sundance-communications.com/forum Forums Wiring - Telecom Carriers - Trunks & Services Cabling Telephones Systems Wiring Quad shielded coax

"RG-6A/U COAXIAL CABLE WONDERFUL"

It the label on the cable. Is this quad shielded? Do you need quad in a house?

Your cable can be single or quad. They both go by the RG-6 designation. Some of the higher end brands desi it as quad shield. If you have 4 layers, it's quad shield. Single shield is good but quad is best and never RG-59.

All RG-6 cable with an 18ga center conductor and a foam polyethylene dielectric will have similar attenuation vs frequency values. Shielding has nothing to do with attenuation so two or four shields will make no difference as far as cable loss is concerned.

Shielding reduces radiation from the cable as well as ingress into the cable from sources outside. In almost all cases these are handled sufficiently by a bonded foil shield over the dielectric which is then covered by a 60% braid.

In rare instances where the RF levels at the location are high (such as near a transmitter) or extra steps need to be taken to insure that the cable will not emit any RF (such as near an airport) quad shield cable will provide the needed extra shielding.

So, in MOST cases quad shield cable will provide no benefit, costs more and is more difficult to install because of its larger size.

As far as RG-6A/U. The original RG designation (radio grade or radio guide) dates back to before WW2. There were a very many coaxial cables of all sizes and constructions with the RG designation. Many are still available today made to the original RG construction standards usually with a solid polyethelene dielectric and a copper braid shield. The RG-59 usually preferred for video is an example of this.

The much superior RG-59, RG-6 and RG-11 cable that we normally use today for CATV and sat that has a foam poly dielectric and braid over foil shield is not an RG cable. The RG is only used as a size reference to the original RG cables.

I am not sure what RG-6A/U is, can't find it listed. The A/U would suggest it is a variation of the original copper braid RG-6, possibly with a solid poly dielectric, possibly with a stranded center conductor. If the center conductor is stranded it's useless with normal F connectors. If the dielectric is solid it would have a much higher attenuation (loss) than what we are accustomed to today.

Sounds like this is re-spooled cable that somebody is trying to get rid of.

-Hal

Hal,

thanks for the info. It was brand new cable purchased from Graybar. I thought it was quad, but from what you are telling me, it won't matter in a house for cable tv.

Dunno, sounds strange to me. Take a close look at it before you use it. The "A" in the A/U would indicate a stranded center conductor and that isn't going to work with an F connector, its just going to bend over when you go to screw the connector onto something. Cut a length off, strip it and look at it. If its anything but foam poly dielectric, foil shield, at least 1 braid shield and a solid center conductor it is of no use to you, don't waste your time- send it back.

-Hal

If I remember correctly (it's been about 5 or 6 years), the U designates "underground" meaning burial cable. Although it can be used indoors, it's not recomended, because of the "jelly".

[This message has been edited by tulsapoolplyr88 (edited April 26, 2005).]

A buddy who works for Comcast speculates that RG-6A/U may be a dual-purpose outdoor cable, the A/U meaning "Aerial/Underground".

He suggested that it's probably the gel-filled burial cable, but joined with a messenger wire for above-ground applications.

But as mentioned, not really practical for indoor use!

Just a general response.

The letter designation in a coaxial cable (ie, the "a" in an RG6 A/U) can mean anything, and varies from one flavour of coax to another. Coax started out as a Military Specification (MIL-Spec) family of cables; the way they worked was that the first allowed change in construction became an "a", the second a "b", and so on. I know that in RG59 A/U the "a" stands for a stranded centre conductor; in an RG59 B/U the "b" stands for a non-contaminating PVC jacket. But in any other flavour of coax, the "a" does not necessarily stand for the same thing.

If indeed this is a MIL-spec cable, then it would be solid poly dialetric, with 2 braids. The outer is a bare copper 95% and the inner is a silver-coated copper 95%.

If that's the case, then it's a very high-end cable, although the off-brand name is curious.


------------------
-Steve

If indeed this is a MIL-spec cable, then it would be solid poly dialetric, with 2 braids. The outer is a bare copper 95% and the inner is a silver-coated copper 95%.

Possible. I have use headend lashup cable that was something like that. Was (is) used to interconnect equipment in the racks at the CATV headend.

-Hal