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OT Signal Propagation on HDMI Cable

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  • Paul Alciatore
    replied
    J, I am not sure that makes sense. Coaxial cable is almost always used with the outer shield GROUNDED. There is virtually zero chance of getting a shock from it, even if the outer insulation is completely stripped off and you are standing in salt water. I worked with high power transmitters that used coaxial conductors in the size range from 3" diameter, up to 6" and even larger. They carried power levels from 25 to 100 KW and the Voltages involved were surely dangerous. These coaxial lines had solid copper outer conductors which usually had zero insulation on them. NONE what-so-ever. It was standard practice, as part of daily/weekly maintenance, to go around the transmitter building and FEEL the coax near the connectors for any hot spots. This was completely safe as far as electric shock was concerned. The only dangers were either falling off the ladder you were using to reach the coax or, in extreme situations, a burnt hand from the heat.

    And there was real danger of arcs INSIDE the coaxial lines. Air was the standard insulator in these coaxial lines. Often they were pressurized with dry air. Some installations used dry nitrogen to increase the VOLTAGE RATING and therefore the power rating of the coaxial lines even further. In one transmitter plant where I worked, sulfur hexafluoride gas was used for an even greater increase in that rated Voltage. But in all cases, the outer shield was not insulated and perfectly safe to touch.

    Perhaps the Voltage rating given in the spec sheets for a small diameter coaxial cable, like RG-6 is only for the outer insulation. But if so, it is a totally useless spec and only there to allow the cable to be used in situations where the NEC has sway. However it is curious that when I take the Voltage rating of a Belden RG-6 cable with a 75 Ohm impedance and use it to calculate the power rating, it comes horribly close to what I recall as the power rating for cables of that size.

    Belden data sheet for a family of RG-6 cables:

    https://catalog.belden.com/techdata/...A_techdata.pdf

    The Voltage rating, in V RMS is near the bottom of the second page. If this spec is not intended to describe the internal ability to withstand arcing, it comes darn near to it. One thing that you have to remember about these ratings for cables that are intended for RF signals is that the insulation can break down after years of exposure so the internal insulation will withstand a lot higher Voltage if it is applied for only a few minutes or hours. darrys's test really did not prove much. He should have looked at the data sheets instead.

    It is also obvious from the data sheet above that these RG-6 cables are intended for low level signals, like cable TV, and not any higher level RF power situations.

    And as far as I am concerned and have said above, running a RF cable in a power conduit is just not a good idea. Keep them separate.



    Originally posted by J Tiers View Post

    The appplicable voltage rating is NOT what the cable innards will stand, it is the rating of the outer sheathing..... does THAT protect the rest of the innards sufficiently against a given voltage? THAT is what UL and the NEC are concerned with as far as voltage rating.

    Hardly anyone rates that for signal cables, although it is not unknown.

    Kinda like other cables, available as standard, or as "plenum rated" (so they do not make noxious smoke in a fire), a specialty usage that not everyone messes with.

    Leave a comment:


  • J Tiers
    replied
    Originally posted by darryl View Post
    .....

    Needless to say, the RG-6 didn't have a voltage rating on it-. I was trying to see if I could pass 10,000 watts through 1000 feet of it with low loss.
    The appplicable voltage rating is NOT what the cable innards will stand, it is the rating of the outer sheathing..... does THAT protect the rest of the innards sufficiently against a given voltage? THAT is what UL and the NEC are concerned with as far as voltage rating.

    Hardly anyone rates that for signal cables, although it is not unknown.

    Kinda like other cables, available as standard, or as "plenum rated" (so they do not make noxious smoke in a fire), a specialty usage that not everyone messes with.

    Leave a comment:


  • JoeLee
    replied
    Originally posted by darryl View Post
    I once had the output of a color tv flyback transformer hooked into a piece of RG-6 coax. I had to strip the braid back nearly an inch before it wouldn't arc at the terminals, but the wire never shorted internally. I got some pretty nice arcs bringing the free end close to a conductor (and some non-conductors) and I could get the tubes in the tv set red hot. I don't think I could have gotten away with this with a solid state tv-

    Needless to say, the RG-6 didn't have a voltage rating on it-. I was trying to see if I could pass 10,000 watts through 1000 feet of it with low loss.
    I wouldn't have even attempted to put 10kw through RG6. That would be like trying to run 10kv through a lamp cord.

    JL................

    Leave a comment:


  • darryl
    replied
    I once had the output of a color tv flyback transformer hooked into a piece of RG-6 coax. I had to strip the braid back nearly an inch before it wouldn't arc at the terminals, but the wire never shorted internally. I got some pretty nice arcs bringing the free end close to a conductor (and some non-conductors) and I could get the tubes in the tv set red hot. I don't think I could have gotten away with this with a solid state tv-

    Needless to say, the RG-6 didn't have a voltage rating on it-. I was trying to see if I could pass 10,000 watts through 1000 feet of it with low loss.

    Leave a comment:


  • J Tiers
    replied
    Originally posted by JoeLee View Post
    Running any coax or telephone lines in the same conduit with electrical lines is a code violation.


    JL.....
    More specifically, any cable in with electrical lines has to have insulation that is rated for the highest voltage to ground that is in the raceway with it.

    There is basically no cable for TV etc that is actually rated for power line voltage and that is so marked, even though it might actually have functional insulation for the power voltage. The key is that it is not MARKED as rated for that voltage, so you cannot use it.

    Leave a comment:


  • JoeLee
    replied
    Running any coax or telephone lines in the same conduit with electrical lines is a code violation.


    JL.....

    Leave a comment:


  • Paul Alciatore
    replied
    Oh boy! Many questions. First, I have one about your cable system. My cable system changed to all digital a couple of years ago. Before that they had a combination of analog and digital. The basic channels were analog so they could be carried over the coax, even with splitters, and you could receive them with only an analog TV with the TV tuner. For that you did not need any cable "boxes" at all. When they converted to all digital, those analog channels went away and you now have to have a cable "box" at every TV. Those cable "boxes" output the HDMI signal so you need a digital TV to see your programs. So, my question, what kind of cable system do you have? Is it all digital? Or are at least some of the channels analog? (All HD channels would half to be digital. Analog (NTSC) channels would be the old standard resolution).

    If you have an analog cable system, there is no reason why a splitter would not work. The equipment to sense a splitter in an analog system would be quite sophisticated and expensive: I doubt that any cable system would use it for individual customers. That fact seems to point to an all digital system. You could try an RF amplifier instead of a splitter. If you like, I have one I can send to you. But I doubt that it would work.

    The problem that I see with a switch on HDMI cable is you still need to select the channel at the cable box. So, if you want another program you would have to go back to the house to change it.

    The range problem with HDMI cables is size. The cable carries the signals on twisted pairs of wires that are inside of individual shields. FOUR of those shielded, twisted pairs of wires plus about another set of four in a fifth shield and also some additional conductors are all inside that miniature, HDMI cable. All of them must be SMALL. And, when high frequencies are involved, smaller cables will have greater losses than ones that are physically larger. Greater range requires lower losses per foot and therefore, a physically larger cable size. Or amplification, but amplification has it's own problems. Using physically larger cables also has problems, primarily the miniature connectors used for HDMI. Large cables just won't fit.

    Generally, HDMI cables are limited to about 25 to 50 feet. But there are methods of extending them. Which you would choose may, at least partially, on the answer to my question above.

    HDMI extenders using coax:

    https://www.bing.com/search?q=coaxia...FORM=QBRE&sp=1

    I would suggest reading the specs. carefully before you buy.

    HDMI extenders using twisted pair cables:

    https://www.bing.com/search?q=hdmi+r...FORM=QBRE&sp=3

    Again, read the specs carefully before buying.

    "In line Amps"

    I would not have an amplifier outdoors unless it is made for such use or is protected in a completely weather proof case. But I suspect that the amps for these cables would be at the ends and therefore, indoors. So they should be OK.

    Then there is the cable itself. Some outer insulations are OK with sun and weather and others are not. Again, check the specs. You can always run it in conduit to protect it. But keep in mind that buried conduit will almost always flood after some years if there is even a single joint in it. Believe me, I have been there. It is going to be full of water - nasty water.

    I would not run HDMI or any of the extensions for it in the same conduit as power lines. This is probably against the code, and there is a great chance of picking up 60 Hz hum. That would be trading one problem for another. Make a separate conduit run and if it is not metal conduit, keep it at least a foot from any power runs. The best way to do this would be OVERHEAD instead of in the ground. You said it is only 20 feet between buildings. They sell pipe in 20 foot lengths.

    My solution:

    I had splitters and cable in my shop, kitchen, all bedrooms, den, office; basically all over the place. All digital cable killed that as they wanted me to have separate cable boxes ($8.95 per month) at each TV. NUTS to that.

    I have a WiFi router. I purchased several Roku Express streaming devices (about $30 each) which work with WiFi to get streaming video. My cable company has a Roku "app" (I hate that word - app). So I can get ALL the cable company's TV channels that I pay for via the Roku Express devices. And YES, that includes the premium channels that I am paying for. I can also get Amazon Prime video, which I happily found that I was ALREADY paying for with my Prime membership which I got for the free shipping. There are also other FREE streaming services including the Roku channel where I can watch free movies and TV shows that are a lot better than current ones IMHO. Most news services, like Fox, ABC, NBC, CBS, etc. have free streaming available if you look for it. I get ALL of that here in my office and bedroom while my wife is stuck with just the cable company's line-up with the cable box in the den. But she is happy. Win, win, win, win, win, WIN!

    And there are a host of streaming services out there: too many to count. I could find more free ones and buy any of the others that I want. Even the old TV networks have streaming services.

    That $30 for a Roku Express is a ONE time purchase, not a monthly rental. And it gets ten times the programming that the cable company offers. There are at least two versions of the Roku Express, one with HDMI output and one with analog, component video. In the shop I have an old, analog, NTSC TV which only has the antenna input. The Roku there feeds an RF modulator and then a short coax to the TV's antenna jack. I get all of the above there. I mostly just listen in the shop so I don't miss HD there.

    That's my solution. Problems? I am having an on-going fight with my cable provider about their service. They simply can not deliver the service that they advertise. But, streaming video will work with ANY internet provider so I could switch to another any time.



    Originally posted by old as dirt View Post
    I want to send cable TV signal to the garage. In the past I just used a splitter and coax to do it and it worked well. The new version of the marsupial cable system senses the splitter and won't work.
    However an A-B switch and HDMI works fine to go room to room in parallel.

    I want to run an A-B switch off my main cable box as it would utilize all the functions available. Distance is about 100'. I know there were problems of signal loss on HDMI cables at their inception.
    I see Amazon is selling 100' bundles with an inline amp.

    Has anyone made a long run the works? About 20' will be outside between the house and the garage. None of the ads say anything about exposure to weather. Some say for in wall use.

    In the next few months I have to upgrade the electric service to the garage to use my tools and I plan to bury the feed in plastic conduit. Can the HDMI cable go into the 240/120 conduit with the electric feed or in a separate conduit.

    I love the HDMI for hooking up. Not very knowledgeable about digital signal propagation on.

    Comments, suggestions.

    Thanks
    JLG

    And YES I am a cheap SOB that resents having to pay an extra $7+ a month.

    Leave a comment:


  • doctor demo
    replied
    Usually Telephone and or TV are a minimum of 12" from secondary electric conduit, some authorities require 18" separation,and never allow anything in the same conduit.
    You can search "joint trench" for your area to see what is required.

    Steve

    Leave a comment:


  • Bented
    replied
    Your marsupial connection is faulty, try keeping the offspring in your pouch for several months (-:

    Leave a comment:


  • The Artful Bodger
    replied
    Maybe expensive? A wireless option https://thewirecutter.com/reviews/th...o-transmitter/
    John

    Leave a comment:


  • old as dirt
    started a topic OT Signal Propagation on HDMI Cable

    OT Signal Propagation on HDMI Cable

    I want to send cable TV signal to the garage. In the past I just used a splitter and coax to do it and it worked well. The new version of the marsupial cable system senses the splitter and won't work.
    However an A-B switch and HDMI works fine to go room to room in parallel.

    I want to run an A-B switch off my main cable box as it would utilize all the functions available. Distance is about 100'. I know there were problems of signal loss on HDMI cables at their inception.
    I see Amazon is selling 100' bundles with an inline amp.

    Has anyone made a long run the works? About 20' will be outside between the house and the garage. None of the ads say anything about exposure to weather. Some say for in wall use.

    In the next few months I have to upgrade the electric service to the garage to use my tools and I plan to bury the feed in plastic conduit. Can the HDMI cable go into the 240/120 conduit with the electric feed or in a separate conduit.

    I love the HDMI for hooking up. Not very knowledgeable about digital signal propagation on.

    Comments, suggestions.

    Thanks
    JLG

    And YES I am a cheap SOB that resents having to pay an extra $7+ a month.
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