The joys of wireless technology

Discussion in 'C-Bus Wireless Hardware' started by MichaelCarey, Nov 23, 2007.

  1. MichaelCarey

    MichaelCarey

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    This isn't really a question, more a cry of anguish.
    I've been setting up an old Crestron system I bought cheap on EBay to control AV equipment and C-Bus in my home theatre. I gave up on getting the Crestron processor to talk directly to C-Bus via a PCI, I'm using dry relay contacts into a couple of bus couplers...
    ...but I started getting weird intermittent problems while trying to control the lights in my HT via my Crestron ST-1500C/receiver/processor. Long story short, the RF signal from the Crestron ST-1500C touch screen to the CNRFGWA Crestron wireless gateway is being interrupted by my C-Bus wireless network.
    They are both on 433.92MHz and are fighting for RF spectrum!
    When trying to do a dim function, pressing and holding the Crestron touchscreen button, makes the bus coupler send commands on the C-Bus network, these are also routed to my wireless C-Bus network and bingo, the Crestron system falls over.
    I can't see any way around this.
    Michael.
     
    MichaelCarey, Nov 23, 2007
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  2. MichaelCarey

    ashleigh Moderator

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    Sounds like the Crestron is either not backing off and re-trying, or the cbus wireless communication is making it have a serious barf.

    The only suggestion I can give is to use something like a PAC to take wired system commands, do a small time delay + conversion to an updated / modified command which it sends out, and which will be routed to the cbus wireless side.

    Its poxy, and it might or might not work.

    Failing that, you are stuck in the joys of shared spectrum :(

    C-Bus wireless has been extremely carefully designed to be tolerant of this kind of spectrum sharing (it backs off an re-tries if the medium is busy). Doing this is difficult and imperfect. It sounds like the Crestron gear is not doing a terribly good job by comparison. Can you get a firmware update for it?
     
    ashleigh, Nov 23, 2007
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  3. MichaelCarey

    MichaelCarey

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    The Crestron stuff is a brute force carrier on 433.92MHz, listening on a normal FM receiver you can "hear" it very strongly. By comparison, the Clipsal wireless network can't be detected, I think it uses spread spectrum modulation... or something like that.
    When I dial up 433.92MHz (70cm band) on my amateur radio and transmit, I kill both the Clipsal and Crestron wireless signals.
    I do have one way out, and that is to buy some older Crestron two-way wireless equipment on EBay which works on 418MHz. The older Crestron equipment can be had for quite reasonable prices if you are patient.

    *** EDIT ***
    I just picked up a Crestron STX-1550C 418MHz two-way touch screen for US$305, I'm currently bidding on a two-way gateway.
    This will cure ALL my problems C-Bus Wireless/Crestron interference issues.
     
    Last edited by a moderator: Nov 24, 2007
    MichaelCarey, Nov 23, 2007
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  4. MichaelCarey

    ashleigh Moderator

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    Clipsal doesn't use spread spectrum (at least not in the Australian product), but it does use high data rate, short packets. To comply with some regulations, the total transmit time measured in a 1 hour period must not exceed 1%.

    It sounds like the Crestron does not meet that 1% occupancy requirement, which would limit the countries it can be sold into.

    As far as I know, the 418 MHz equipment will interfere with some devices sold by competitors in some other countries (no names in a public forum like this) - in Australia its most likely OK. You may need to check if the frequency is permitted by the ACMA LIPD Class License though:

    http://www.comlaw.gov.au/ComLaw/Leg...77D8F3B91989A8ACCA2571B700835FC7?OpenDocument
     
    ashleigh, Nov 25, 2007
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  5. MichaelCarey

    MichaelCarey

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    When I first started looking at Crestron gear, distributed and sold in Australia, it was the 418MHz version. You are right with the Crestron one-way equipment not complying with the 1% over 1 hour rule, it has no concern for any other devices on the same frequency... it stomps where it likes as long as you are pressing a "button" on the touchpanel. :)
    I've never been a fan of the 433MHz LIPD system, it caused havoc with amateur radio repeaters including the one I look after in Port Lincoln. We had to get new frequencies allocated because industrial crane controls on fishing boats were causing interference.
    But it could be worse, at least we don't have Pave Paws military radars in this country, I bet C-Bus Wireless wouldn't work very well near one with an average power output of 145kW of RF deafening the receivers.
     
    MichaelCarey, Nov 25, 2007
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  6. MichaelCarey

    Don

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    It would be a pretty safe bet that you tested the C-Bus wireless signal with an FM 70cm receiver. The bandwidth of the C-Bus wireless signal is greater than 20kHz, and consequently the modulated signal sounds like noise to a typical FM receiver and the 'squelch' does not open. Even if you listen carefully with the receiver unmuted, it is very hard to pick. You would probably hear it in an SSB receiver though.... thank goodness the LIPD band doesn't cover the part of the band used for small signal work.
     
    Don, Nov 26, 2007
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