I'm a little confused too as every video engineer that I've ever worked with insists on 100% copper center for baseband video. Perhaps it has something to do with the fact that while a video signal might be similar in frequency to the lower side of a CATV signal the signal format is different.

Either way I've seen plenty of people get away with it. Luckily most people don't have a clue what a good picture looks like so minor color shifts don't bother them. However I've seen some very odd problems result from poor terminations.

either way we are all in agreement that an impedance matched 75 ohm base band video signal cannot be split without a buffer amp. This is why good video equipment has a switch for hiZ or terminated on the loop outputs.

As someone else said - a 2x3 is a matrix switch, not a distribution amp.

I second the idea of simply hooking up the existing cables directly between the source and the display as that is the best the picture is going to be with the existing cable. Even with the wrong cable run I can't imagine that the difference is going to be DRASTICALLY different as a video signal with a "Y" cable in the signal path is often so wrong that the display can't even lock sync.

Inday makes a pretty nice YPbPr 1x4 DA for less than $200.

Most everybody here is pretty darn right.

The whole 450 MHz talk is nonsense for this discussion because we aren't talking about upper TV channels, we are talking about baseband video. CCS will attenuate video signals more than solid copper because skin effect won't come into play until the higher frequencies of HD signals come into play, that is, PICTURE DETAIL. It is worth looking at the picture with the CCS once the other problems are solved, to see if you have to change out the wire. You might not have to, despite good theory to the contrary.

Since we have already seen "splitter" when "Y-cable" is meant, let me point out that "video" does not mean that stuff that comes in from the antenna. There still are "video switches" out there that use F connectors because they are switching RF, not video.

About the ghosting -- I was first thinking that one of the monitors might be set to high-impedance input, which would reflect the signal back, but I don't think so. The ghosting does mean signal is reflected back from somewhere, but that comes from impedance mismatch of any sort, and your Y cable feeds a 75 ohm source to a 37.5 ohm load; that mismatch should cause ghosting. If one of the monitors were set to high impedance inputs, well, a) it would be unique in the world of consumer electronics and b) you wouldn't have a signal level problem.

OK gang, thanks for all the input. Based on what we've discussed, I think I've put the plan together as follows:

1) Using the Zektor as a switch box, use a 1x3 Key Digital distribution amplifier from the output of the Zektor into the amplifier, then out to the sources.

2) If I STILL have ringing/reflections, replace the cable (assuming it's CCS) with more appropriate SC.

3) If I'm unable to resolve based on above, discuss local-sourcing equipment into the room.

Did I miss anything?

Thanks again for all the feedback.

Fred

By Video Engineer you mean the Tech at a TV studio? I wouldn't call him an engineer in most cases, as most have never had any electrical engineering.

Copper will have lower loss per ft than copper covered steel at low frequencies. Note that this will show up in the specs for the cable, as good cable manufacturers (like Belden) spec loss per ft across the entire frequency spectrum the cable is designed for.

Note that another difference between most RG-6Quad CCS and RG-59 solid copper is the shield. Most RG-6Quad has 4 shield layers, 2 layers of 100% aluminum foil, and 2 layers of aluminum braid at about 60%. RG-59 solid copper usually relies on copper braid with coverage in the area of 80 to 100%. The aluminum is less conductive, but there is more of it there, and resistance is a function of the impedance per sq of the material, and the cross sectional area. In many cases the cross sectional area of the aluminum shield, and the better shield coverage can result in better signal.

The RG-6 will also exhibit lower dielectric loss, as the cable is thicker, allowing for a larger dielectric, therby reducing the loss. Cable manufacture also allows for some fixed values for accuracy for how consistent the dielectric layer is. For a larger cable, this variation will be a smaller percentage, resulting in a more even impedance over the length of the cable, resulting in fewer reflections, and better power transfer.

So, to compage RG-6Q CCS to RG-59 SC is not so simple. You really need to look at the specs for the loss per foot over the entire frequency range of the cable. This is part of the reason so many misconceptions apply about this area. Most people don't really understand the trade offs, and will fall back to the position that always works. Nothing wrong with this, but in a case where something is already pulled in the wall, the misconceptions can lead to lots of wasted time, money, and effort.


Poor terminations are an entirely seperate discussion from the cable type. The best cable in the word, improperly terminated will give horrible results. So what's your point?


I love that you refer to RG-6Q as "wrong cable"! For the reasons I give above, predicting if good quality RG-6Q CCS will give better or worse performance than RG-59 SC is not so straight forward. It will depend on the length run, and the characteristics of the particular cables in competition. This doesn't mean the outcome isn't predictible, as it is. But since we don't know the manufacturer of the RG-6Q in question, we don't know how good it is.

I tend to give everyone on this board the benefit of the doubt until proven otherwise. Perhaps In your eyes I have already proved myself to be an idiot. Regardless I find this insulting. An engineering degree in your hat doesn't necessarily mean a damn thing if you haven't actually dealt with the real world results. I've known plenty of engineers that can work the math and the theory all day long but have never seen the real world results and often don't have any understanding of why some of those real world results are DRASTICALY different from what their math tells them it should be. Occasionaly this is because of some real world issue that us uneducated tech school wire monkeys in the field could have told them about twenty years ago, if they had just troubled themselves to ask.

As for the peple I was specifically referring to you can call ANY competant company that sells video products and pretty much everyone from the design engineers down to the secretary will tell you that the industry standard for base band video is solid copper center. Wether it's RG59 or RG6 or mini RGB would depend on the application but the only place I have ever seen it suggested that CATV wire is fine for an HD component run is on this board.

The individual that I was primarily refferring to does have the degree and is responsible for several cable television company head end designs for the video content, on demand content, broadband internet delivery and telephony delivery and he actually gets down and helps build the racks himself. Would you consider him qualified?

You can tell us about your degree and your math all day but I find it to be irresponsible to suggest anything other than the fact that the wrong cable was pulled. QQQ has posted several times recently about how our fledgling industry is to be perceived in the world. We like to complain all the time about sparky pulling zip cord for speaker wire, even though electrically it works just fine, but now it's OK to say that CATV wire used in place of CCTV wire is just fine? Sure it is if you're are not interested in following industry standards and if you would like our industry to be perceived as hacks because we can't even bother ourselves to pull the cable designed for the job.

This is part of the reason

I never suggested that he rip the cable out but I most definately would like to see my competitors use the industry standard cable on future projects.

To the board at large. Unless I'm discussing the proper way to drink beer please disregard anything I might post as irrelevant. I don't actually have a legitimate degree in drinking beer and there is no doubt that my spelling and grammar get even worse after drinking beer, but I have been given an honorary degree from several local watering holes after putting in a sufficient number of hours. I focussed primarily on Irish and German beer but I hope to add several more minor degrees in the years to come.


I guess I didn't make myself clear enough, although I wasn't replying to you directly. My point was that, while I beleive the wrong cable was used, in the length of run we are talking about the more likely real world problem is going to be from poor terminations, although the systems I've personally seen where CATV wire was used for component video the picture pretty much looked soft and flat regardlesss of the termination.

This is also why I suggested to first connect the source directly to the display as this would be your base point. Assuming the video run isn't a lot longer than we are all assuming this is the best the picture is going to get regardless of what matrix switch or distribution amp you are going to employ. If this direct connection doesn't satisfy the customer then all the remedy work is going to be hard to get payed for. When cleaning up someone elses problem I like to find a way to create a realistic expectation. I find customers are generally very upset to pay for a job twice only to still be unhappy with the results.

I love the fact that you continue to discuss cable design as if somehow industry standards and repeatability are irrelevant due to the fact that the wire was already pulled. I often urge people to use Belden cable actually intended for component video distribution as I believe that provides the most proffesional results but the only time I really feel the "wrong" cable was pulled is when CATV wire was used for component video

If memory serves the ampacity of a 14awg conductor with a 90 degree celcius coating is 25 amps yet the NEC dictates that a 14/2 NM-B cable must have an over current protection device rated at no more than 15amps. Obviously there is also a safety issue at work here but the fact remains that the industry standard for a 15 amp residential circuit is 14/2 NM-B. Would you suggest to an electrician to simply pop in a 20 amp breaker if the 15 amp breaker is only tripping occasionaly? Even though we all know that a 14awg cable can actually handle hundreds of amps without failure?

Low budget but high performance video splitters & amplifiers w/ adjustable gain try calrad electronics in Hollywood California. Talk to Wes the guy is a genius with troubleshooting and will have a product to help you.

Oh boy, gang...I didn't mean to ignite another debate on the subject. I was just explaining what I have to work with.

Let's not turn this thread into a flame-fest. If you want to debate CCS vs SC, please take it outside (i.e. start a new thread). In fact, that might not be a bad idea. Let's start a thread that includes DOCUMENTATION to support the viewpoint discussed.

...and guys...let's keep the namecalling to a minimum.

Thanks,

Fred

Actually, this is an interesting debate and well worth the digressions. Let's look at an analog. Recently on the Yahoo group one of the particpants pointed out that despite Crestron being a 24v network one could use a 12v power supply on the system and it would work. The system would certainly run "hotter" and this was not something one would want to do over the long term, but if one had no power supply and one needed to program in one's hotel one might wish to use that knowledge to his benefit.

Fred is a salesman. The fact that a salesman can walk and talk at the same time is one of the Lord's miracles, much like the Holy Trinity or 666 ( what's today's date, again?). Humor aside, I can see why he would be uninterested in these theoretical details. He has a real problem that he would like to solve ( though I would like to think that he has a technical staff for this ). But again, participation on these boards ought to bring with it some education as well.

I think we have a conflict based upon two ideas. Received wisdom of what ought to be done and technical knowledge that allows you, assuming you possess it, to skit around the received wisdom. Much like my 12v power supply running a Crestron system would be frowned upon by everyone, understanding that you could do it and what the ramifications of it might be ( how well a Crestron system deals with heat for example ) might allow you to get away with things once in a while. Similiarly, while pure cooper is certainly the better material than CCS for baseband video might there be circumstances where, depending on the cable and a particular set of cable specifications it might not matter? It seems to me that one can accept the received wisdom and carry on using the accepted medium. Or one can advance one's knowledge of cable design and engineering and possibly learn under what circumstances, and, in particular, which specifications to pay attention to, get away with using the "wrong" wire.

For years, some made a big deal about using 75 ohm BNCs with 75 ohm video cable. Only most BNCs used by most of us were 50 ohm. Until Extron put the results of their engineering tests on their web site this debate turned hot and heavy. Turned out not to matter a wit, in fact, and then theroy was adduced to justify the results -- different from the theroy that was adduced to suggest that terrible things would happen from the connector/wire impedance mismatch.

The fact is that most of us a plain ignorant. A few of us --no names to protect the guilty are beyond the pale. When some information is being presented in these debates it's an opportunity for all of us to learn.

While I can understand why Ted might have taken umbridge many technicians I have run into at recording studios have precious little technical education.

Alan

Where is Chu Gai when we need him?

CJ

PS- Alan, did you get my email?

I'll respond off line. It would have helped if you had identified yourself. I had no idea who you were from the address.

Alan

Couldn't have said it better myself!

To Ted Wetzel...

Wasn't trying to put down Studio Engineers. I've met some who truly knew their stuff. But I've met plenty that have a cookbook, and are unable to deviate from their recipe. To me, a chef can follow the receipe, and has the skills to do so well, but often deviates, because he knows and understands well beyond the knowledge a cook possesses.

I've met engineers that had a difficult time figuring out which end of the soldering iron to grab! But these individuals tend to come to wrong conclusions because their view of the problem is flawed. If you can follow their reasoning, which sometimes can be difficult for the non engineer, and show how their assumptions are flawed, they'll usually come around quickly.

So, try not to assume I'm wrong because I don't follow your cook book. It's entirely possible I understand the issues at a level you don't.

Oh, don't get me wrong, I agree this is worth the digression. It's just that I know that this debate has taken place before, and might be better served in it's own thread instead of my lil' ol' technical question.


Looks like I'm gonna have to grow my hair longer to cover that pesky mark behind my ear.....and for the record, I am both salesman AND installer (out of necessity, long story...)


I am VERY interested in the technical details. This is what allows me to "walk and talk at the same time". Unlike the typical sales guy, I prefer to be educated on the subject of my craft. Not only does it make me a better sales person, it helps me in properly estimating jobs so my installers (me, at the moment) have to actually do the job. I was simply making the point that I thought this debate would be of better service to the entire forum if it had it's own thread that was more in the limelight and not buried in this thread. Far be it from me to espouse on the talents of those who possess far greater knowledge when it comes to installation. Believe it or not, the reason I read this forum (as well as those at IP, and to a lesser extent, AVS) is to learn.

That having been said, please continue with the lesssons!

Your congenial walking and talking host,

Fred

Yes, I am resurecting this thread in hope that bcf1963 will share the relavent wire specifications. A link might do, say a particular Belden cable ( since their specification catologue is on line ) but an example of an CCS cable that would work as a baseband cable if X feet in length might be a useful educational enterprise for all. And will make Fred less despiesed by his installation crews as he will tell them to leave the RF wires in place rather than repull serial digital cables.

Alan

My choices for my first choice for a cable are as follows: (What I'd choose...)

For RG/6U runs of baseband video (Best choice for runs of over 100ft.)
Bundled Cable: 7710A
Single Cable: 1694A

For RG/59U runs of baseband video
Bundled Cable: 7787A
Single Cable: 1855A
Really Flexible Single Cable, Jumper Cables: 1505F

Most here agree that RG/59 is adequate for almost all average jobs for component video. It should work with only slight loss of picture at 100ft. I believe the 1855A (RG/59U) poses good specs:

23 AWG center conductor of copper - DC resistance of center conductor 2.01ohms / 100ft

Shield of 100% coverage aluminum foil, and tinned copper braid of 95% coverage - DC resistance of shield 0.76ohms / 100ft

Freq Response - 1st number is Freq in MHz, 2nd is dB loss / 100ft
1 0.39
10 1.2
100 3.33
540 7.70

Now, lets compare that to Belden 1189A, a RG/6U cable aimed a RF video distribution.

18 AWG center conductor of Copper Covered Steel - DC resistance of center conductor 2.8 ohms / 100ft.

Shield is Quad layer, 100% foil, 60% aluminum braid, 100% foil, 40% braid - DC resistance of shield 0.48 ohms / 100ft.

Freq Response
5 0.67
55 1.6
211 2.87
550 4.71

So, the differences are as follows.

The RG/59U solid copper shows total DC resistance of 2.77 ohms / 100ft.

The RG/6U Quad CCS shows total DC resistance of 3.28 ohms / 100ft.

That a difference of 0.51 ohms / 100ft. with the advantage to the solid copper RG/59U.

The dB loss at DC of the RG/59U over the RG/6U would be:

compute dB= 10 log ( P2/P1)

In this case, we have resistance, and the resistance at the far end of the cable is always terminated in 75 ohms, a fixed resistance. Note that power is V * I, and since the voltage changes very little for the two cases, we can assume the current is constant, which makes the math a bit easier. This essentially changes our equation to reduce the power terms to V2/V1.

V1 = 75/(75+2.77) for the RG/59U = 0.964
V2 = 75/(75+3.28) for the RG/6 Quad CCS = .958

dB loss of RG/6U Quad compared to RG/59U
dB = 10 log (0.958 / 0.964) = -.028dB

Note gents, that this amount of loss is incredibly small. So for DCR, a small advantage goes to RG/59U.

For frequency performance, note that Belden doesn't give us the same test frequencies for both cables. The RG/6U may be slightly more loss at low frequencies, but not by much more than about 0.25dB.

At higher frequencies the RG/6U Quad CCS shows almost a 3dB advantage at 550MHz.

I give the first choice to the RG/59 based on the fact that's it's DC performance is a bit better. When looking at a picture using the two cables, I've always been hard pressed to say one was better than the other. The difference I notice is NOT in the detail in the picture. This makes sense, as the detail is contained in the highest frequency response of the cable, and this is better in the RG/6. The difference I've seen has been in the color of the picture. With the RG/6 the color was very slightly more muted. I believe this is because the color information is at much lower frequencies on average in the picture, resulting in the RG/59 showing slightly better performance that the RG/6 quad CCS.

Note that if you look up the performance of the RG/6U copper cable I mention, that it will perform better at both DC and high frequencies than the RG/59, and should also show a difference. In my experience, I may be able to tell a difference at about 60ft, but it was very slight. I'll use RG/59 at 100 ft with no sleep lost.

Anyway, that's my analysis of why the RG/6 Quad CCS should be fine in most applications. I wouldn't use it as my first choice, but I wouldn't tear up drywall to remove it.

Note also that any slight color shift, would be cancelled out by a video calibration. So if you're really worried about using RG/6 in a situation where your hand is forced, get an ISF calibration!

Looking forward to your comments...