HD cable box strange operation

[etutor]

Noticed I'm getting nice HD reception directly from cable modem. HD cable box is not part of the circuit except for power cord being plugged in (nothing attached to input or output connectors). If I unplug cable box power cord my Samsung HDTV loses signal. Strange....unless some kind of communication being sent via power cord....
See attached diagram.

[ddeerrff]

Your cable MODEM has an RF input and RF output connectors (F connectors)?  What model is it?  Mine has an RF in and ethernet out.

Is the HD box connected to the TV with an HDMI  or component cables?

What channels do you get on the TV, and in particular, which channel numbers are you seeing HD on?

What you are describing is really not possible.......

[LoadStar]

Noticed I'm getting nice HD reception directly from cable modem. HD cable box is not part of the circuit except for power cord being plugged in (nothing attached to input or output connectors). If I unplug cable box power cord my Samsung HDTV loses signal. Strange....unless some kind of communication being sent via power cord....
See attached diagram.

I too question the "modem" that has an RF in and out. What make/model of modem is it? Are you certain it's a cable modem (i.e. a device for receiving high-speed internet on your computer)?

Time Warner does supply a box called a "tuning adapter" that looks somewhat like a cable modem. These are only used for those with a third-party cablecard device, like a TiVo. They look like this:

Is this what your "modem" looks like? If so, that device is completely unnecessary to you, and I'm not sure why it would have been hooked up in the first place.

In any case, you indicate on your attachment that you are receiving "4-1, 6-1, 12-1, etc." These are clearly not coming from your cable box, as cable channels do not have hyphenated channel numbers. These are just the over-the-air channels that you can receive using an antenna, or possibly as what are called "clear QAM" channels provided as a courtesy by the cable company. Either way, they indicate that the cable box is not at all in use at this point.

I don't at all have an explanation as to why your reception on your TV goes away if you unplug the cable box, given that it isn't even a functional device in your current setup.  You are certain that the only device you are unplugging the power to is the cable box?

The short answer is: no, no communication happens over the power cable, at least in this case. Power cables strictly carry power. In your setup, you definitely would need a coaxial cable connection between the wall and the cable box. From the cable box to the television, you would need to run either component RCA cables or an HDMI cable, then you would need to select that input on your TV. You would then change channels using the cable box remote, not the TV remote.

The longer version is it sounds like you should get the Time Warner guy back out, because your entire setup is completely, totally, entirely setup incorrectly. You are paying for a cable box you aren't using. You might have to pay for a "truck roll," but it will be worth it to get everything setup properly.

[ArgMeMatey]

Please post photos of the equipment and, if possible, the cables between all equipment.  If things are as diagrammed, the only possibility would be that the "modem" could be receiving an authorization signal from the "cable box".  

As previously mentioned, HD locals are sent in clear QAM to every subscriber at Basic and above.

[etutor]

Yes, I agree the cable box is not connected properly and when I put it in it's proper configuration it works fine. I've just been a Tech for so long that things like this bug me. When something like a power cord from a disconnected cable box is uplugged from a power strip it caused the TV conected to the same power strip to lose it's signal.

The power strip seems to play a role in this. If I plug the cable box into another AC outlet in the room I get no signal.

It seems as though there is some kind of communication traveling from the cable box power cord through the power strip and through the power cord of the TV.

Or could the cable box be generating (or leaking) an RF signal that the TV picks up?

Anyway, I'll take some photos and get some model numbers when I get home tonight. Maybe I'll monitor the line with a scope to see if anything shows up.

Dave
KX9DK

[WPXE ION]

Have you tried a different power strip? It sounds like its shutting off all the outlets when you un-plug the cable box. Assuming the cable box is in the first plug on the power strip.

Do you have any way to test the outlets for power like with a meter or one of those outlet testers from the hardware store that light up and tell you if things are wired properly or not?

[Nels Harvey]

Just a thought from here:  Try putting a knot in one of the line cords, or put a ferrite filter over the line cord.  If the signals are really on the line cord, this probably will stop the feed.