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Thread: UL Listed Coax for Transmitters

  1. #1
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    UL Listed Coax for Transmitters

    Hey guys here should be a fun topic for discussion with respect to Article 810 and 820 that is having a good debate on am Amateur Radio Forum. The topic is does UL listed Coax have to be used in a 810 application where a Transmitter is involved for Amateur Radio or CB?

    The question is not answered in 810. In 820 does require listed coax, but only refers to CATV 75 Ohm coax and ham radio operators do not use 75 ohm CATV coax. Ham radio uses 50 Ohm coax of varying sizes from RG-59 up to 1-5/8 inch hardline coax. Based on that I would say you are not required to use listed Coax for Ham Radio applications.

    What do you think?

    It might be answered in 800.179, but that is a stretch. Or 820.48.
    Last edited by dereckbc; 03-12-18 at 03:12 PM.

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    In my opinion the only article that applies is 810, and there is no requirement for the use of a listed cable.
    Don, Illinois
    Ego is the anesthesia that deadens the pain of stupidity. Dr. Rick Rigsby
    (All code citations are 2017 unless otherwise noted)

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    Quote Originally Posted by don_resqcapt19 View Post
    In my opinion the only article that applies is 810, and there is no requirement for the use of a listed cable.
    Long time no speak Don. Initially I would agree with you. Issue that keeps popping up is 810.3 with Coax cables refers to 820. The way I read 810 with respect to Transmitting equipment is speaking of Open Line, Twin Lead, or Ladder Line. All three are still used today but rarely and hold overs from WWII era. Today mostly coax is used, but it is not 75-Ohm CATV coax. Me thinks the NEC needs updated and we have a gray area. The coax I use is listed USE and there is CMP rated coax. But I cannot find any requirement to use any listed coax other than CATV application.

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    Anyone else want to take a shot at this?

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    Article 725 comes to mind. That is for fire spread though and has little to do with electrical safety.

    The issue I see with a transmitter feed is the RF power. How many watts is the transmitter capable of putting out? Several hundred watts of RF is certainly a fire and shock hazard.

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    Quote Originally Posted by dereckbc View Post
    Long time no speak Don. Initially I would agree with you. Issue that keeps popping up is 810.3 with Coax cables refers to 820. The way I read 810 with respect to Transmitting equipment is speaking of Open Line, Twin Lead, or Ladder Line. All three are still used today but rarely and hold overs from WWII era. Today mostly coax is used, but it is not 75-Ohm CATV coax. Me thinks the NEC needs updated and we have a gray area. The coax I use is listed USE and there is CMP rated coax. But I cannot find any requirement to use any listed coax other than CATV application.
    Yes, Dereck, it has been some time.

    I missed that in 810.3. That would mean that 820.113(A) would apply and require any type of coax installed for the Article 810 application inside the building to be a listed product, however 820.48 acts as a 50' exception permitting 50' of unlisted coax in the building.

    Any CMP rated coax would be fine in the building, but not sure about the USE listing. If it is like most building wire, USE without any other markings is outside only.
    Don, Illinois
    Ego is the anesthesia that deadens the pain of stupidity. Dr. Rick Rigsby
    (All code citations are 2017 unless otherwise noted)

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    Quote Originally Posted by don_resqcapt19 View Post
    Yes, Dereck, it has been some time.

    I missed that in 810.3. That would mean that 820.113(A) would apply and require any type of coax installed for the Article 810 application inside the building to be a listed product, however 820.48 acts as a 50' exception permitting 50' of unlisted coax in the building.
    Thanks Don, I found that later when someone else brought that to my attention. I knew there was a way around it, but like you it has been a while.

    Quote Originally Posted by don_resqcapt19 View Post
    Any CMP rated coax would be fine in the building, but not sure about the USE listing. If it is like most building wire, USE without any other markings is outside only.
    Agree but again 820 does not state CMP, only CATV variants. 50 foot rule is what I was looking for. THX

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    [QUOTE=Andy Delle;1902753]Article 725 comes to mind. That is for fire spread though and has little to do with electrical safety.]/QUOTE]

    Thanks but 725 does not apply.

    Quote Originally Posted by Andy Delle View Post
    The issue I see with a transmitter feed is the RF power. How many watts is the transmitter capable of putting out? Several hundred watts of RF is certainly a fire and shock hazard.
    That is why 725 does not apply because from a code POV a ham radio operator can operate up to 1500 watts. The other catch is impedance along the length of the antenna and coax varies with respect to operating frequency and phase, voltages can reach into the thousands of volts at high impedance points.

    As Don and I pointed out 810.3 was tripping me up taking me to 820 where coax listing is CATV 75-ohm coax which is not used in ham radio uses. 820.48 exempts using listed coax at entry point, aka 50-foot rule.

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    Quote Originally Posted by dereckbc View Post
    ...
    Agree but again 820 does not state CMP, only CATV variants. 50 foot rule is what I was looking for. THX
    820.133(A) just says that the coax shall be listed...it does not give any guidance as what it is to be listed as.
    Don, Illinois
    Ego is the anesthesia that deadens the pain of stupidity. Dr. Rick Rigsby
    (All code citations are 2017 unless otherwise noted)

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