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Coaxial cable without a connector

Discussion in 'Electronic Repair' started by [email protected], Feb 9, 2008.

  1. Guest

    I've got the main cable-tv cable leading from outside the apartment
    into an opening in my storage room. That cable is attached to a
    splitter so I can join the four cables which run to the four jacks
    throughout my apartment.

    One of those four cables does not have an RF connector on end of it.
    The cable is just bare, with the pin (core) and the various sheathing
    of the cable exposed.

    Even without a connector to screw the cable onto the splitter
    securely, the signal works good enough if I just slide the pin into
    the spitter.

    My question: will this create any type of hazard? The cable tv
    company wants to charge for a housecall just to come out and put a new
    connector on the end of this cable. But I'm wondering if it's safe
    enough just to stick the pin in and wrap some electrical tape around
    it to hold it in place? Anyone know?
     
  2. Baron

    Baron Guest

    You can buy the proper connector very cheaply. 30 to 50 pence ea.
     
  3. gonzo

    gonzo Guest

    It's just a small signal to your TV, no high voltages or currents present.
    Having said that, couldn't you buy a connector and fit it yourself?
    The signal may be poor or intermittant, the outer shielding should be
    connected also.
     
  4. Charles

    Charles Guest

    No hazard but if you want to do it right:
    http://www.satcure.co.uk/tech/fconn.htm
     
  5. jakdedert

    jakdedert Guest

    Granted, no hazard...in a similar situation, though, an improperly
    terminated coax plug in my house caused a lot of ghosting on the rest of
    the system. Once I properly dressed the cable, applied a connector (new
    types require nothing more than a pair of wirecutters or even a knife to
    install), the picture on the rest of the sets in the house cleared up
    considerably.

    What was happening was the strong over-the-air signal was leaking into
    that unterminated connection. Where local channels corresponded to
    cable channels, the result was a 'pre-echo' on the screen. IOW, there
    was a ghost of the picture to the left of desired picture...messed with
    the sound, as well. This is similar to multipath distortion when a TV
    signal takes multiple routes on its way to an antenna. The different
    paths results in multiple instances of the picture displayed, separated
    by a distance determined by the time delay of each arriving at the set.

    jak
     
  6. Dave Platt

    Dave Platt Guest

    It can easily create RF interference problems, both to and from the
    cable-TV system.

    Cable TV uses many frequencies, on the cable, which are not "broadcast
    television" frequencies - they're assigned to other over-the-air uses,
    such as aircraft communications, police and fire, amateur radio, etc.
    Cable can use them without interfering with over-the-air users
    (normally) because cable TV is a "closed system". The outer sheath of
    the cable acts as a shield - the signals stay on the inside of the
    cable (the center conductor, and the inside of the shield) and don't
    travel to the outside.

    If you break the cable open, and don't connect the shield properly,
    you "open" the cable system. Signals inside the cable can "wrap
    around" onto the outside of the shield and can be radiated out into
    the neighborhood, causing RF interference with the assigned
    over-the-air users of these frequencies. Interference can also travel
    in the other direction - if a police or fire or ham-radio transmitter
    is operated nearby, the strong signal can leak into the cable and
    interfere with cable-TV reception on these channels. In a severe
    case, the outside interference can travel as far as a cable
    distribution amplifier, be boosted, and can interfere with or shut
    down cable-TV reception over a wide area. The worse case I've heard
    of involved a cable leak near the cable-TV company's headquarters... a
    nearby transmission saturated the amplifiers and shut down the whole
    town's entire cable-TV feed.

    It's important to maintain the integrity of the cable TV system and
    prevent "leaks". In fact, the cable TV companies are under legal
    obligation to do so, and they usually have "leak detector" checks of
    each neighborhood occasionally. If they find that your house is the
    source of a leak, they may insist that you fix it (or let them do so)
    or may disconnect your cable feed until it's fixed.

    I encourage you to install the proper "F" connector. They're
    available in both crimp-on and twist-on styles, aren't expensive, and
    should be available at your local hardware store.
     
  7. DCT Dictator

    DCT Dictator Guest

    Great explanation - add to it that more cable systems are now 2-way
    for VOD, VOIP and Internet. The return path is status monitored. If a
    troubleshooter is sent and cannot access the leak, he can shut off the
    feed to your apartment until access is granted.

    Buy a connector.
     
  8. Guest

    Thanks, Gonzo (and Baron). Yes, I will try to find a connector which
    I can install. My main concern was whether I could use that cable for
    a while BEFORE I got around to getting a new connector for it.
     
  9. Guest

  10. Guest

    Yikes. Talk about "for want of a...etc, etc". Assuming I can find a
    connector at the local shop, I promise I'll get it on asap.
     


  11. Sure Why not. I think the risk for interference that others were talking
    about is minimal. I have a tv that is hooked up that way right now, simply
    because I lost the connector and the tv is in my workshop. It doesn't get
    used too much so I really don't care if the picture is a bit snowy on some
    channels. If I were you I'd get a connector just to make sure I had a good
    picture.

    Mike
     
  12. bz

    bz Guest

    What you are doing is similar to the guy that goes out on new years eve
    and fires his gun in the air to celebrate. He has no way to know where it
    will come down. People die every year because of such things.
    You have no way to know what it might interfere with.
    It does NOT matter if the set is turned on or not. It only matters if
    there are signals on the cable!
    One of the cable TV signals might interfere with vital communications,
    such as with fire, police or aircraft communications or navigation.

    Now that you KNOW that you may be radiating signals that could interfere
    with communications, you have an obligation to cease.

    Deliberate interference with radio communications is a crime.




    --
    bz 73 de N5BZ k

    please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
    infinite set.

    remove ch100-5 to avoid spam trap
     
  13. James Sweet

    James Sweet Guest


    Interference in such a scenario is *extremely* unlikely. The power level is
    low, and a small unshielded section is a horrible antenna. On top of that,
    this would not be "deliberate interference". Putting a connector on there is
    a good idea, it's the only right way to do it, but there's no need for
    paranoia, there's nothing you could reasonably do that will cause any
    undesired interference to anything else.
     
  14. bz

    bz Guest

    Try listening on the shortwave radio bands near my house. The noise from
    switching power supplies, computers, dimmer switches, TV local oscillators,
    power line leakage AND cable leakage makes it impossible to hear any weak
    signals using a radio receiver that was quite fine in the 1960's {the Drake
    2B receiver}. My Electraft K2/100 does much better but the noise blanker
    MUST be used, otherwise only the strongest signals can be heard.

    The fault is not the receiver, it is the high level of noises.

    I do NOT have nor use cable TV. I get my TV signals 'off the air' with
    rabbit ears. I can often pick up sufficient leakage from the cable TV to
    view some programs.
    There are strong 'herring bone patterns on even the strongest local
    stations' due to cable leakage of signals from the cable.

    My 2 meter ham transceiver in my car often picks up strong interference on
    some frequencies as I drive around town.
    Some of the signals seem to be 'point of sale' devices that are radiating
    in the 144 MHz band.
    Some sound like TV video and some sound like wide band FM.

    Of course, some of these are 'mixing products' due to resonant structures
    that happen to have non linear conductance {rusty joints) that are picking
    up TV and other radio signals, mixing them together and radiating the
    products.

    I disagree with your assessment of '*extremely* unlikely'. I estimate it to
    be "unacceptably likely".

    The 'small unshielded section' is not the antenna.
    The antenna is the shield which is not connected at one end and the object
    at the end of the center conductor.

    The shielded cable can be many wavelengths long.

    The improper termination at the end causes standing waves. These standing
    waves appear on the outside of the coax. The coax radiates.

    The entire TV set also serves as a radiating device that is on the end of
    that piece of coax.

    Take a transmitter and feed it into a long piece of coax.
    At the end of that coax, hang a metal plate that is 19 inches by 19 inches.

    Feed it with 145 MHz signal.

    You will have a pretty effective radiator.

    Couple to the metal plate through a capacitor of a couple of nF and it will
    still work rather well.

    THAT is exactly what you have when you do not connect the shield on that
    cable to the TV.

    Here is a test you can do with a VCR and two TVs:

    Make a 'bad hookup' from the VCR to a TV in one room. Play back a tape on
    the VCR [putting a signal onto channel 2 or 3]

    Go to another room with a TV with rabbit ears and see if you can see any
    signs of the VCR's signals 'over the air'.

    I have seen signals from VCR's because people do not realize they are
    broadcasting.




    --
    bz 73 de N5BZ k

    I have held FCC 1st class Radio Telephone and 2nd class Radio Telegraph
    licences with Ship Radar Endorsement, TEA Certified Electronic Technician
    in Radio TV, Audio and Industrial Electronics.

    please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
    infinite set.

    remove ch100-5 to avoid spam trap
     
  15. jakdedert

    jakdedert Guest

    bz wrote:

    VCR modulators make fairly good transmitters. I once lived a few months
    in temporary housing, with little more than a TV and a couch for
    amenities. My neighbor hooked up her VCR to the TV by feeding the
    modulator output to the 300 ohm TV antenna input through a balun.

    So far, so good, except she left the rabbit ears connected to the same
    300 ohm terminals (in parallel with the VCR output). This was pre-cable
    era in the area...early 80's.

    I was able to get an acceptable signal from her VCR in the next
    apartment--through the wall and several meters away--by simply tuning my
    set (rabbit ears, again) to channel 3.

    She had a fairly good porn collection. <G>

    jak
     
  16. bz

    bz Guest

    That sounds like '"broad" casting' to me. :)




    --
    bz

    please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
    infinite set.

    remove ch100-5 to avoid spam trap
     
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