connecting PC to TV

Maybe?

Now you just have to worry about audio. If you had coax all over the house it would be a piece of cake.

CIAO!

Ed N.

There is no need for coax for audio. Better without coax.

google 'svideo balun' for the other 37,000 hits..

Huh ? Unless you either have a balanced driver / receiver with proper twisted cable inbetween or you are transporting audio at speaker levels, you will NEED some kind of coax :-)

(Or the sound on any program will be very boring: 60 Hz :-)

The links previously given are for baluns designed for the transport of audio and video signals over category 5 twisted pair cabling.

A balun is a device designed to convert between balanced and unbalanced electrical signals, such as between coaxial cable and twin-lead.

Yes, thank you. I know what a balun is :-)

It is the 'better without coax' part that I don't understand.

Would a double balun with twisted-pair in between outperform a straight coax connection on TV-audio ?

Actually, I doubt that. On audio frequencies and levels, a 'simple balun' requires a complete mu-metal encased transformer. Otherwise, just the transformers themself both would pick up as much noise as the twisted pair suppresses :-) And this arrangement would still suffer from rather huge losses, both in level and sound quality. My 2 cents :-)

Yes it will. Besides, in many cases a high(er) end audio equipment will expect ALREADY BALANCED line level input, so you can drop the second balun or else you have to provide one for your common mode coax signal.

It was a very good point but you had a wrong conclusion made. In ANY balanced-signal transmission over any cable that's worth buying these days, the active equipment will be MUCH more susceptible to EMI than the cable. Besides, EMI can also (big times!) enter the active equipment via its power cables. However, it should always be assumed that the active device bears FCC or EC EMI compatibility approval label else just drop that one and go buy the approved one. Therefore, you can let electronics designers worry about EMI shielding INSIDE the boxes (what a daunting task that is!) and concentrate on laying your cables away from apparent EMI sources and installing it properly to avoid any physical damage that would ruin the balance.

And, just to finish it off: in some cases baluns aren't too practical given cost, reliability (can be torn off the patch cable), size or other considerations. As a result we end up sending line level audio signals and composite video via a CAT5E cable without ANY baluns (up to 100 feet), and no visual picture or audible sound degradation can be found. I'm not talking about concert halls, obviously, so, if you have "golden ears", please DO take care of balancing the signals before sending them over UTP.

Which is fine if you just want to go to one outlet AND the TV has available A/V inputs. If no available inputs, then you have to either use an A/V A/B switch or modulate at the TV set. If you want to be able to watch the PC at more than 1 TV, then you need a distribution amplifier that has several outputs. Then you're faced with the same A/V input situation at every TV set. You also need to make sure there is a terminator on every unused outlet. If not, reflections abound.

Much easier to modulate at the PC (to an unused CATV/UHF channel) and combine it with the cable/satellite distribution system where it becomes available at all outlets in the house.

CIAO!

Ed N.

If you do that, you'd better make sure it's not leaving the house. Cable companies take a dim view of unauthorized signals on their cable.

Well, this puzzled me. I would expect sound to be very noisy (because of lack of shielding) and video to be ghosty (for lack of proper termination). And the only way I could come up with involved a soldering iron :-)

Just to see it for myself, I wired 2 SCART to RJ45 yigs.

First with 3 feet of cat5 cable, later with 25" cat5 cable. I must admit: I'm astonished. This is quite acceptable.

Quite a learning experience! Thanks!

It's entirely possible to build a transformerless "balun" with op-amps, that are configured to convert balanced to unbalanced and reverse. They can also provide gain and have a frequency response going down to DC. Anyone working with instrumentation would be familiar with such applications.

Twisted pairs have been used for many years, in a variety of applications, because it does work so well and avoids the ground loop problems of unbalanced shielded cables.

Well, the original request was for a means of sending the signal from his PC to his TV over UTP cabling, for which the baluns will do just fine.

The original poster did not ask for a means of distributing the signal to multiple TV's throughout the house, which can be done in several ways, such as DA's feeding baluns or direct connections, or via a modulated signal.

With a direct connection you can control who gets to watch the signal, it's a bit harder with RF. This might be a factor depending on the content.

Easier, but not as high quality as a component, s-video or composite video connection. If not done properly, the signal can leak upstream, which may not be desirable.

I would rank the various signal types in terms of quality as follows: 1. digital 2. component 3. s-video/YC 4. composite 5. RF

Advantages of direct connections: signal quality, access control

Disadvantages: requires discrete input at each tv for each source, or a switcher.

Advantages of RF: multiple signals on the same wire, ability to use with any TV.

Disadvantages: signal quality, possible leakage upstream, inablity to control access.

I initially figured that the device was such a beast.

But

points to a device that is described as 'passive' and does not require any power.

Have yet to find a chipset to cover that specs :-)

Some practical experiments I made after my posting show, that twisted pair performs remarkably well, even on unbalanced sound.

And more astonishing, composite video over 25 feet of twisted pair shows no visual degradation despite the lack of balancing and proper impedance matching. Guess I'm learning. Every day, still :-)

But even on unbalanced signals, it appears to perform very well.

Given the comments made by Dmitri I created a 25 ' SCART to SCART connection, using twisted pair cable. Violating almost all I 'know' about such connections:

- no shielding

- asymmetrical signal on symmetrical cable

- 110 ohms cable in a 75 ohms system

- There are 3 different ground connections in the cable

You are welcome! I'm glad I could kick in some fresh ideas ;-)

That would depend entirely on how you design the circuit. The nice thing about op amps, is that it's very easy to set the gain and impedance to whatever you want (within the capabilities of the device). If configured for low or gain and input impedance, noise would not be a significant problem.

Op amps would have probably worked similar or better in most cases, but, simply because they require power (sometimes even two supplies, depending on the actual part), it is much more practical to build a balun on a transformer that's capable of working on frequencies your application requires. It is actually the reason you need to have a wide variety of baluns for every application, not just one model for any asymmetrical-to-symmetrical situation. One other thing to consider would be this: Op amp would probably be TOO SENSITIVE for the task, and would amplify the noise as well as the useful signal. That can be handled by filters, but the circuitry tends to grow unnecessarily complex. With transformers some loss is actually healthy 'cause it filters out the noise.