Digital/HDTV Cabling

[Garage Junkie]

It could be. The impedance mismatch between the equipment and the cable would give rise to reflections in the transmission line. That in turn could EASILY garble phase-shift-keyed signals, such as are used in QAM-based CATV systems; which in turn would require retransmission of the data for the program guide (or other data) to finish loading. If you also experienced chronic pixellation on that one drop, this would further confirm the theory.

Yes, I am getting some pixilation- not bad, but noticeable. Any way to deal with this short of replacing the whole wire?

 

[2ManyProjects]

Yes, I am getting some pixilation- not bad, but noticeable.

On that one drop, and ONLY on that one drop? And both with and WITHOUT the distribution amp in the circuit? Assuming "Yes" to both of those questions, then...

Any way to deal with this short of replacing the whole wire?

That's the only really practical way to do it. However, if due to the physical constraints, that is simply not feasible, there is one semi-off-the-wall long-shot... You could try to "tune" the mismatched coax, using a "stub" of similar coax spliced in at a specific distance from one end. It's an old Ham trick for tuning antenna feeds for minimum SWR. But without the appropriate instrumentation to guide you, it becomes a real "shot in the dark" proposition. You can read more about the technique here:

http://personal.ee.surrey.ac.uk/Personal/D.Jefferies/stubs.html

Or simply Google "stub tuning".

 

[jeffmoss26]

Where did you get the amp? Typically the cable company will provide one if needed...they installed one at my house (outside) free of charge.

 

[Scott P]

If you are going to replace the wire (which I think you will have to do), they add in two Cat5e cables to each outlet. Then you can have phone and wired and ready to install at you main panel.

Our house was a new build in 2005 and we bought it as an inventory home. It came with coax and two Cat5e run into each room. They didn't punch down the network jacks, but it made installing a wired network quite easy. It's so much more reliable and faster than wireless.

 

[dave*99]

On that one drop, and ONLY on that one drop? And both with and WITHOUT the distribution amp in the circuit? Assuming "Yes" to both of those questions, then...



That's the only really practical way to do it. However, if due to the physical constraints, that is simply not feasible, there is one semi-off-the-wall long-shot... You could try to "tune" the mismatched coax, using a "stub" of similar coax spliced in at a specific distance from one end. It's an old Ham trick for tuning antenna feeds for minimum SWR. But without the appropriate instrumentation to guide you, it becomes a real "shot in the dark" proposition. You can read more about the technique here:

http://personal.ee.surrey.ac.uk/Personal/D.Jefferies/stubs.html

Or simply Google "stub tuning".

Stub tuning is a narrow band tuning technique. This is also mentioned in the link you supplied. A CATV system is a broadband system. Stub tuning is not an option on this system.

 

[Garage Junkie]

Where did you get the amp? Typically the cable company will provide one if needed...they installed one at my house (outside) free of charge.

Bought it online after doing a little research. I figure that if I call the cable company to come back and look it over, they will just tell me there is no way to run their signal over the RG62...

 

[Garage Junkie]

Or simply Google "stub tuning".

Thanks, but that is waaaaay beyond me...

 

[Garage Junkie]

If you are going to replace the wire (which I think you will have to do), they add in two Cat5e cables to each outlet. Then you can have phone and wired and ready to install at you main panel.

Our house was a new build in 2005 and we bought it as an inventory home. It came with coax and two Cat5e run into each room. They didn't punch down the network jacks, but it made installing a wired network quite easy. It's so much more reliable and faster than wireless.

Thanks Scott- that was kind of what I was thinking- if I'm going to pull wire anywhere, I should at least pull some Cat 5 with it- easy to do and not too costly!

 

[2ManyProjects]

Or simply Google "stub tuning".

Thanks, but that is waaaaay beyond me...

That's OK. As I said, it would be a real longshot anyway.

Besides, the FAR more likely source of that pixellation is your distribution amplifier. To troubleshoot this, first disconnect ALL other splitters/drops/etc. from the incoming feed, except perhaps for the one feeding the router. If necessary, spend fifty cents on a dual-female barrel-type F-connector adapter, to temporarily connect that one branch to the incoming feed. If that clears up the picture, the NEXT step is to put everything back essentially the way it was, except substitute the smallest (i.e., least number of outputs) high-quality passive splitter you can find in place of the amplifier. Install 75-ohm screw-on terminators on any unused splitter outputs (but you really don't want to HAVE any unused outputs, as each one represents a waste of signal strength). Odds are the picture will still be good, or at least better than with the amp in the circuit.

 

[justsam]

Many of the impairments being discussed in this thread apply to the older analog world. Having said that is it always a good idea to match impedance on equipment and cable, you bet!

In todays digital world what you will typically have as a result of mismatch is lower signal transfer. If you really wanted to match impedance, you would do it with balun coils however they to would introduce insertion loss.

I agree with Tom in post 17, give it a try with what you have in place, and go from there. Any rework should be with proper cable. Use RG6 unless you have an exceptionally long run, RG11 is more trouble that it is worth.