Instead of buying another TiVo, ReplayTV or sitting in front of your PC to watch your recorded movies, consider implementing a whole house coax based network that allows you to watch AND control those devices from any TV in any room attached to the network. Using off-the-shelf technology you can send your AV signals from any source to all your TVs on standard Coax Cable. We introduce you to the basics of Coax technology and how you can broadcast your PC or PVR movies to all your TVs.

Broadcast your Video/Audio Sources to your TVs

Scott Clark | Crossbar Media

Broadcast your Video/Audio Sources to your TVs
By Scott Clark, Crossbar Media

Instead of buying another TiVo, ReplayTV or sitting in front of your PC to watch your recorded movies, consider implementing a whole house coax based network that allows you to watch AND control those devices from any TV in any room attached to the network. Using off-the-shelf technology you can send your AV signals from any source to all your TVs on standard Coax Cable. We introduce you to the basics of Coax technology and how you can broadcast your PC or PVR movies to all your TVs.


Do you have a PC with a TV tuner and/or a DVD player and have some of your movies on your PC in various formats; MPEG, DIVX, AVI, WMV, etc…? Do you want to watch them on your PC only or do you sometimes want to watch them in your den or bedroom (without moving your PC to the TV room)? Do you have a security camera and don't want to buy or dedicate a TV/monitor to view its transmission? Do you have a TiVo or ReplayTV and want to watch your movies on all your TVs? If you answered yes to these questions, this article is for you.

There are two basic approaches to implement a solution to this situation; a wired solution and a wireless solution. Which solution you choose will depend on several factors such as how many TVs you have, how many devices you ultimately want to have on your network, existing cables/systems you have or don't have, cost, quality, etc… The focus of this article is to show you how to implement a wired solution that allows you to view, control and add new sources of Video/Audio, add additional TVs without impact on performance and quality.

Your Cable Network

A typical cable TV network in your home usually starts out with a feed from your Cable Company or your Satellite Dish. The feed then is split using a splitter with various outputs being sent to AV units such as Set Top Boxes, Cable Modems, TVs or other splitters. Each time a splitter is introduced in the network original signal degrades or attenuates by some amount. The attenuation is noticeable when an inexpensive splitter is used or when enough splitters and T-connectors are introduced into the network.

Professional installers of Video/Audio cable network will typically use a high quality passive splitter on a small network and use a high quality active splitter if there are many cable drops or long cable runs.

The Active Amplifier

Active amplifiers and splitters will amplify outgoing signals while minimizing the introduction of noise into the network. Since most people do not transmit their own signals onto the cable network, most amplifiers do not block reverse transmission back into the network (or neighbors) from your home. If you are going to broadcast to your home network, you will need to make sure that you are also not broadcasting to your neighbors on the channels of choice. The Avcast CableCaster is such a unit.

The Notch Filter

Most cable network channels are already crowded and it is unlikely to find some clear channels to send your signals over. A device called the Notch Filter will block or clear certain channel ranges so that you can transmit your personal channels over the blocked channels. In this manner, the broadcast signal will be clean and crisp. Notch filters can block channels in ranges (sometimes in units of five, others in units of 15 or more) such as 65-70 on your CATV channel range.

The single source AV

The simplest way to connect any AV Source to your cable network is to output your signal from your source to a modulator and attach the modulator to the cable network. A modulator takes the Video and Audio signal from your source and modulates the signal onto the selected channel to be transmitted on the cable network. Some modulators, like the one built into your VCR, can only modulate signals on channels 3 and 4 while others are capable of modulating signals over a much wider range of channels.

The signal coming into the network can now be sent out using a passive splitter or an active amplifier-splitter. If using a CableCaster, the signal gets reflected on existing cables. However, if using another kind of splitter, it needs to be fed into the input and combined with other signals from the cable company. A regular splitter will let it cross the port-to-port isolation, but the signal will be weakened, and the signal will get out to the neighbors.

As you will quickly note, you can connect any source of Video and Audio to this network. Your source can be a PVR (such as TiVo, ReplayTV), a PC, DVD or a security camera.

Watching your PC movies from any TV

It is very common today to have a DVD and/or a TV Tuner in your PC. You are able to save your recordings on your hard drives for later viewing in just about any format such as MPEG, AVI, WMV or DIVX. But having hundreds of hours of movies on your large disk and sitting in front of your monitor to watch them is not a good thing. And you don't have to! You can watch your movies from any TV on your cable network. Here's what you need:

  • A Video Card with a TV-out capability. First you need to be happy with the signal your video card sends out to the TV through the TV-Out port. In order to see if this is acceptable, hook up a TV to the TV-Out port; usually the TV-out is an S-Video connector so you will need an S-Video to RCA cable adapter if your TV doesn't have an S-Video input. At this point you will need to go to your control panel and make sure that your Video card is enabled to send the TV-out signal. This method will vary depending on the video card manufacturer. If you're happy with the quality of the signal, then the signal that will be modulated will be acceptable.
  • You will also need to get an S-Video to RCA cable and an Audio Y cable that splits the audio out from the sound card to a Right and Left channel output. You will also need an RCA AV cable
  • Now connect your PC Video out and Audio out to the corresponding inputs of the modulator. Select the channel you want to broadcast your signal on the modulator - That is it. Now, whenever you play a movie on your PC and your TV-out is enabled, what you would see on your computer monitor will be shown on your TV. If you have an RF remote control device (such as an RF keyboard or mouse) you can even control your PC remotely.

An Uber Network?

You can implement this kind of network today with off-the-shelf technology. If running wires in your house is something you can easily accomplish then consider this diagram below with separate runs to the Cable Modem and to the Cable Set Top Box. Of course, what you connect to the networks will depend on what devices you have in your home and what you think is worth sharing with all your TVs.

The diagram below is basically the same one as above, with a few extra TVs, but we've eliminated the separate wire runs and made all devices connect through the CableCaster "backplane". The introduction of the DOCSIS Reverse Channel Amplifier allows us to transmit Cable TV and Modem signals back to the Cable Company without any problems. You will note that in this case, the DOCSIS compatible line amplifier sits directly on the network ports of the CableCaster and does not connect to the incoming port of the CableCaster. That port is left unused.

Things you need to know about Coaxial Cable Networks

The type of coaxial cable installed in a house and the method used to connect the cables both influence the quality of the pictures that you view on the devices in the home entertainment network. There are two types of coaxial cable used in homes today: RG-59 and RG-6.

  • RG-59 coaxial cable has been used for wiring Cable TV into homes since the 1970s, and has only recently been replaced by the superior RG-6 cable. RG-59 has a very large amount of signal loss for the higher frequencies. This means that for longer cable runs, CATV stations above channel 65 will be weak and may have snow and other distortion.
  • RG-6 coaxial cable has a much lower frequency loss than has RG-59 cable. RG-6 cable has twice the bandwidth of the old RG-59 cable, providing a clear picture up to channel 158.
  • When buying cable, remember that all coaxial cable is not created equal. There are many different types of RG-6 cable. Any RG-6 cable that you get should be shielded with both a braid and aluminum foil wrap. The following table for example shows the signal loss per 100ft and 100meters for both RG59 and RG-6 Coax at the 1000 MHz range.

Frequency vs. Signal Loss for RG-59 and RG-6 Coaxial Cable

 

RG-59 Coax

RG-6 Coax

MHz

Closest
Cable Ch.

Closest
UHF Ch.

Loss/100 ft

Loss/100 m

Loss/100 ft

Loss/100 m

1000

158

N/A

10.9 dBmV

35.8 dBmV

7.3 dBmV

23.9 dBmV

Assuming a perfect input of 15.0 dBmV and a 1000MHz signal, a 100-foot RG-59 coaxial cable loses about 75% of its original signal at high frequencies, while a similar RG-6 cable loses about 50%.

Cable Signal Loss Considerations

If you want to have the best possible pictures delivered by your distribution system, you will need to determine the signal losses that will occur through your cable system. Signal strength decreases with coaxial cable length, and through connectors, splitters and combiners. You will need to determine how much cable and what in-line devices you'll be using.

Ideally, to produce a crisp sharp picture, each TV should have a signal level between 8 and 15 dBmV. The cable company is required by the FCC to deliver to each TV set a 0 dBmV signal (no snow is visible). If you see snow on the screen your signal level is about -10dBmV (snowy picture).

The FCC allows a maximum of 15.5 dBmV to a TV set because older TV sets without automatic gain control will be over-driven (waves appear on the picture) with a stronger signal. Most TV sets made in the last 10 years can accept a signal as high as 40 dBmV.

If you have a TV set without automatic gain control and you see waves going through the picture, an in-line attenuator can be used to reduce the signal strength. In-line attenuators are sold at stores such as Radio Shack.

Summary

Instead of buying another TiVo or ReplayTV or sitting in front of your PC to watch your recorded movies, consider implementing a whole house coax based network that allows you to watch AND control those devices from any TV in any room attached to the network. Using off-the-shelf technology you can send your AV signals from any source to all your TVs on standard Coax Cable. We introduced you to the basics of Coax technology and how you can broadcast your PC or PVR movies to all your TVs.


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