Combining Off Air HDTV and Cable

Discussion in 'Archived Threads 2001-2004' started by Todd_Burns, Mar 30, 2002.

  1. Todd_Burns

    Todd_Burns Auditioning

    Joined:
    Mar 29, 2002
    Messages:
    4
    Likes Received:
    0
    Is there a system that will combine both the cable signal and the HDTV Off-Air Antenna signal so that I don't have to switch from Antenna A to Antenna B?
     
  2. Steve Berger

    Steve Berger Supporting Actor

    Joined:
    Sep 8, 2001
    Messages:
    972
    Likes Received:
    3
    It can be done but how easy or hard depends on the details. If your HDTV signals are UHF and all your cable stations are below the over-the-air frequencies available then a simple U-V combiner will join the signals. You will need to remember that ,for instance, UHF channel 19 = catv channel 70 when selecting an over the air station. I don't have a frequency chart here but cable numbers and frequencies are not completely sequential.

    There are a lot of variables involved . The complete channel setup of your cable system including the location of premiun scrambled stations,OTA frequencies,input connections on STB (some have separate coax connectors for CATV and OTA), input connections on TV and probably a few things I'm forgetting right now.

    You can do a lot with inexpensive items (I've inserted my own channel 3 -removing CNBC- to deliver a DVD signal to bedrooms and garage;but almost every neighborhood is going to have different setup configuration possibilities.
     
  3. Todd_Burns

    Todd_Burns Auditioning

    Joined:
    Mar 29, 2002
    Messages:
    4
    Likes Received:
    0
    That sounds cool. Do you modulate the signal over 3? I thought that if you modulate channels that it replaces the rest of the signal, or do you just use the modulator to select a channel and the rest of your cable signal still works looping through it? Thanks for the reply.
     
  4. Steve Berger

    Steve Berger Supporting Actor

    Joined:
    Sep 8, 2001
    Messages:
    972
    Likes Received:
    3
    I use a cheap ($15) channel 3 modulator (mono A/V to ch 3) with a cheap ($15) channel adder/combiner (with built-in trap for existing ch 3) to substitute my VCR/DVD/other signals in place of CNBC (ch 3 on my cable).

    This is not a high quality signal, just a way of watching things in odd parts of the house. Higher quality mod/combiners are available. They offer other channel options, some with stereo encoders. $100-$250 for consumer models ; $200-$1500 for commercial (apartment building type) models.

    These all source composite and S-video with analog audio to RF; they're only going to distribute HDTV after it's converted to analog by the TV or set top box, something the new DVI interface could limit or stop.

    Equipment does exist to shift and add RF signals into the cable stream (how do you think cable adds your local stations into different spots retaining stereo encoding) but it's a fairly expensive option for most home setups.

    Maybe there will be cheaper models showing up as more broadcasters go HDTV. Cable could of course add them themselves (a systen in New Jersey supposedly did this unannounced, surprising local viewers when their sets sets jumped to the HDTV feed automatically): but they would have to give up their 4-1 (analog) and 12-1 (digital) compression schemes to do it since the digital stream can't be compressed any further. In fact, the 6 MHZ bandwidth of HDTV was chosen so that it would fit with existing distribution systems without any new equipment needed.Most cable companies opted for compression rather than true expansion when they started adding more stations.
     

Share This Page