Coaxle or Component??

[Nienzus081]

What is best for running a video signal over long distances?? Used coaxle last night but it seemed to be a little screwy. It might have been a loose connection somewhere so I'm wondering what others are using???

[MoRpH]

By component I presume you mean like S-vid cabling, personally I stick with co-ax for long runs as component video has a tendancy to slip out of sync more frequently if there are ANY variables in the cable,etc..

[matdi]

I had the same problem with coax cable on long runs.If you have long runs than you should consider about buying video amplifier for long lines. I have one from Kramer Tools. And allso with video amplifier you will avoid ground loops. You can read all about ground loops here http://www.epanorama.net/documents/groundloop/index.html

[MoRpH]

Composite signal does not slip out of sync over distance like a component will. But yeah if you getting intereference some some where possibly due to signal weakness, VDAs are the go.

[charlielangridge]

The main thing to remeber (with any signal) is that it will weaken over distance, and you will need amplifiers. I am not sure if it is an option in video (Morph, correct me if im worng!) but balance signal is always the most stable and least susceptible analog signal. So used a balanced signal wherever u are!

[sleepytom]

there is no such thing as ballenced video signal

to do long runs without drop in quality the best soultion is a twisted pair encoder that will send video ballenced down CAT5 network cable - you get a pair of boxes one for each end and the composite or svideo plugs in to these.
see http://www.kramerelectronics.com/group5/index5.html

[matdi]

I think that coax cable shuold be the same impedence (Z) as video out from video mixer unit. So if I am not wrong it shuld be 75 ohms so on the end video signal is not 10 times or even more weakend. With ballenced video signal you could correct this problem. But ofcourse you should allso know the basic parameters of your coax cable so you can do some calculations in order to know which video amp. you should buy for your coax cables.

[MoRpH]

Well personally I have used long ethernet BNC/coax cable runs for video and even though some ppl think that its not compatible for video I have actually had more solid performance from them than most BNC/coax that is branded for video.

[Nienzus081]

So how long can you go without having to boost the signal??

[komart663]

well ,with a BNC cable you can have 25 meters at less ( i got a 25 m cable )and it works fine ,i think BNC can go till 50 meters but this distance is not very useful ,other way svid go till 10 meters ,i think 25 m is a max without amplfiers ,but i have a friend who works with analogic setup and svid cable 20 m long and it worxs fine ,the best is to experiment

[LEVLHED]

I've used S-Video cable of 100 feet with little trouble, and no DA.

[eXhale]

100-feet cables must be a mess to carry and store :)

[stevefromNewcastle]

I have between 100-200m of BNC cable I just went to the local DIY store and collected the old wooden reels that the electrical cables come on, now I just unwind as much as I need, and if it is wound back correctly the cable doesn?t even kink.
Steve
:p

[dronkie]

I have been using RG59 coaxial cable for years now in the video- rental business. And believe me : 25 meters is NOT the limit for an unboosted signal. You can easily have 50 or 100 meters out of a decent mixer. Of course you can't expect this from the composite-output of yer laptop, but just slip it into the mixer... Most of the problems come out of the difference of the electrical Phase your machinery is on. If your video-sources are on a different circuit then your projector, or if they are linked in ANY way with another circuit (even through audio, or just a small monitor somewhere else) groundloops can fuck up your signal. I find it very strange, but few people seem to recognize a groundloop-problem. They always think it's a weakened signal or so ...
Basicly : buy a decent cable. Don't use that horrible white stiff shit you're using at home for the TV, just because it's cheap. Spend a Euro per meter on a good cable (Belden, Sommer or Bedea cable) and buy some good connectors. It really helps.

Dronkie

[GreenHippo]

I agree about RG59. Most towns have an RS trade counter and you can buy a drum for a reasonable price. Cheap coax can also have a solid copper core which isn't intended to be used on the road. It will break after being flexed a few times. I know some of you guys do this for a hobby or on a shoestring budget. Try calling your local AV hire companies who do conference and exhibition work. Dodgy cabling is expensive when you're doing a product launch or big show cause your client won't pay if you don't display (pure poetry eh!?) so they tend to ditch perfectly good lengths of up to 50mtrs as a matter of course every 12-18months. A polite enquiry might land you all you need.

Avoid anything computer related even if it looks like video cable as its probably 50ohms when it should be 75ohms.

I've also used Sleepytoms top recommendation on CAT5 sytems at airshows with runs of several Kilometers. Its incredible but is more PRO due to its cost. However, that doesn't stop you from specifying it from the AV hire company if you are doing a festival or the like. If you tell them potential problems they will soon hire it in !

Also with grounding problems (ie source kit is on a different electrical phase than the display equpment - results in a slow horizontal bar running down or up your image) its worth carrying a video isolator in your kit (I think the humbucker or humbuckler (?) was the favourite). This will correct any earthing problems as it removes the physical connection and uses an induction loop process. (crikey, almost sounded like I knew what I was talking about then :p ). They are only the size of a packet of fags and are passive so you can put them in line anywhere. If you have several feeds consider one of the powered Kramer isolators as they come in 4 channel version (aimed at YUV or RGBS applications). Some people just drop one earth out of a fourway mains block but this won't help you with the insurance when you're standing with the fire officer in a smouldering heap of ashes that used to be a nightclub.

And finally, if you run two cables for Y/C (same as S-video) then make sure the cables are EXACTLY the same length or you will have problems that you will chase all night.

[GreenHippo]

While I remember, some low priced video cards are now shipping with SDI connections and many projectors have SDI inputs. Anyone tried using them in conjunction with each other yet?

[LEVLHED]

Originally posted by eXhale
100-feet cables must be a mess to carry and store :)

Oh my, yes its a terrible rat's nest no matter what you do with it. Thats why I've suggested before when buying them to only get 100' if you REALLY need 100'. I've found 100' is usually overkill in any setup.

[fluchtpunkt]

Originally posted by GreenHippo

Avoid anything computer related even if it looks like video cable as its probably 50ohms when it should be 75ohms.


yes computer coax (e.g. ethernet) cables have an impedance of 50ohms instead of 75ohms for video.
is there any (affordable) technology for digital video transmission. with digital transmission you can easily reach distances > 1km :), and with the correct setup there is (almost) no signal loss (...actually distortion as it's bits&bytes).

[MoRpH]

Originally posted by fluchtpunkt


yes computer coax (e.g. ethernet) cables have an impedance of 50ohms instead of 75ohms for video.

OK an exactly WHAT difference does that make to the video???? cause I have used them b4 and actually found them to be more reliable than some of the video coax I have used.

[fluchtpunkt]

Originally posted by MoRpH

OK an exactly WHAT difference does that make to the video????

a 50ohms cable will permit 1.5 times as much currency to flow than a 75ohms cable (with a given voltage between its ends). more currency means more friction which results in bigger energy-loss & therefor signal-loss (that's why electricity is transported cross country with high voltage & low currency).
the impedance is (more or less) to alternating currents what resistance is to direct currents. ohms is the unit for resistance though, impedance is measured in anonymous units! network cables (i take it you're referring to coax-ethernet cables) need to be terminated correctly because if they aren't, the signal is mirrored at the end of the cable & projected back to it - completely fucking up the entire signal in the cable.

[MoRpH]

Hmmm ok so that termination is the case when using them for ethernet, but I will state again that I have NEVER had a problem with using them for video, so maybe you can use ethernet for video just not video coax for eathernet :)

[fluchtpunkt]

yes. but ethernet-cables will have inferior behaviour (more signal loss?).

[MoRpH]

Hmmm inferior huh??? mmmmm well in this case, less problems with the cable not working (don't ask me I just brought it ages ago for a home network but it seems to stand up to coiling, etc... a LOT better than other coax), no noticable difference with signal quality from other (video standard) coax...... not sure how THAT is inferior???

[elbows]

Well its basic scientific fact that impedance is important, so according to the theory it is indeed bad to use non-75ohm cable. So there must be some real world factor that means you didnt have a problem, dunno what though :p

edit - I found this page, its to do with audio not video but it seems to fit with this whole theory vs what works in real life stuff...

http://www.rwonline.com/reference-room/wired-4-sound/rr-wired_for_sound23.shtml

[fluchtpunkt]

Originally posted by MoRpH
but it seems to stand up to coiling, etc... a LOT better than other coax...
...not sure how THAT is inferior???

...i've used computer-coax myself & didn't encounter any problems either - but it wasn't a complex setup they were used in (i.e. long cable runs, lots of electric equipment along the cables etc...) so i guess that doesn't have to mean much yet. in total (not necessarily always) the 50ohms cable will have inferior behaviour because it's not intended to be used with such hardware. ...and how easy it is to coil a cable has more to do with the rubber around it than its impedance :)

cheers

[MoRpH]

Yeah what I actually meant about the coiling is coiling it without breaking or damaging the core copper.

[sleepytom]

Originally posted by MoRpH
Hmmm inferior huh??? mmmmm well in this case, less problems with the cable not working (don't ask me I just brought it ages ago for a home network but it seems to stand up to coiling, etc... a LOT better than other coax), no noticable difference with signal quality from other (video standard) coax...... not sure how THAT is inferior???
there are 2 different things going on here - the durability of cable and its electrical performance.

the chances are that the 50 ohm network cable you have found to be more reliable is better quality cable (ie the screen and the casing and the conductors are made from better quality materials and thus stand up better to repeated use - they bend well and don't kink and the conductors don't break with repeated coiling)

how ever these 50ohm cables are not performing so well electronically - if you were to measure there signal loss over a long cable run you would be able to measure a drop in signal strength when compared to 75ohm video coax - the point is that this is a measurable performance loss not a perceivable performance loss (perhaps if you were using 2km runs you might be able to see the difference)

in short you will get a measurably better signal strength from using the correct impedance cable how ever this doesn't allways matter (especially on short runs) high quality cables designed for road use rather than installation will coil up better and last longer than cheap shitty cable - regardless of impedance

[Brainfade]

Component Video is not SVideo, Component has 3 x BNC plugs, 1 each fer Red,Green & Blue, its what virtually ALL highend Video gear has, SVideo is a step down, just like composite is a step down from SVideo, - this in Analogue Video altho they still use Component io in most highend Digital gear as well as Serial Digital Interface in the higher end & Firewire in the lower end.

[GreenHippo]

This all seems to be getting a bit scrappy despite the best intentions from all involved, so I thought a shortcut to somewhere might help. This was all I could find in the 5minutes available but seems a good starting point for those new to video formats or those like me who just wanted to check they where somewhere in the neighbourhood of being right! Covers video formats but doesn't answer the impedance question. Got to go with elbows on that. It just is. Otherwise it wouldn't be

http://techpubs.sgi.com/library/dynaweb_docs/0620/SGI_Developer/books/Ind2Vid_PG/sgi_html/apa.html:D

Sorry Elbows, you did the same with a page of info. Teach me to have a quick look at the forum then run out the door. Doh!

[burstingfist]

I bought an RF Modulator (50/75 ohm switchable) and an RF Distribution Amp with adjustable gain from radio shack. This improved the signal quality 100 fold. The resulting signal looked better than the house signal (VCR or cable)! I had been using the TVs without these components for a while (Straight out of a VCR), but the signal was totally shitty and intermittent.

[dronkie]

well, if you improved the signal with RF, that only says something about how bads it was before : We weren't even discussing the quality of RF, since it's even way beyond the quality of all the other videosignals. And for all the people who have never seen the effect of a 100 meters BNC with nothing connected at the end : try it. Hook up a cable that distance to the loop-through of a video monitor, and you'll see it. 75 ohms does exist, it's not a fable.

[vjTranceKoder]

From he looks of this article CAT5 is a fine choice:

What is a Balun? A balun is an impedance transformer that allows you to send a signal that requires a certain impedance value (such as 75 ohm for video) over a cable that has a different impedance (such as CAT5 that has 100 ohm impedance). You need one at each end, one to transform the original impedance to the impedance of the cable and the other to transform it back to the original impedance.

A VIDEO BALUN is the key component that allows you to transmit VGA, RGB, YPbPr. YCbCr, S-Video and Composite video or audio over Cat5. It's important to use video baluns when sending video over Cat5 since the impedance specifications of Cat5, Cat5e and Cat6 are 100 ohms. Video requires 75 ohm impedance and you'll introduce artifacts to your video without a balun. Basically, if there's an impedance mismatch the signal will be reflected from the receiver back to the transmitter causing delays in the signal transmission; the delays have a ghosting effect on the picture. It's like your TV on drugs.
-------

here is one for pretty cheap, two for $120USD.

http://www.svideo.com/svideobalun2.html

[alangeering]

Dude, this question was asked in 2002!
Better thing to do would be to write up more comprehensively the use of Cat5 Baluns and post it to VJC or as a new thread in VJF

[vjTranceKoder]

right you are! I have actually bought a pair of these badboys so Ill write a proper review after using them;)