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?
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.
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.
--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
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.
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.
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.
"Michael Kennedy" wrote in news:V-6dnQ-js8gtMi_anZ2dnUVZ snipped-for-privacy@comcast.com:
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.
bz+ser@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
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.
"James Sweet" wrote in news:WRHsj.191$sh.156@trnddc07:
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.
bz+ser@ch100-5.chem.lsu.edu remove ch100-5 to avoid spam trap
No hazard but the connection is not likely to remain good. That being said, I accidently pulled mine off and had every intention of running up to Radio Shack one day and getting a new connector. Its still being held in place with a water hose clamp after 3 years.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.