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Thread: Multiroom via frequency agile RF modulator

  1. #1
    Join Date
    Feb 2003
    Posts
    155

    Multiroom via frequency agile RF modulator

    I distribute my Tivo's to all TV's in our house using RF.
    Terk Remote extenders relay IR to the basement where the Tivos live. I use a notch filter to wack out cable above channel 70, and insert my Tivo's RF there. Every room has a URC6131 JP1ed to control multiple Tivos and the AV gear relevant to that room. Bottom line is every room can watch cable or any Tivo with only one remote per room. Although RF modulation is not the "best", it avoids deploying an Xbox at every set, uses existing coax wiring, and provides a clean uniform "UI" for controlling the gear in any room.

    The "main" set uses optical audio/svideo for best quality. Some TV's in the house are Stereo and most modulator's are mono. Stereo modulators cost a fortune (~$500-$1000). Radio Shack sells a frequency agile "mono" modulator that can output on any channel for about $30. They also sell a "channel 3/4" modulator that is stereo for about $30. My hardware hack allows these 2 modulators to work together to produce stereo RF on any channel for about $75.

    I'm not sure if anyone is interested in this, and I hate documentation, so if y'all want to build one reply here and I will post the specifics.

  2. #2
    Join Date
    Dec 2001
    Posts
    603
    Quote Originally Posted by Tiros
    I distribute my Tivo's to all TV's in our house using RF.
    Terk Remote extenders relay IR to the basement where the Tivos live. I use a notch filter to wack out cable above channel 70, and insert my Tivo's RF there. Every room has a URC6131 JP1ed to control multiple Tivos and the AV gear relevant to that room. Bottom line is every room can watch cable or any Tivo with only one remote per room. Although RF modulation is not the "best", it avoids deploying an Xbox at every set, uses existing coax wiring, and provides a clean uniform "UI" for controlling the gear in any room.

    The "main" set uses optical audio/svideo for best quality. Some TV's in the house are Stereo and most modulator's are mono. Stereo modulators cost a fortune (~$500-$1000). Radio Shack sells a frequency agile "mono" modulator that can output on any channel for about $30. They also sell a "channel 3/4" modulator that is stereo for about $30. My hardware hack allows these 2 modulators to work together to produce stereo RF on any channel for about $75.

    I'm not sure if anyone is interested in this, and I hate documentation, so if y'all want to build one reply here and I will post the specifics.
    I actually modulate 6 channels on my cable above 70, using a notch filter to kill the cable. All devices are actually in the basement, not near any tv. I use the terk phone line leapfrog system to send ir back to the basement.

    I also send component/a-v/spid-f for all devices, up to the den, where the big screen 62" mits is located

    So......
    YES! I was about to try this exact thing. I actually have the rs 3/4 modulator and was going to try to get a freq agile one to see how to combine them.

    Please post!
    Last edited by philhu; 10-06-2004 at 11:35 AM.

  3. #3
    Join Date
    Jul 2002
    Location
    Texas
    Posts
    102
    I am also interested.

    I checked Radio Shack's website, but could not find.....
    "a frequency agile "mono" modulator that can output on any channel for about $30"

    Do you have a part number?
    Thanks,
    Red Dog

  4. #4
    Join Date
    Feb 2003
    Posts
    155
    Oh Oh,
    It seems the frequency agile #15-1243 may no longer be available. Some stores may still have them.
    The Stereo unit #15-2525
    http://www.radioshack.com/content/pr...5.asp?cat=003d
    Is really the key. It uses a Motorola
    http://www.freescale.com/files/app_s...t/MC44C401.pdf
    Stereo Encoder.

    The Stereo 1525 has 2 sets of AV INPUT jacks. After the mod, one set is INPUT the other set becomes OUTPUTS.
    You connect your Tivo to the 1525 input side, then connect another set of cables from the 1525 "output" side to the mono modulator audio/video input.

    The video needs to pass through the 1525 so that the Mot. chip can properly create the stereo subcarrier. The 1525 mods involve removing the 75 ohm terminator on the video input line, electrically isolating the "new" output jacks so they can carry output signals, connecting a jumper wire from the video input to the "new" video output, and routing the composite stereo output of the Motorola to one of the "new" audio output jacks in a similar fashion.

    Once completed the unit can "sit in front of" almost any mono modulator. I was using the 15-1243 mono for a while before I tried the hack. The only modification to the mono modulator is to defeat the audio pre-emphasis network. This is simply a resistor in parallel with a cap. This resistor/cap netowrk is pretty easy to find. Located right at the input the the modulator IC. The pretty much all have them. You remove them both and put like a 100k pot there instead. That pot will let you adjust the depth of modulation (the relative loudness) of the TV signal you are creating.
    That being said, you really don't have to modify the mono modualtor at all. Your audio response will sound like the treble is up a bit. It will not affect stereo seperation/operation.

    For the 13-2525 Stereo mod, all you really need is the R# for the 75 ohm resistor that must be removed and the contact point for the Motorola chip stereo output. I can also post the location of the pre-emphasis network in the 15-1243 mono as well.
    I took some notes (R#'s and values) when I did this, tryin to find 'em, if I can't I'll open her up for a peek.

    Does anybody intends to do it? Philhu?

  5. #5
    Join Date
    Aug 2003
    Posts
    2,149
    This sounds very interesting. I may not have time but I'm subscribing to the thread and will research your methods soon.

    It really sounds pretty good to me.

    Thanks for your fairly detailed post. I haven't really got a handle on all the possibilities I think


    NutKase
    "God, and DealDataBase, help those that help themselves." --Shamelessly stolen from psxboy
    ------------------------------------------------
    2 each, SA S2 287hr 7.2.1a's with Lifetime.
    Hacks: 1 Manually Monte'd -140, Bash,Telnet,FTP,TivoWebPlus,
    Superpatch-67all Unscrambled/HMO,MFS_FTP Ver. N,TyTools, tivoserver
    Fully hacked SA S1

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