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RF cable question.
This thread has 4 replies. Displaying all posts.
Post 1 made on Tuesday November 8, 2005 at 17:45
tjlmbklr
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I have been getting quite a bit useful info on the forum. I am still trying to get all I need to upgrade to HD, and do it right the first time.

I am trying to figure out what quality RF cable is used on my current SD DirecTV dish. All I read off the cable is 18 gawg, so how do I tell the type RG59; RG6; RG11. And when I do, which of these (if not more) are the best. Keeping in mind I am running from the rear of my house(lower) to the upstair where I reside, at the front of the house. 60-70 ft. of cable.

And then there is the burning question, what do people mean buy the type of "quads" to use. And also does the Multi switch need to a certain quality also.
I love technology! I just need to figure out how to use it. Keeping up with it's growing rate is hard enough!
Post 2 made on Tuesday November 8, 2005 at 18:11
Daniel Tonks
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RG6 is 18 AWG. For reference, RG59 is usually 20 AWG, and RG11 is 14 AWG.
Post 3 made on Wednesday November 9, 2005 at 01:39
Ernie Bornn-Gilman
Yes, That Ernie!
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RG6 is the one to use, and is currently used by all cable and satellite companies I have ever run into. I saw one installation done with RG59 by a company that was used to running video for cameras.

RG6 is better than RG59 at running high frequencies, such as satellite signals, for long distances. All cables work better at low frequencies than at high frequencies, and it turns out that the thicker the cable, the better it is at the high frequencies. RG11, though, is around a half inch thick, VERY hard to bend, so not at all physically suited for home use. It's the stuff you might see running from pole to pole for cable distribution.

Quad can mean either of two things: quad cable or quad switch. A quad switch allows a dish to feed four satellite receivers. When there was only one (DirecTV) satellite, its LNB had two outputs. Those could be fed into a quad switch, which then gave four outputs. "Which kind of quad" could mean that. The current Phase III dishes have a multiswitch built into them, so they already have four outputs that can go to different receivers. But you can expand that with a 4x8 or 5x8 (the fifth input is for antenna or cable); four inputs are from the dish, and there are eight outputs.

There is also quad cable. Cable has, at minimum, a foil shield covered by a braid for keeping signals broadcast over the air from leaking into it. This is called dual shield, because each of those things is a shield. Quad is, starting at the foam core, foil, braid, foil, braid, outer cover. Four shields. Quad.

Quad is better than dual shield at keeping out interference. However, the need for the improvement is dubious in most setups. I installed and antenna system in a retail store about four miles from all the transmitting towers in the Los Angeles area, about as close as you can be while not up on the mountain, feeding about 450 TVs and some 40 FM receivers. I used RG59 and had zero interference.

In my experience, the definite reason for me to use Quad shield is so that no other installer, or smart-ass friend who doesn't really know the facts, can look at a client's installation and say "oh, he think this through enough to put in the really good stuff, did he?" Cable companies are rightly paranoid about signals both getting into their cables and leaking out, so their universal use of RG6 makes sense; it just ensures that amateur installers (most cable guys) are more likely not to cause problems.

By the way, about interference -- to be interference, it has to be on the same frequency. To get interference on your satellite cable, you would have to be within a half mile or so of somebody using 950 mHz to 1450 mHz, just above the top of the broadcast TV spectrum. This is highly unlikely.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 4 made on Wednesday November 9, 2005 at 11:35
Larry Fine
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If Ernie doesn't mind, I'd like to expand a bit on the explanation.

All cable has signal loss over distance, typically expressed as X db per 1000 ft. The different types have different loss numbers, the RG-59 being the worst offender, and RG-11 the best (of the 3 types mentioned here).

Additionally, the loss increases with increasing frequency, so for any given application, one first determines the maximum frequency desired to be carried, the distance to be covered, and the acceptable loss for the use.

Braid shield always has some spaces between strands, so may approach, but quite hit, 100% coverage, while the aluminized mylar foil is always 100% coverage. Quad-shield is very overrated and not mandantory.

Years ago, I lived in an an area that had cable-TV with dual-coax runs (120 channels), and I collected a couple of spools of dual-shield RG-59 dual-coax, so I used that in my home, because we have dual-tuner TiVos.

I'm only talking about the ruins from the multi-switch to the receivers; there is RG-6 from the dish to the multi-switch. The runs are around 50', and the RG-59 is adequate for these runs; picture quality is fine.
Post 5 made on Thursday November 10, 2005 at 18:47
Ernie Bornn-Gilman
Yes, That Ernie!
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On 11/09/05 11:35 ET, Larry Fine said...
If Ernie doesn't mind, I'd like to expand a bit
on the explanation.

I never mind an expansion!
And all well said.

The runs are around 50',
and the RG-59 is adequate for these runs; picture
quality is fine.

The signals are digital, so the picture quality will indeed be fine until it starts to tile and break up. You might even get more distance out of RG-59 with digital than with analog because snow will start to show up way before the signal is too low to use. With a digital signal, the signal will be completely usable until the two or three dB of signal level difference where it totally falls apart.
A good answer is easier with a clear question giving the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw


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