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    Powermid RF carrier question.

    Hi,
    I'm going to buy Powermid XL.
    I've got a question: does Powermid transmit via RF, only when it receives an IR signal, or ever?

    Thank you.

    #2
    Hum... I'm not sure I understand your question. They (a set) basically waits till the receiver receives an RF signal and then the receiver sends that signal to the transmitter.
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      #3
      I don't have powermid, but the brand I have is really dumb - probably like all of the brands: When an IR carrier (38KHz) burst is detected, it sends that same pulse duration - which is typically 1 mSec - on the RF link to the receiver (900MHz band or 433MHz, usually). The receiver regenerates a (typically) 38KHz IR burst. I don't believe that they operate at the IR carrier freq per se (38KHz for most appliances).

      Due to RF interference from other unlicensed transmitters, and due to a really simple/cheap RF receiver design, my receiver emits a lot of "noise" on the recreated IR signal. This is mostly ignored as invalid IR data by the appliance.

      So the RF transmitter uses simple carrier (say, 9xxMHz) on/off keying, triggered by the detected IR on/off keying. The RF receiver just looks for signal present (above a noise floor threshold) - and this is the vulnerability.

      -------------
      I send my IR from the living room to the garage using a signal injector for the RG6 TV coax. It sends DC signals on the coax and thus is a true recreation of the IR timing and is not prone to noise and interference. IMO this is much preferrable if you can use the coax approach. Inexpensive too, like $35 for the pair.

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        #4
        Originally posted by Stevech
        I don't have powermid, but the brand I have is really dumb - probably like all of the brands: When an IR carrier (38KHz) burst is detected, it sends that same pulse duration - which is typically 1 mSec - on the RF link to the receiver (900MHz band or 433MHz, usually). The receiver regenerates a (typically) 38KHz IR burst. I don't believe that they operate at the IR carrier freq per se (38KHz for most appliances).

        Due to RF interference from other unlicensed transmitters, and due to a really simple/cheap RF receiver design, my receiver emits a lot of "noise" on the recreated IR signal. This is mostly ignored as invalid IR data by the appliance.

        So the RF transmitter uses simple carrier (say, 9xxMHz) on/off keying, triggered by the detected IR on/off keying. The RF receiver just looks for signal present (above a noise floor threshold) - and this is the vulnerability.

        -------------
        I send my IR from the living room to the garage using a signal injector for the RG6 TV coax. It sends DC signals on the coax and thus is a true recreation of the IR timing and is not prone to noise and interference. IMO this is much preferrable if you can use the coax approach. Inexpensive too, like $35 for the pair.
        Wow. Very complete response.
        Good idea to use TV coax.
        Thank's.

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          #5
          Originally posted by Stevech
          I don't have powermid, but the brand I have is really dumb - probably like all of the brands: When an IR carrier (38KHz) burst is detected, it sends that same pulse duration - which is typically 1 mSec - on the RF link to the receiver (900MHz band or 433MHz, usually). The receiver regenerates a (typically) 38KHz IR burst. I don't believe that they operate at the IR carrier freq per se (38KHz for most appliances).

          Due to RF interference from other unlicensed transmitters, and due to a really simple/cheap RF receiver design, my receiver emits a lot of "noise" on the recreated IR signal. This is mostly ignored as invalid IR data by the appliance.

          So the RF transmitter uses simple carrier (say, 9xxMHz) on/off keying, triggered by the detected IR on/off keying. The RF receiver just looks for signal present (above a noise floor threshold) - and this is the vulnerability.

          -------------
          I send my IR from the living room to the garage using a signal injector for the RG6 TV coax. It sends DC signals on the coax and thus is a true recreation of the IR timing and is not prone to noise and interference. IMO this is much preferrable if you can use the coax approach. Inexpensive too, like $35 for the pair.

          Stevech,
          Do you have a link for these. All of the injectors I see are expensive. Also does it have to be an "unused" coax or can the signal be sent on a used-for-cabletv cable?
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            #6
            Rupp,

            I was just reading about them at Smarthome.com: http://www.smarthome.com/8195.html.
            Plug-ins: UltraMon, UltraM1G, UltraCID, Ultra1Wire, UltraLog, UltraWeatherBug, UltraPioneerAVR, UltraGCIR

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              #7
              Cool! Thanks Ultra. It looks like they work "along" with the video signal. This is really a neat product.
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                #8
                For IR on Coax, I used ChannelPlus stuff
                Two different devices:
                MP2010 and
                MP2100

                One is a sender, the other is a receiver.

                I got the pair as a bundle from Home Controls, Inc - homecontrols.com
                for something like $45 including the IR target box (plastic box sits on top of your TV) and the IR emitter for the far end. Search their website for the bundle: 2010 + 2100 + target + emitter. Cost 2X if purchased separately. Maybe you can call them and ask.

                There's a crummy and out-of-date drawing of my setup on my website (login guest)

                http://childress.d2g.com/newweb/imag...0HA%20dwg1.jpg

                Comment


                  #9
                  Originally posted by Rupp
                  Stevech,
                  Do you have a link for these. All of the injectors I see are expensive. Also does it have to be an "unused" coax or can the signal be sent on a used-for-cabletv cable?
                  No- the idea of these IR-on-Coax products is to share the coax with TV/Cable signals. The ones I used have a built-in "DC block".

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