Any DIY balun info for S-video to Cat5 conversion?

What is making the signal composite video going to do to help the OP ?

Graham

Hello Graham,

Not necessarily. With a good sync separator that does a fine black level clamp it is a little higher. As high as you can stomach WRT to black level droop for a single line, and even that can be compensated for to an extent after the balun.

Besides Doug DeMaw's book which, as Fred wrote, is out of print there is other material. Amidon and FairRite provide nice documents and many of them online. That's the ones I used to educate myself about magnetics a long time ago. I actually wore out one of the Amidon booklets.

Regards, Joerg

Hello Dave,

You did get some pointer. Need another one? Ok, here goes:

Don't let yourself become scared by the math. In the end it's easy and you can experiment if you take a larger core than needed.

Regards, Joerg

Viagra is better.

I've run composite video from a cam ~100' on cat 3 phone wire with out issue. Never tried s-video on phone wire. If s-video won't work on 125' of phone wire, he has a possible alternative to convert to composite from s-video to give it a try.

Hello Graham,

With a sync separator. That's built into the monitor if it is designed to receive composite. However, there are huge performance differences. Seems that some engineers in companies that design monitors haven't fully understood the concept or haven't figured out how to handle it during the vertical sync phase. So yes, you do see trouble in some monitors when the path doesn't reach down to a few ten Hertz. But those are poorly designed.

I meant passive parts.

There is no DC component while composite video is being transmitted. It is restored by clamping.

Regards, Joerg

Errr, so how do you deal with the syncs then ?

I see you're talking about further processing which kinda cancels the point of shoving the video down Cat 5. Might as well buy the coax !

Then there's also the net DC component to consider.

Graham

Actually, what you say makes sense to me. I was coming to the same conclusion myself.

Maybe the OP was concerned about an impedance mismatch from 75 ohm coax ? Isn't Cat 5 around 100 ohms ? I can't actually see a short run with say ~

6MHz as the top frequency being too troubled over a short length.

I reckon it's worth trying before bothering with anything more complex.

Graham

Net DC, nope, video is generally clamped, often about where the burst thingummy is. This sets the black level. You only really need to keep the clamp (DCish) for a video line. Thats one of the nice things about video, it's analogue with gaps in it

martin

Helps with the sunburn, doesn't it

martin

Phil, first off I was responding to Dimitri, or are you Dimitri on another person's PC?

On Sat, 3 Sep 2005 12:39:34 +1000, "Phil Allison"

I did ASK for construction/design information did I not (read the title of this thread)? So far my exposure to baluns I've ever seen in a device has been a ferrite core with a few turns of wire or a prebuilt, off the shelf module from a vendor. Not a stretch to believe that a s-video to cat5e would be too much different. In reality it may be, but conceptually it isn't "out of touch".

WTH? Now why would I do that?! Quite a leap there. If I can build them, I don't need to buy commercial ones. If I can't build them, and commercial ones are too expensive for a given solution, then I'll run RG6 or even wirelessly transmit. Many different choices. I don't steal Phil.

Thanks for stating in another way what I just said.

Because I'm not worried about shielding. I'm worried about reflections due to impedance mismatch creating visible distortion in the video signal.

Phil, if I buy one of those $70 pairs, take it apart and find a ferrite core inside with a few turns of wire and a MADE IN CHINA sticker inside I'm going to be pissed at you! :-)

Dave

Hmmm, HF loss aint that bad compared to the refections in the cable, gives you ghosting, double/multiple edges etc. Cant be bothered to remember the arithmetic, but one PAL line is 64uS, work out how far a reflection in terms of screen width would need to be to cause visible imparment. The OP was going to project this on a big screen, maybe be he has some good quality material.

This is just a bodge, all for a few bucks.

martin

Ah ! Now we know. I guessed it might be an impedance thing that was troubling you most.

Why not just hook your video up to some Cat 5 and try it ?

You're only talking about 75 ohms vs ~ 100 ohms IIRC.

And Phil's just a jerk btw. Ignore him.

Graham

Analysis of how baluns work is a very complicated procedure. Consruction is the most simple imaginable. Just wind a few turns around a ferrite ring.

Only made possible by the invention of ferrites. Which I think happened in occupied Holland during the carnage and destruction of WW2. It amazes me how engineers managed to concentrate their minds on the subject.

--
Reg.

On Sun, 04 Sep 2005 05:13:02 +0100, Pooh Bear

Yeah but he's got a reason - he's an Aussie!

An optical engineer and his American wife that worked with me went back to Australia after being RIF'd. His wife after being there after a bit realized that it's not her husband that gruff, it's all Aussies. Just part of the culture. 'Mates' great each other with a "F-off".

Dave

An SS storm-trooper with a submachine gun at the lab door and the prospect of being sent to a concentration camp if you fail concentrates the engineer's mind wonderfully ...

--
"Electricity is of two kinds, positive and negative. The difference
is, I presume, that one comes a little more expensive, but is more
durable; the other is a cheaper thing, but the moths get into it."
                                             (Stephen Leacock)

"Dave"

** Who cares - this is a pubic forum, asshole. ** You are begging for it.

** Nonsense.

** Seems a logical enough solution when all the other options for a low cost solution are rejected. ** You will never know if you keep refusing to try.

** Obviously we are dealing with the usual sort of mental retard that climbs ladders and pulls cable through conduits.

Closer to apes than humans.

......... Phil

prospect

===================================

Utter rubbish.

The Germans had more sense than to ill-treat the more profitable of the dutch civilians. Even if you were a Jew.

The materials design engineers and all others scientists, were encouraged and well paid to carry on with the jobs they loved best. And so they behaved accordingly. They couldn't help it! What would you do?

====================================

They are very strange ppl.

The last Alpha Male will doubtless be Aussie.

Graham