacement power supplies are easy to arrange (most seem to run on 5V, and the receivers use lots of current). For your cable length, "HDbaseT Lite" would probably be OK, although it's a bit marginal if you do need 60m cable run.

 

[TimmyTee]

Update

 

I just tested the device using a forgotten 30m cable, I don't know the spec, it was 7€ on amazon panic-bought to allow me a cable connection while working from home during the lockdown. It worked perfectly with my laptop in the living room and a monitor at the other end of my flat. I am impressed with the quality in fact.

 

I think it's the cable that is at fault then. I had no idea the connectors were so important, it's got to be 14 years since I last wired a network.

 

To those that recommended other units, I fully agree, you get what you pay for. Unfortunately, our little am-dram company suffered a break-in to our store and we lost a lot of equipment that we'd built up over the years, buying good gear as and when the funds allowed. It exposed a massive loophole in our insurance, we weren't covered. Now we're in a situation of having to buy a lot of equipment on a limited budget. I'm stuck with these baked bean cans and bits of string for the time being.

 

Richardash1981, you confirmed what I suspected, differing protocols for ethernet and this set-up. I take your point about the screened connectors, it does indeed work over much more basic cables, now successfully tested on a bargain bucket 30m cable. I suspect that I messed up the connections rather than the connectors themselves being at fault. Thanks for your wisdom. You're also right about the colour coding, I don't know if this is typical, but the pairs are foil-wrapped, blue+white, brown+white, green+white and orange+white. They are horrible to check before crimping the connector on, how do you know if you've swapped a white by mistake?

 

I am mystified a little though, I got a 1 Gbps result when doing my ethernet test, you say 1 Gbps uses all 4, this suggests that all 4 pairs are correct. Ethernet must be more forgiving than these little boxes, I guess

 

Also, if these things are working with an off-the-shelf ethernet cable, it says to me a standard crossover ethernet cable will do the job.

 

All roads lead to Rome. Rome being my ham-fisted cable-making. Time to try again, my only concern is that with too much trial and error, my 50m cable will end up at 3m and there'll be a huge pile of discarded connectors.

 

Once again, blue-room comes up trumps. Aside from the sage advice, just setting things out here has helped me clarify a lot of things, albeit in a rambling train of thought.

 

Cheers all, this has helped me enormously and hopefully, it may help someone else in the future.

 

• but it's still important that the same pairs of pins use the two wires from a single pair. In other words, don't (as I once did) wire 1-2, 3-4, 5-6, 7-8!

 

 

Hold on. I've just read this again. If I've read correctly, I shouldn't need to do a crossover. As long as the pairs match, eg blue to 1 and its white to 2, orange to 3 and its white to 4, etc. it should be OK. Am I right?

 

What the hell, I'm going to try it!

[sunray]

Update

 

 

Hold on. I've just read this again. If I've read correctly, I shouldn't need to do a crossover. As long as the pairs match, eg blue to 1 and its white to 2, orange to 3 and its white to 4, etc. it should be OK. Am I right?

 

What the hell, I'm going to try it!

Well that's where you are going wrong.

the pairs are 1&2, 3&6, 4&5, 7&8

There are several standards but as long as the pairs are correct and the same colours at each end it should work.

I stick with:

 

1 = white orange 2 = orange, 3 = white green,

4 = blue, 5 = white blue, 6 = green, 7 = white brown, 8 = brown.

Which is I believe the EANSI/TIA 568B standard. A crossover cable simply swaps the orange and green pairs viZ:

1 = white green, 2 = green, 3 = white orange,

4 = blue,

5 = white blue,

6 = orange, 7 = white brown,

8 = brown. Which is I believe the EANSI/TIA 568A standard. Originally most cables were made as a crossover with 568A at one end and 568B at the other but that requirement is extremely rare these days.

Not that it matters but there is a tiny chance I've mixed 568A and 568B EDIT: I give up trying to understand the vagueries of CR's on this site.

Edited October 17, 2021 by sunray

[TimmyTee]

Update

 

 

Hold on. I've just read this again. If I've read correctly, I shouldn't need to do a crossover. As long as the pairs match, eg blue to 1 and its white to 2, orange to 3 and its white to 4, etc. it should be OK. Am I right?

 

What the hell, I'm going to try it!

Well that's where you are going wrong.

the pairs are 1&2, 3&6, 4&5, 7&8

There are several standards but as long as the pairs are correct and the same colours at each end it should work.

I stick with:

 

1 = white orange 2 = orange, 3 = white green,

4 = blue, 5 = white blue, 6 = green, 7 = white brown, 8 = brown.

Which is I believe the EANSI/TIA 568B standard. A crossover cable simply swaps the orange and green pairs viZ:

1 = white green, 2 = green, 3 = white orange,

4 = blue,

5 = white blue,

6 = orange, 7 = white brown,

8 = brown. Which is I believe the EANSI/TIA 568A standard. Originally most cables were made as a crossover with 568A at one end and 568B at the other but that requirement is extremely rare these days.

Not that it matters but there is a tiny chance I've mixed 568A and 568B EDIT: I give up trying to understand the vagueries of CR's on this site.

 

Yes. I think we were talking about the same thing but using different words. I have now tried a "straight-through" cable set-up. 1 to 1, 2 to 2, etc. As you say, the colours are irrelevant. I then went mad traying to swap out different connections, to no avail. I then went on to compare a working cable with my own, they bothe were "straight-through" but..... I found a dodgy connector on my one, pin 1 wasn't giving a connection, excess plastic it looked like. After swapping that out and another continuity test for good measure, I plugged it all in and..... IT DIDN'T WORK.

 

All roads didn't lead to Rome, my cabling is fine. The roads now lead to China! I think the magic boxes can't handle 50m.

 

Thanks again all for your help. Let's see how they respond to my support request, they've acknowledged it and are "checking with their engineers".

[DrV]

I have now tried a "straight-through" cable set-up. 1 to 1, 2 to 2, etc. As you say, the colours are irrelevant.

At risk of repeating something which has already been stated,

the colours are NOT irrelevant. You MUST maintain the pairs. Sure it doesn't matter if you use the brown/brown & white pair on pins 1&2 or on 7&8 but you mustn't, for example, use brown on pin 1 and brown&white on pin 8 as those two colours are twisted together. Whatever colours you use, the wires on pins 1 and 2 must be twisted together. The same applies to all the other pairs which Sunray listed above.

[sunray]

Update

 

 

Hold on. I've just read this again. If I've read correctly, I shouldn't need to do a crossover. As long as the pairs match, eg blue to 1 and its white to 2, orange to 3 and its white to 4, etc. it should be OK. Am I right?

 

What the hell, I'm going to try it!

Well that's where you are going wrong.

the pairs are 1&2, 3&6, 4&5, 7&8

There are several standards but as long as the pairs are correct and the same colours at each end it should work.

I stick with:

 

1 = white orange 2 = orange, 3 = white green,

4 = blue, 5 = white blue, 6 = green, 7 = white brown, 8 = brown.

Which is I believe the EANSI/TIA 568B standard. A crossover cable simply swaps the orange and green pairs viZ:

1 = white green, 2 = green, 3 = white orange,

4 = blue,

5 = white blue,

6 = orange, 7 = white brown,

8 = brown. Which is I believe the EANSI/TIA 568A standard. Originally most cables were made as a crossover with 568A at one end and 568B at the other but that requirement is extremely rare these days.

Not that it matters but there is a tiny chance I've mixed 568A and 568B EDIT: I give up trying to understand the vagueries of CR's on this site.

 

Yes. I think we were talking about the same thing but using different words. I have now tried a "straight-through" cable set-up. 1 to 1, 2 to 2, etc. As you say, the colours are irrelevant. I then went mad traying to swap out different connections, to no avail. I then went on to compare a working cable with my own, they bothe were "straight-through" but..... I found a dodgy connector on my one, pin 1 wasn't giving a connection, excess plastic it looked like. After swapping that out and another continuity test for good measure, I plugged it all in and..... IT DIDN'T WORK.

 

All roads didn't lead to Rome, my cabling is fine. The roads now lead to China! I think the magic boxes can't handle 50m.

 

Thanks again all for your help. Let's see how they respond to my support request, they've acknowledged it and are "checking with their engineers".

Whoa there, slow down a minute I'm hearing alarm bells.

First off the colours are irrelevant (Sorry Dave) but the pairs are very important, very important. However I'll use colours to describe the layout, Also using this layout the colours will fall into place easily.

You will see the centre 2 pins, 4&5, are a pair (both blues) and each side of that in pins 3&6 is another pair (both greens). To one side of those pins 1&2 is a pair (Both oranges) and to the other side in pins 7&8 is the brown pair. That positioning of the 4 pairs is super critical and if you don't maintain that the VGA extender will simply not work.

 

 

Next alarm ringing...

excess plastic it looked like

Are you stripping the insulation off the wires? Don't you will never get it to work. Edited October 17, 2021 by sunray

[TimmyTee]

Don't worry, I learned not to strip the individual wires many years ago. The excess plastic was covering pin 1 of one of the connectors, I noticed this when the probe from my continuity tester wasn't making a contact.

 

With a new connector in place, I did a continuity check again, pin 1 is connected to pin 1, pin 2 to pin 2, etc. This matched exactly what was happening on a short Cat5 working cable.

 

I'm confident the problem doesn't lie with the cable, but to rule that out completely, I'm going to make a 2m version and test that. I won't be needing the full 50m of the roll I bought, I think 40m will be sufficient.

 

That will have to wait though, I have to get some work that I actually get paid for out of the way first.

 

I'm typing this on my TV, my 2m homemade cable works. It's not me, it's the boxes.

 

The Chinese vendor has been back in touch. They say the description is wrong and it can't achieve the 50m. By way of an apology, they are sending me a 100m unit free of charge.

 

I really can't complain about that. Providing it works!

[sunray]

Just to confirm the colour relevance; the first time I terminated 8p8c plugs on cable, the venue used the alphabetical sequence: blue, white, brown, green, white, white, orange, white. and I stuck with that for a while.

That was until I modified some manufactured cables; I had to cut the end off, poke it through a hole and fit a new plug. For that job I wrote the sequence on a piece of white plastic tape on the enclosure I was adding these to then clearing up I removed the tape and put it the handle of my crimpers where it's resided for the last 15 years or so.

[TimmyTee]

Just to confirm the colour relevance; the first time I terminated 8p8c plugs on cable, the venue used the alphabetical sequence: blue, white, brown, green, white, white, orange, white. and I stuck with that for a while.

That was until I modified some manufactured cables; I had to cut the end off, poke it through a hole and fit a new plug. For that job I wrote the sequence on a piece of white plastic tape on the enclosure I was adding these to then clearing up I removed the tape and put it the handle of my crimpers where it's resided for the last 15 years or so.

 

Absolutely. If anyone else is going to modify your cabling, then colour coding is essential. Or if you don't have sight of both ends. Otherwise, the signals that pass through are colourblind.

 

When I first arrived in Spain and started work as a spark, I saw some horrifying things. A domestic junction box with all black cables, for example. Another one I heard of was a guy that was in a flat with no earth connection, he had a local electrician in while he was away with the brief to install an earth cable in all sockets. He came back to find the entire apartment rewired in green/yellow cable, but still no earth connection.

[J Pearce]

Otherwise, the signals that pass through are colourblind.

 

But not pair blind. It is important that pairs of signals remain on twisted pairs. Just because a cable passes a dc current does not mean it will pass a signal at 250MHz or 500MHz.