Adding a slingbox channel to my existing coax (with basic cable service)

A modulator will only work with SD signals, not with HD. Do you plan on sending any HD?

You can use a low-pass-filter on your incoming coax feed to block all frequencies above a certain channel (LPF-450 will block everything above cable 62 for example) and combine your modulated channel(s) above that with a simple splitter wired in reverse.

The LPF will also serve to block the neighbor's access to your in-house channel. They're $40 new, but I just got one (an LPF-650) on Ebay for less than half of that.

To your first question: yes, it blocks in both directions, so it will work like you want.

To your second question: be aware (it sounds like you might already be) that what your cable box "says" is digital channel 118 might not be channel 118 in terms of frequencies. If you know that the carrier is on channel 118 (your cable box diagnostics or tuner card might call it "118.1" "118.2", etc) then it will be partially attenuated by the filter (and 120 will be worse than 119, worse than 118, etc). My gut feeling is that 117 might work and 118 and above probably wouldn't, but it's so situationally dependent that it's impossible to say. (What signal strength your cable co is putting out, the cabling in your house, the sensitivity of the tuner you're using, etc.)

LPF will definitely isolate your house channel to your house.

You can inject the house channel anywhere in your house, but it will only be usably viewable to the entire house if you do it before the splitter(s). I have all my equipment centrally located, filter the incoming coax and inject my house channels there and only once all that's done, run it through a powered splitter to feed the house. I'm pretty sure you couldn't inject at the family room TV and expect to see that channel (at a usable signal level) on a bedroom TV.

As for your 118 question, if you have a agile modulator, just set it to 118, combine it onto your cable feed and see if the digital cable channels you suspect are on 118 are still clear. If they are, they aren't on 118.

Can someone break down what was described above into utter lamen terms?

I'm wanting to do basically the same thing... add a composite channel to all the tvs in my house... so each tv could go to channel 80 (or whatever) and see what was on that dvd player. I have access to my cable source (before it gets split) and i have the 3 rca cables from the dvd player...

There are three parts I wasn't quite clear on:

1) What type of unit do I need to buy that would add the composite channel to the coax without messing up what's already coming in on the coax? This is the big question... I can't figure out what to search for or how much I should expect to pay.

2) I also receive internet and digital cable through the coax... is there a way to do this without messing up those things?

3) What's the purpose of the low pass filter and what specs would I need if I were buying one?

Thanks!

1. Modulator will take the "red/white/yellow" composite video and audio and turn it into a cable channel. You specifically want a "frequency agile" modulator (that means "you can pick the channel it uses"). Channel Plus makes a whole line of them; I use the 5545 and SVM-24. Each can do 4 channels and do IR control. There's a 5525 that does 2, and many other models to choose from.

Then, you need a device to combine two coax feeds, one from that unit and one from the cable company. I use the Channel Plus 8200 for that, which also provides power to the IR targets and relays the IR commands back to the modulator.

At each TV, I have 2133 targets (to hit with the remote controls for the DVD player in your case). The signal comes from the remote and hits the 2133. That puts it on the coax and sends it back to the 8200, which sends it to the modulator, which has IR emitters attached to control the DVD player.

Channel plus sells this all in a kit, the numbers of which I'm a little too time-pressed to look up, but some quick googling on your part should turn it up.

2. As long as you stick to high channels, you won't interfere with the cable modem, though you'll need to get the 8200-BID (bi-directional) to support a cable modem. Instead, I moved my cable modem to the basement cable entry and it's before all the video stuff.

Digital cable will cause a conflict if you pick the same channel that the cable company is using for their digital signal. (Note that the channels you see on the cable box, 852, 354, etc, aren't the actual channels on the coax; they're just a convenience for you.)

3. THe low pass filter is to block all the channels on the cable company feed to "clear out" some channels for you to use in the house. I knock out channels 69 and above (something approximately like that anyway), and I use the high number channels for my house channels. That does mean that a digital cable box won't work in the main part of my house, so if I had one, I'd have to put it in the basement and treat it like you're going to use the DVD player. (Put its output on a house channel, and cable its coax feed up before the low-pass filter.) That would also preclude getting many HD channels in HD, as the modulation is entirely SD NTSC.

If your cable company isn't using channel 79, 80 or 81 for their signal, you probably won't need the LPF and you can just get channel 80 overlaid onto your feed no problem. If they are, you'll need to find a spot where there's 3 channels in a row not in use, or you'll need to use filters.

Fantastic response. Thanks so much for your help... I'll give it a shot.

Adding a question to this really good discussion.

If I want the signal being bounced around the house from a single source to be HD quality, is there specific type of equipment I should buy? Is it even possible to "forward" a 1080p signal (or any high def for that matter) using this method?

By "bounced around" do you mean wirelessly or wired?

There are "soon to be released" options for wireless and available options for wired.

I mean wired. I have no issues running wires, I just want to make sure that I get a good 1080 signal to every tv that is sharing the signal.

Referring to modulators, I'm not aware of any ATSC/QAM modulators on the market. There's been some announcements, but they've all been vaporware so far. If anyone knows of any actual hardware, I think we'd all like to hear about it.

On a side note, does anyone have any experience using a channel modulator with Fios? I'll be moving to a Fios area soon, and I'm not sure about my options here.

would something like this work?

http://www.atvresearch.com/dsp806pic...processor.aspx

A few things here:

1) There is a QAM modulator currently on the market from a company called Zeevee.com - they run about $1000 for a single channel, are frequency agile, and must be filtered/combined like any "off the shelf modulator" - Other options are coming but this is the only "reasonably priced one" currently on the market.

2) As for modulation, there is a lot of info on this post, but the biggest recurring issue is loss of (either through interference or filtering out) valuable CATV channels. Unless a household is PURELY analog (meaning no set top boxes of any kind, no cable modem, no VOIP, and no reception of digital channels with a digital tuner built into a TV) then any standard way to filter out channels and insert your own will will result in loss of something. (That includes channel notch filters, low pass filtering etc.)

So far, the only way folks have avoided that loss has been to use frequencies around 100Mhz (specifically because that is where FM stations are located and most cable companies tend to avoid using those frequencies) - BUT the problem is that off the shelf modulators cannot use those frequencies due to sidebands they create. They end up knocking out 20 or 30 channels if you force them to those frequencies. (If you are really interested feel free to look at this little presentation)

Before you read on, a little caveat, I am associated with the company that makes the following product and am therefore biased - so research it for yourself (see the BOCS thread in this same forum)...

The BOCS product can take up to three inputs and distribute them home-wide using the FM band AND can both transmit and receive on the same coax wire (no need to put the modulator at the demarc point - put it anywhere in the home even with a single wire), it does not interfere with analog or digital cable, AND it includes the full wireless remote control system spoken of above. It also includes all the filtering so your neighbors cannot see the stream. The nice extra is that beyond a sling or security camera you can plug two other things in - the most common is a DVR - watch those recorded shows from anywhere else in the home. Lots more detailed info on the website www.bocsco.com

David Feller

Sorry, I missed responding to this - the reason you are having trouble is that whatever channel you put your modulator on - even if you tune your TV to that same channel to see if anything is there - is occupied by either analog or digital signals. You MUST filter. Low pass are the easiest but obviously known out the most. There are lots available and you can get them from solidsignal and many other places online.

David