Digital Cable with Video feed

[buitenhek]

I have digital cable routed throughout the house and wanted to install an outside camera that would show who was at the front door from any TV that was on in the house via picture-in-picture. I used a ChannelVision multiplexer to mix the video (open channel #83) with the digital cable signal.

It works marginally but several digital channels frame insistently. The Roadrunner people don’t want to hear about the mux and insist the signal is good enough (without the video feed installed) at the TV furthest away that they are washing there hands of this problem. It is true that without the feed the signal is OK.

Can anyone suggest a course of action?

Peter


Regards
Peter Buitenhek
Profit Developer.com

 

[daronwilson]

I ran into this as well. I had a rather low end triple input modulator, and it was sloppy and very wide, thus taking out 6-8 channels. I ended up ditching it and getting a Channel Plus frequency agile modulator and finding a channel that had an empty (guard) channel on either side of it. It seems that these modulators are all pretty wide and not really narrowed to the 6Mhz that they should be for one channel. With the Channel Plus single input modulator, I put an external camera on a channel that had nothing adjacent to it, and it still caused a bit of trouble. We ended up adding a band pass filter on the channel, and reject filters on the two adjacent channels and it came up beautifully.

If possible you need to find out from the cable company which channels they are not using, or alternatively scroll through them with a CATV meter and check for unused channels.

I would definately stick with something frequency agile, because the cable company has the tendancy to jump around a bit with their services.

Good Luck!

It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com

 

[Servamatic]

Daron is correct.
Anytime you modulate you need a free channel on both sides of the one you want the picture on.
You can also get a low pass filter from Channel Plus or Leviton (the ones I have used) that can wipe a series of channels out for use with a modulator.

Try this link as a starting point for LPF's

http://www.multiplextechnology.com/channelplus/products/rf.html#accessoriesrf

They list several, and ChannelPlus has a pretty good technical library.

Richard S. Anderson, RCDD

http://www.smartbuilthomes.com

 

[AvayaNovice]

Depending on what their headend equipment is (ie. motorola or scientific atlanta), channel 83 is a little too close to channel 80. Digital boxes using channel 80 for anything that's not analog cable. In most areas, channels 1-100 are going to be analog (Even though you have a digital box) and the channels above that will be digital. All of those "digital" channels come in over channel 80. The lightest bit of interference can cause that framing, as it has trouble syncing.

A good way to tell, depending on what brand of box you have, is to use its internal meter.

On scientific atlanta boxes, that means holding down the center select button that's inbetween the arrow buttons on the box itself, until the message light blinks. Then hit the info button, or in the case of an older box, the diamond button. This will bring up the diagonistic screen, and you can check out both forward and reverse path from there.

Another thing to note, is that modulators can cause significt issues with the return signal. A good return meter can tell you what's going on there (trilithics are great, and cheap). A return level out of the 35-60 scope will cause major problems with snyc and any reverse path services (ie. pay per view, etc.)

If I were you, I'd be shooting for a channel that's no where near 80, most cable providers won't use any of the higher band channels (ie. above 100, although only some boxes can tune to that) or better yet, something just below 100. We rarely use those channels for actual services due to their high roll off with RG-59, and even moreso, line loss.