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#160057 - 05/16/05 10:08 AM Basic Coax TV Cable Questions
Romex Racer Offline
Member

Registered: 02/20/05
Posts: 60
Loc: Los Angeles, CA
What does the "U" mean in RG6U?

Can the same F type crimp connectors be used on RG6, RG6U RG6 Quad shield?

Must I use 75 ohm terminating resistors on unused splitter ports?

When looking into a piece of coax terminated in an F connector, must the inner, white dielectric be flush with the bottom or can in be back 1 or 2 millimeters? I sometimes can't push the cable in deep enough.

Is this true about coax connectors, basically the center conductor must never come in contact with the shield or connector and the connector must be crimped on top of the folded back outer shield so they are electrically common?

Can I "nest" splitters? Say there's a 4way now, 1 incoming and 4 coax leaving, but I want to add a 5th coax run. Can I remove one of the 4 exiting cables, add a small jumper to a 3way splitter, reattach the original cable to 1 port and my new cable to the other?

I have found 4 way splitters, (1 in, 4 out) but no 5 way. Is there such a thing?

At what point is a passive splitter not the answer and you need a amplified type splitter.

I wire houses, and am getting into home entertainment systems, are their any tutorials on the web for the best practices when installing TV coax?

Are there any inexpensive coax testers to validate my installation before the home owner plugs in their TV and receives no signal?

Thanks in advance, as you can see, I need a lot of help!

..........RR


[This message has been edited by Romex Racer (edited 05-16-2005).]

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Study Guides for VDV / Structured Cabling Installers
#160058 - 05/16/05 03:01 PM Re: Basic Coax TV Cable Questions
hbiss Offline
Member

Registered: 12/16/03
Posts: 893
Loc: Hawthorne, NY USA
Wow! Lots of questions. Lets take them one at a time.

What does the "U" mean in RG6U?

I have no idea. Somebody said that it meant "underground" but I don't think that's true. If it were you would notice it because the cable would be flooded with grease or goop under the jacket. Apparently it is a vestage of the original mil spec designation and anything with it I wouldn't want to use because it probably doesn't meet the requirements for the stuff we do today. If you have an example post the link, I would be interested in seeing who is selling RG-6U.

Can the same F type crimp connectors be used on RG6, RG6U RG6 Quad shield?

The difference in the outside diameter of the cable means that you need to use the connector designed for that cable and the companion crimper. There are some exceptions however such as the Gilbert USA line that will work with all RG-6.

Must I use 75 ohm terminating resistors on unused splitter ports?

You don't have to but it is good practice to do so. Terminating unused ports keeps leakage to a minimum which is something you should be aware of.

When looking into a piece of coax terminated in an F connector, must the inner, white dielectric be flush with the bottom or can in be back 1 or 2 millimeters? I sometimes can't push the cable in deep enough.

The dielectric must be flush with the bottom of the connecter. If it is too short you are not stripping the cable properly or the shield is bunching up under the jacket when you push the connector on. Keep in mind too that not all "strippers" will strip to the proper dimensions.

Is this true about coax connectors, basically the center conductor must never come in contact with the shield or connector and the connector must be crimped on top of the folded back outer shield so they are electrically common?

If the shield comes in contact with the center conductor the cable will be shorted. Most connectors require the braid to be folded back over the jacket to ensure continuity and minimize leakage. Otherwise the shield will bunch up and just be pushed back under the jacket not making good contact with the connector.

Can I "nest" splitters? Say there's a 4way now, 1 incoming and 4 coax leaving, but I want to add a 5th coax run. Can I remove one of the 4 exiting cables, add a small jumper to a 3way splitter, reattach the original cable to 1 port and my new cable to the other?

Sure. Matter of fact all splitters are multiples of 2 way's in one can.

I have found 4 way splitters, (1 in, 4 out) but no 5 way. Is there such a thing?

I havent seen one. How about a 3 and two 2's?

At what point is a passive splitter not the answer and you need a amplified type splitter.

When the signal level at each set drops below 0db.

I wire houses, and am getting into home entertainment systems, are their any tutorials on the web for the best practices when installing TV coax?

Not that I know of. Best teacher is experience. I always recommend that someone in your position works for someone who does this for awhile. Ther is a lot to learn.

Are there any inexpensive coax testers to validate my installation before the home owner plugs in their TV and receives no signal?

No, there aren't any VOM type testers. Signal level meters require some knowledge of CATV, frequencies and system operation to be useful.

-Hal
_________________________
www.myphonetechs.com

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#160059 - 05/16/05 03:37 PM Re: Basic Coax TV Cable Questions
Romex Racer Offline
Member

Registered: 02/20/05
Posts: 60
Loc: Los Angeles, CA
Hey Hal,
Thank you very much! That answers all my questions. Thanks for helping me.

Richard

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#160060 - 05/20/05 04:27 PM Re: Basic Coax TV Cable Questions
chipmunk Offline
Member

Registered: 07/20/04
Posts: 142
Loc: Southampton, UK
I found here that apparently the U stands for "universal".

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#160061 - 05/21/05 04:00 AM Re: Basic Coax TV Cable Questions
Sandro Offline
Member

Registered: 12/30/01
Posts: 449
Loc: Stoney Creek, ON, Canada
chip....an informative link!

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#160062 - 05/21/05 10:20 PM Re: Basic Coax TV Cable Questions
brianl703 Offline
Member

Registered: 05/16/05
Posts: 165
Loc: Manassas, VA
The RG6/U specification dates back to WWII if I remember correctly. "RG" stands for "Radio Guide" and was a military publication outlining specifications for cables.

In terms of modern cable, it means nothing more than a coaxial cable of 75 ohms impedance with an 18 gauge center conductor.

It does not specify the shielding or the type of dielectric (foam, solid plastic, etc.)

Typically cable companies recommend (at a minimum) double-shield cable with a 100% aluminum foil shield and a 60% aluminum braid and a foam dielectric. The foil shield should be "bonded" to the dielectric..that is, glued to the dielectric so it does not get pushed out of the way as you install the connector.

There is also "tri-shield" cable which consists of a 100% AL foil, a braid of usually 60% AL, and another 100% AL foil.

Then there is "quad-shield" cable which consists of a 100% AL foil, a 40% AL braid, a 100% AL foil, and a 60% AL braid. Comcast and Cox both use this cable for customer wiring. (Commscope F6SSVV is the brand and model of the cable they use).

All of these are usually specified with a "copper covered steel" center conductor for cable TV use, although they are available with a full copper center conductor.

Full-copper center conductor is recommended for CCTV and power-passing applications due the lower resistance of the center conductor.

For cable TV applications a copper-covered steel conductor is probably better since it's less likely to get bent up as the connector is plugged in.

Finally, we have single-shield cable which consists of a braid and no foil (typically this has a copper braid). This is OK for CCTV applications. NOT recommended for cable TV applications.

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#160063 - 05/22/05 09:48 PM Re: Basic Coax TV Cable Questions
Scott35 Offline

Broom Pusher and
Member

Registered: 10/19/00
Posts: 2724
Loc: Anaheim, CA. USA
I was wondering the same thing (whaddaheck does the "U" mean!?!?!?).

I remember it back in the "Thinnet Days" (10B-2 Ethernet), using RG 58/U &/or RG 59/U COAX LAN Cables.
( QUESTION: which one had the "Hollow" dielectric cover around the center conductor - which also had a like #18 Gauge plastic fiber spun around the center conductor? - the 58/u or the 59/u? )

Anyhow, other Cables with the "/U" deal (AFAIK):
  • RG 6/U - already mentioned,
  • RG 58/U,
  • RG 59/U,
  • RG 62/U,
  • RG 11/U.


Just my 2¢

Scott35
_________________________
Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!

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#160064 - 05/23/05 08:15 AM Re: Basic Coax TV Cable Questions
brianl703 Offline
Member

Registered: 05/16/05
Posts: 165
Loc: Manassas, VA
I've worked with both RG-58 and RG-59, neither had the fiber or the hollow dielectric.

I believe RG-62 had the fiber wrapped around the center conductor and the hollow dielectric, based on pictures I saw in catalogs. I never worked with RG-62 since it was already a cable for obsolete technology (Arcnet) by the time I started working on LANs.

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#160065 - 05/23/05 08:55 AM Re: Basic Coax TV Cable Questions
gfretwell Offline

Member

Registered: 07/20/04
Posts: 9045
Loc: Estero,Fl,usa
Yup RG62A/U has the monofiliment looking piece of plastic around the conductor centering it in the tube. That is 92 ohm stuff. IBM uses/used it for 3270 terminal cables. TV cable is 75 ohms (RG59 RG6), "Radio" antenna cable is usually 50 ohms (RG58 RG8).
_________________________
Greg Fretwell

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#160066 - 05/23/05 10:15 AM Re: Basic Coax TV Cable Questions
hbiss Offline
Member

Registered: 12/16/03
Posts: 893
Loc: Hawthorne, NY USA
There are (were) also B/U as well as the A/U designations and there are probably hundreds of different types of coax. Anything with the original RG designation is made to military specs which date back to WWII and before so you would have to refer to these if you want to know what this all means, and I seem to remember that the modifiers mean different things to different cables like solid copper, copperweld or stranded center conductors.

Probably a good place to find this information is in 1950-1960 vintage electronics catalogs (Newark and Allied) as well as Belden or Alpha catalogs of that time. Look up each type and compare constructions and specs. Those were the days when those cables were widely used and there were few that deviated from the original mil specs, unlike today.

Many of these original spec cables are still made today and are mostly used in communications and electronics. Some you are most likly to see are RG-58 and RG-8. these are 50 ohm cables used to connect antennas for CB, amateur and commercial radio. RG-58 was of course used for computer networking (thinet) before UTP replaced it. RG-59 is prefered for CCTV and other video uses. RG-174/U is a tiny sub-miniature 50 ohm coax used on Sirius and XM radio mobil antennas.

Just about all of the 75 ohm cables we have today that use the RG designation only use the RG designation as a size reference to the original. Everything else about the construction is completely different and to be accurate the cable should be refered to as RG-* type which some manufacturers do. Many just refer to the RG size in their literature and give the cable their own part number which is marked on the cable.

Interestingly there is a RG-7 size cable and I don't think there ever was an RG-7. You can see how the system works from this. RG-7 tells you is that this cable is a little larger than the RG-6 size and will have less loss.

-Hal



[This message has been edited by hbiss (edited 05-23-2005).]
_________________________
www.myphonetechs.com

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