SnapStream Blog

How to create your own (analog) cable TV head-end

December 17 2009 by Rakesh


SnapStream’s TV search products are used by organizations that strategically value TV. And, as it turns out, a lot of these customers see benefits from modulating their own in-house cable TV line-up. For most people, modulating their own in-house cable TV makes it easier to distribute television within their organizations. We have a lot of customers who already have their own cable head-ends but we also come across a lot of customers who ask us, "How do I build my own cable head-end?"

This article is for those customers.

Why build my own cable head-end?

First of all, why would you want to build a cable head-end? Why not just take the regular cable signal from your cable provider and distribute that over RF around your organization? Well, for a lot of people “regular” cable (ie what you get without any kind of a receiver or set-top box) doesn’t include channels that are important to them. Regular cable might not include certain sports packages – like NFL Sunday Ticket or NBA League Pass on DirecTV – or other channels.

For example, say CSPAN is important to you. Well, here in Houston, TX, our local cable provider (Comcast) has been moving channels from the “analog” spectrum into the digital only spectrum and CSPAN has been one of the channels that’s been moved. So the only way to get CPSAN in Houston on Comcast is using a digital cable box (or a DTA – digital to analog – box). And if you want to distribute that channel around to various TVs in your office without a digital cable box at every TV, then you look at building your own regular cable head-end!

Another reason why you might want to modulate your own cable line-up is you might want to include non-TV channels on your cable line-up. For example, maybe you have a few security cameras that you want to modulate to certain channels on your cable system.

Does SnapStream’s TV Search appliances support custom channel line-ups?

In a word, yes. Just give us the details and we’ll setup a custom channel line-up for your organization that exactly matches how you have things setup. So the program guide will work 100% in the SnapStream software.

How do I build my own cable head-end?

So how do you create your own cable head-end? It’s surprisingly easy. Here’s a high-level overview of what your system will look like:

click to enlarge image

1. Your TV source is usually going to be either satellite (here in the US that means DirecTV or Dish) or digital cable. Depending on how many channels you’re modulating (‘n’ in the above diagram), you’ll need a corresponding number of receivers or set-top boxes from your provider. And if you’re using a satellite service like DirecTV, you’ll need a multi-port switch to drive all of those set-top boxes off of one satellite dish. A multi-port switch is a sort of splitter for satellite service.

2. Each set-top box is set to a particular channel on that TV source. Then that set-top box connects to it’s corresponding modulator via RCA video and audio cables. Generally speaking, analog modulators come in two varieties:

  • "Channelized" modulators – this kind of modulator is hard-wired to modulate the audio/video passed into them to a particular channel # (ie to a particular frequency of the RF spectrum). You can’t change the channel number that it outputs on-the-fly.
  • "Agile" modulators – with an Agile modulator, you can configure, on the fly, what channel you want it to output on. This provides more flexibility with the channels you can output on, but with some sacrifice of quality. Agile modulators are also more expensive (roughly twice as expensive) than "Channelized" modulators.

The typical recommendation, as I’ve heard it, is that most of your modulators can be “channelized” and then maybe you add a few “agile” modulators in case you need to modulate to some random channels later down the line.

3. And then each of the modulators connects to the combiner via RF and the combiner mashes all the channels together into one RF signal. There are two types of combiners – ones with amplifiers built-in (“active combiners”) and ones without amplifiers (“passive combiners”). Depending on how you’re distributing RF (the next step), an “active” combiner might save you the need for a dedicated RF amplifier on the output of the combiner.

4. Last but not least, you need to distribute your new cable signal throughout your organization. Designing an RF distribution system is a separate topic unto itself (discussion of splitters and taps, signal loss of distance, etc.), but for simple configurations, you just need to amplify the signal at the exit to the combiner. How much you need to amplify it depends on how many ways you’re splitting it and how long the distances are in your RF network.

If you’re doing all of this so you can record TV and search over it with SnapStream, your SnapStream Server is 100% compatible with your new custom cable line-up. We have the ability to create custom line-ups so your program guide in SnapStream exactly matches how you have your channels configured.

Ballpark Pricing

You’ll need to contact a vendor or distributor of this equipment, but our quick calculations had the per channel cost of the modulators and combiners (EXCLUDING the cost of any multi-port switch, receivers, and RF distribution stuff), if you’re using “channelized” (ie “fixed”) modulators, come out to $150 / channel. And if you’re going with “agile” modulators, then the cost might go up to something like $250 / channel. Now this is just eyeball pricing.


That's it... Thanks to my friends at Blonder Tongue for their help in putting this together. And if you're reading this and want to be able to record LOTS of TV and then search inside those TV shows, let us know. That's what our product, SnapStream, is all about!

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