Combining CCTV and TV on the same RG6 cable?

[slice1900 0]

I want to install CCTV in my business, where I currently have RG6 cable run to TVs near to the locations where I'd like the cameras. Due to the building construction, either running additional cabling or using wireless would be very problematic. Therefore I'm hoping there is some way I could use a diplexer or similar solution to run both signals over the same cable.

 

There are 5 locations I want to run CCTV to using simple fixed dome cameras, so I'm planning on buying a system with a DVR that can handle 8 cameras to leave room for possible expansion. The cabling from the TVs is run from a secure central location where I would locate the DVR. I was hoping there was some way of sending out the signal (broadcast, not satellite) to the TVs and using the same cable to carry the CCTV analog video back to the DVR.

 

Power is available at the camera locations, so if I can share the coax for TV and CCTV but not power that's not a problem. I just want to know whether there's any way the video signal for the CCTV cameras can be sent back to the DVR over the same cable without interfering with the TV signal. And doesn't cost so much that drilling through concrete to run new cables becomes the cheap option!

[the toss 0]

I've no doubt that it s possible but not having ever done I cannot advise on gear or cost. Since your TV signal is RF (100s of MHz) and your camera is baseband ( <6Mhz ) transporting them on the same cable should present no technical problems.

[bigglebowski 0]

If you are in the US this can be done with "T-Channel" modulators and demodulators that can tune the sub band T channels. Since this equipment is atypical as opposed regular channel modulators like Ch2-135. To get this done properly would probably be more expensive than hiring somebody to pull the wire even if wire mold had to be used.

 

It could be possible to do with regular channel modulators as long as those frequencies were not being used, but balancing this and filtering it could be messy.

[bigglebowski 0]

I've no doubt that it s possible but not having ever done I cannot advise on gear or cost. Since your TV signal is RF (100s of MHz) and your camera is baseband ( <6Mhz ) transporting them on the same cable should present no technical problems.

 

You would end up with excessive noise on both feeds TV and the composite video. Besides even if one camera feed worked you couldnt do the next 4 cameras.

[slice1900 0]

A diplexer is essentially a splitter/coupler with a high pass filter on one leg and a low pass filter on the other, right? While they make them for satellite to separate signals above and below 900 MHz, I need one that separates signals somewhere in the range of 6 MHz to 50 MHz, between the top of the baseband composite video feed and the bottom of the TV band. So I was thinking of something like this in the closet where all the cables return:

 

Each cable coming out of the splitter going to the TVs that I want to also run CCTV on I'd attach a low pass filter to screen out the CCTV signal. To that I'd attach a splitter/coupler, and one leg would go towards the DVR, with a high pass filter on it to block out the TV signal. On the other leg I'd have the run out to the TV, unfiltered since it would carry both signals.

 

At each TV I'd have another splitter/coupler connected to that cable, unfiltered on that connection. Then add a low pass filter on the leg going to the TV and a high pass filter on the leg going to the CCTV camera.

 

Assuming I can find RG6 couplers that act as low pass or high pass filters like I'm suggesting, is there any reason this wouldn't work? Or would I still see excessive noise? If so, what would be the source of the noise, and is there anything else I could do to get rid of it?

[bigglebowski 0]

Diplexers work when combining 2 different blocks of frequencies that already do not conflict with each other. For example "legacy" satellite signal was 950-1450 Mhz. 10+ years ago cable TV freqeuncies were basically 5-900 Mhz (today depending on the cable system it could go well into GHZ, and sat +2Ghz). So you could use a diplexer with a 950-1450 Mhz port and a 5-900 Mhz port and share the same cable, and even pass voltage over that cable only passing on the satellite side. Thats why I mentioned using a device that actively converts/unconverts at both ends of the coax.

 

Composite video doesnt really have a set frequency so it will end up interfering with the TV channels and the TV channels will interfere with the camera video. Could also really interfere with signals that travel back to the cable system (T channels) like cable modem upload or set top box communication. That is what I meant by noise.

 

One other thing I can think of that will enable you to share the cable would be to look into MOCA but it means you will need to go IP based cameras. These devices will give you Ethernet over your coax which should operate above the frequencies that the cable company uses. With MOCA you would have one moca device where your splitters for the cable feed are, so you will need an open splitter port to hook it up to your router. Then you would have a splitter at the end of each cable run (one port=TV, other=MOCA). You may find you need to use higher than typical frequency splitters which would be ones designed for satellite (like directv SWM splitters). I think the moca frequencies go up to 1500 Mhz, but most satellite splitters go up to 2500 Mhz. If needed you could use POE injectors after the MOCA to feed camera power.

 

Edit: Noticed that some MOCA devices come with a loop through cable connection so splitters may not be needed.

[slice1900 0]

As I understand it, composite video is a video signal using standard analog encoding (NTSC, PAL, whatever one's local standard is) that starts at 0 MHz and goes up to the bandwidth of the signal. So the highest frequency would be around 6 Mhz. Higher if you are doing HD resolutions, though I believe most HD CCTV cameras are IP. As you say, the bottom of the cable TV subchannels is around that range (5.5 Mhz) so it would present a real problem.

 

Fortunately in my case I'm not using cable TV but over the air broadcast TV, so there is only one way communication, and the lowest frequency should be 50 MHz or so, well above the maximum frequency of the composite video signal. I think what I'm looking to do may still be possible, but you did point out something I hadn't thought of. I'll have to be aware that if I am able to make this solution work I'd never be able to switch to cable TV. Not a problem for me, but it may explain why I wasn't able to google anyone doing this, as it would be a show stopper for anyone using cable TV, or planning to in the future.

 

I have heard of MOCA but hadn't considered it here. I don't want to do IP cameras if I don't have to since they're more expensive, and MOCA doesn't appear to be cheap either, but if I can't make this work then MOCA would be a good alternative. Cheaper than running new wiring, that's for sure. Thanks for the suggestion, that will make a good backup plan!

[bigglebowski 0]

Lets assume you can just use a 2 way splitter and put the 1st camera on there well how do you get 2-5 on there? You have to convert each to a unique frequency to put them on the same cable.

 

If you are using off air TV then you will have more options since at best there will be approx 15 broadcast channels within range and is on your MATV system.. You could use "cable" frequency modulators like ch14-60 and should avoid either VHF or UHF broadcasts in your area. However this would NOT work with any cable TV system that use the same channels as your modulators. You should be able to utilize simple splitters or even cable TV taps to achieve this. Then you would have a demodulator per modulator at the source location to convert the signals back to composite video.

 

To pull it off well it would really help if you had a signal meter capable of reading the various frequencies that are on the cable so that you can balance the signal levels of your modulated channels vs. the over the air channels that are on the line. Plus the issue of balancing digital vs analog signals.

 

Even with a high bandwidth cable TV system there are ways to keep a system like this sharing the same cable but would require very expensive and most likely custom trap filters. This is not uncommon but again these are parts that will put you into the budget of just going ahead and doing it IP.

[slice1900 0]

I must have been unclear in my initial posting. I have a splitter in the closet connected to the roof antenna on the input, with a separate cable going to each TV on the output. Each camera would be located near a different TV, so only one camera per cable. I don't need to worry about having multiple cameras on a single cable, that would indeed be a nightmare and I wouldn't even contemplate doing something like that. As you say, at that point the expense of an all IP system and MOCA probably becomes smaller and the headaches far less.

 

I think most of the difficulty for me making this work is in the closet. If I can get that end working, I can use the same solutions to overcome any problems I run into on the TV end. It may turn out that simply connecting a splitter on the TV end will work, and the camera won't care that a TV signal at 50+ MHz is being sent into it since its not a receiver, and the TV won't care that a composite signal below 6 MHz is being sent into it because it is tuning to a TV signal on a much higher frequency. But like I said, any problems on this end would be simple to solve if I can get the other end nailed down.

 

In the closet I'll need to couple the TV signal from the antenna with the composite signal from the camera so they can share the cable between the closet and the TV location. For this I need a two way splitter with the input connected to the cable that goes to the TV, one output connected to the output of the big splitter and the other output connected to the DVR. If as I suspect the DVR doesn't care about the TV signal at 50 MHz and above then that half of it is solved. I think the key to making this work is figuring out what to do with the cable that runs from the output of the two way splitter to the output of the big splitter.

 

The problem here as I see it is that I can't leave the composite signal on that cable when it enters the big splitter - it would interfere with the composite signal from the other cables within that splitter and the DVR would receive nothing but gibberish from all five cameras. So I need to block the composite signal in some way. I came up with three ideas for this, but only one looks feasible right now:

 

1) replace my big splitter with a "one way splitter". If such a thing existed, that would be great, but I couldn't find any evidence of one in a few minutes of googling so I'm pretty sure it doesn't

 

2) replace the two way splitter with a diplexer, one that works on a frequency somewhere in the 10 - 50 MHz range instead of the 900 MHz range of the common satellite diplexers. I didn't have any luck finding this. There is probably not much demand for that particular part, so it is probably only available cost effectively if you were able to order many thousands at once.

 

3) add a low pass filter that filters out the composite video between the two way splitter and the big splitter. I found these, available as an F type connector I could easily inline on my coax, for $30 US. If I only need 5, that would be great. If I ended up needing 5 more on the other end and/or need some high pass filters as well (which are also available at the same price) then it might start getting pricier.

[bigglebowski 0]

Ok so ignoring the potential problems of conflicts with both signals on the same wire. The splitter/diplexer itself will be a problem as well. I bet that with short cables and just one splitter in the line will be enough to ruin your composite video signal. If you have a camera or a DVD that has composite video output try hooking it up to a TV splitter (will need BNC and RCA to F adapters) and I bet you will find it ruins your signal. Then keep in mind you will end up needing another splitter on that line and depending on how long your cable TV lines are your image will be terrible without even hooking TV to it. You may also find that 2 splitters in the line may reduce your UHF signal to the point where the weaker channels will drop out. This can be corrected with an amplifier though, but then you could over amplify the stronger signals.

 

Another issue is if your lines are long distance TV coax just does not perform as well as video grade coax. Video grade coax will have an all copper center conductor and copper braiding. TV coax will usually have copper clad steel center conductors and steel braiding. Newer cable used by Dish/Directv installers will have copper center conductor because of the higher voltage and current needed by modern LNBs on dishes.

 

Maybe another cheap solution may be to just use the coax for your cameras and try hooking up local antennas on the back of your TVs.

 

What kind of cameras were you going to use? Do you have one already to at least try with your longest coax to see if the image is OK?

[slice1900 0]

I am planning on using the composite output of an old VCR to help with a small scale test of what I'm looking at. I'm going to buy one of those $30 low pass filters and try out the scheme I outlined above. If I run into problems then I'll have to see if I can figure out if additional filters might be needed to fix things.

 

If I run into signal strength problems like you suggest then there won't be much I can do about it aside from going to an IP/MOCA solution. I'll make sure my testing includes sending the composite signal through my longest run with a couple splitters in the path to verify I don't have the signal strength problems you're suggesting. That is something I definitely need to make sure I try since low/high pass filters won't fix that type of issue.

 

I'm not sure what type of coax I have. I don't know how to tell the difference between RG6 and RG59 since the connectors are identical? The little wire that comes out of the connector is copper coloured but I have no idea if it is copper all the way through or just coated.

 

I don't have any cameras yet, I wanted to first determine if sharing the coax with a composite image would work before I purchased, in case I needed to use IP cameras. Hopefully the composite signal the cameras output is similar in strength to the composite signal a VCR outputs, but when purchasing I'll make sure I can return the cameras if I run into trouble and need to fall back to the IP/MOCA solution.

 

Thank you for everything you've brought up as potential problems! Since I didn't get any feedback either way from people who have actually tried this I still have no idea of whether it is truly doable or not. It is good to have someone bring up as many potential issues as possible to test before I decide on the camera/DVR package.

[bigglebowski 0]

Just start with the splitters first before buying anything. I think you will find that the video going through just one splitter will not be acceptable to you. Unless you have them for some reason buy get a pair of RCA to F adapters to hook up the cables.

 

Simple way to tell if your coax has a steel core would be a magnet. Solid copper conductor is just not needed for RF signals since they only travel down the skin of the conductor which is where the copper clad is. With DC for powering LNBs and video which is basically a DC signal it occupies the whole conductor. That is why running video over TV grade coax at long distance is not ideal.

 

RG6 has a thicker center conductor of 18 awg and RG59 is 20 awg.