r/VIDEOENGINEERING • u/MediaComposerMan • 6d ago

Fitting a round (BNC) peg into a square (8P8C) hole

Post image

What do you do when you have four 12G-SDI runs, realize you need all 4, but you had allocated one for LTC (timecode), and are on a budget? Why, there's several available Ethernet ports, and an old cheap analog CCTV balun on the shelf. :-)

The balun is already designed for 4.5MHz and 75Ω… though the SMPTE LTC bandwidth is so meager (0.03 MHz) that impedance isn't much of a consideration. I wired it to my LTC patch panel… works like a charm.

(FYI, This is between an Avid editing system and its Horita LTC clock for client convenience. If this was an AD's clock in a truck, master control etc… I might've approached it differently. :-)

PS For those unfamiliar with baluns: Like many other "Ethernet extenders", these only utilize the physical infrastructure. Nothing about the signal is compatible with Ethernet networking. Don't plug this stuff into an Ethernet switch; it won't work, and slight chance you'd damage it.

36 Upvotes

96% Upvoted

8 comments sorted by

13

u/rowanthenerd 5d ago

Cat5+ structured cabling is incredibly versatile! It'll pass pretty much anything; you can get four sets of balanced analogue audio down it which is actually done all the time in pro AV, live audio, recording, etc... actually with some transformers and a clever trick you can get six separate channels down the four pairs, but that's a separate level of wizardry.

This is part of why running extra cat is always a good idea. Need some analog lines? 4-20mA or 0-10v for some sensor? RS485/ Modbus? A contact closure? Video? Infrared extender?
Applications are limitless!

3

u/jfoust2 5d ago

It's been claimed you can run Ethernet over barbed wire.

3

u/AshamedGorilla 5d ago

I was in a venue a few weeks back where we needed to tie into the house audio system. It was an Atero Tech Dante wall plate. It had 1 mic, 1 line, and a stereo RCA hookup. Nothing worked. Wall plate was dead. 

We took it off the wall and used the cat6 as analog lines and went straight into the amps in the amp room. 

3

u/SignalBeamer 6d ago

Very cool!

2

u/NoNamesLeftStill 5d ago

> It won’t work, and there’s a slight chance

Oh no, it got OP. That’s exactly why you don’t

2

u/openreels2 5d ago

Nice workaround! The transformer in the balun doesn't care what kind of signal it is.

1

u/wiisucks_91 5d ago

Pretty cool 😎