Coax Cable: quality difference?

[Opus4]

Why is it so hard to find bulk white coax cable in local stores!? That's not my real question...

I'm getting tired of deciding to run a new line & then having to go buy a new cable, so I might as well buy a small roll & cut the length I need, as needed. Are there any cabling experts here who can tell me whether there really is that big a difference in terms of using 'regular' coax vs. quad shielded coax? Thanks for any info on that.

I would prefer white cable for the visible sections where I plan to run it (right around nose level, straight through the air across the kitchen. ), but quad shielded white cable seems hard to find, even in 100ft amounts. Radio Shack says some local stores have it, but for their price, I might as well buy a 500 ft roll elsewhere & let my kids play jump rope with it. Besides, while they show white cable online, the local store had black only for any decent lengths.

- Andy

[ToxMox]

I don't know anything about certain cables being better than others but here are some links with what you said you are looking for:
http://www.accessorywarehouse.com/ca...ex_tv_coax.htm
http://www.hometech.com/techwire/coax.html
http://www.jwswholesale.com/bin/cate...sp?category=73

[stanger89]

Here's what I use, it's a bit expensive to get started, but you end up with better than store-bought quality cables:

Canare L-5CFB RG6 Coax:
http://www.markertek.com/SearchProdu...L%2D5CFB&off=1
Canare RCA connectors (if you want video/audio cables):
http://www.markertek.com/SearchProdu...AP%2DC3A&off=1
Canare F Connectors (for RF cable):
http://www.markertek.com/Product.asp...&search=0&off=

Tools:
Die set for 5CFB/RCAP-C5F
http://www.markertek.com/SearchProdu...DD%2D5CF&off=0
Die set for 3CFB/RCAP-C3A (if you go with the RG59 cable)
http://www.markertek.com/SearchProdu...DD%2D35C&off=2
Canare Crimp handle:
http://www.markertek.com/SearchProdu...item=TC1&off=0

Here's some info on doing it:
http://white.hometheatertalk.com/diycable.htm

[korben_dallas]

I have a 20 foot plain old white coax running down the entertainment center, across a doorwell, behind the door, and then down the baseboard to my Plextor, and the quality is just fine. I'm more tempted to buy an amplifier/splitter than invest in cable.

I don't really remember where I got the cable. Maybe one of the cable contractors left it here. It does kinda look like Radioshack type workmanship though..

[Opus4]

ToxMox & stanger89: thanks for the links to check. (In don't think those search links for markertek work for copying to another system, though.) I was hoping to find something local so I could get it in a day or so, but ordering is always an option.

Korben_dallas: I'm not really 'investing' in better cable in terms of replacing existing lines; I need to run new lines more than 20 feet & I don't feel like buying long runs of premade cable.

But, like I said, my real question is: Is quad shielded cable really needed? (I still have to see if those above links mention that at all; but for sales purposes they would probably say 'yes'.)

Hmmm... I just noticed that when the cable company ran the line to my office for my cable modem, they used a roll of more than 50 feet of cable to go the last 4 feet from the wall to the modem! I guess I found some cable to start with.

- Andy

[mls]

Opus4 -

I haven't kept up on all the new variations of cable thru the years since my TV repair days, but...

In general, get low loss RG-6. Do not use RG-59, it's got very leaky shielding.

Unless you've got a lot of strange outside electrical interference, I doubt you need to worry about quad shielding. The main thing to worry about is signal loss in the cable otherwise.

What might be best and easiest for you to do is just call a local TV repair shop and ask them what they are using and were you can get it. Might even be able to work out a cut rate deal with them on a partial reel of what they have left.

Back in my day, I bought a 500 foot reel of RG-6 for less then $30 (roughly 6 cents a foot), but I doubt that you can find it for that price these days anymore.

[Opus4]

Originally Posted by mls

In general, get low loss RG-6.

Meaning: RG-6 is low loss in the first place, or find 'better' RG-6? (RG6 is what I was looking at anyway.)

Back in my day, I bought a 500 foot reel of RG-6 for less then $30 (roughly 6 cents a foot), but I doubt that you can find it for that price these days anymore.

It isn't too much higher: Home Depot (!) has 500 ft of 'coax cable' for $40-$45; quad (black only) is about $60. 100 feet of pre-finished cable for $20 seems like a waste, and especially so when it is $44 at Radio Shack!

- Andy

[mls]

Originally Posted by Opus4

Meaning: RG-6 is low loss in the first place, or find 'better' RG-6? (RG6 is what I was looking at anyway.)

RG-6 is sort of a generic designator for a specific type of coax. However, there are many variations of it as far a shielding, insulation, dielectric properties, etc.

For example, there used to be RG-6 with just a plain plastic dielectric (the insulation between the center wire and the shield) which has much higher loss then RG-6 with a foam dielectric.

Look for the info about the cable loss rating because the lower that is the better the cable should be (in general that is).

Oh, as a side point on that... be carefull about that loss rating also because the loss in coax varies in a reverse proportion to frequency. So you have to compare the loss at the same frequency (otherwise your trying to compare apples and oranges and it becomes meaningless).

Also, remember that every 3db is either double or half the signal (depending how you are referencing things). So, a 6db loss is 1/4 the power level, while a 6db gain is 4 times the power level. 9db would be either 1/8 or 8 times depending loss or gain reference, etc.

I don't want to make this overly complicated, but there is also a slope factor. Coax loses more as the frequency goes up. In general this used to be about a loss of 6db at double the frequency per 100 feet.

Cable companies boost the higher frequencies on their end so that the signal levels end up closer to equal on your end to compensate for this slop factor.

Sorry if I've got you totally confused now. Been a while since my amatuer radio days, and even longer since my TV repair days. It sure was fun though. Thanks for the memories.

[Menehune]

Quad shield is generally not needed for home use. If you have a higher quality cable with a foil shield and braid over it, the foil usually provides better than 99% shielding. Quad shield cables are generally thicker than others and are usually used for longer runs (think between buildings). The extra thickness may also require special connectors.

RG6 cables have slightly less attenuation in the lower frequencies (channels 2-13) but much less attenuation in the higher frequencies (compared to RG59). Belden 8281 (RG59) has 8db loss/100ft at 1000MHz and Belden 1695 (RG6) has 6db loss/100ft at 1000MHz. Basically your higher channels will have less snow and grains in the picture using RG6 than with RG59. Channel 78 is approx 750MHz, Channel 85 is near 1000MHz, IIRC.

[Endymion]

I'd say the easiest, likely cheapest, and probably still near best quality place to get coax is your cable company. Seriously, I worked for Cox cable in Kansas and while it varies from area to area of course, we had no problem giving customers a good chunk of cable for FREE if they just ask. I think the "official" limit was something like 25' with ends, but most people came in for shorter lengths anyway.
If you talk to someone nice when it isn't busy, they'll probably be willing to have a tech chop as much as 100' off a roll for you. A few weeks after I quit, I just walked up to one of the techs outside the building (didn't know the guy, he was new), and asked if he could cut me some cable, he spooled off about 75' and gave me 3 jumpers about 6' long and even put connectors on them for me!

From the perspective of the cable company, if you are going to do it yourself, they'd at least rather you have good quality cable so they don't have to send a tech out for bad reception caused by the crappy ratshack wire you bought last week. Give 'em a call, it's worht a try.

[SPHurley]

Quad shield was designed to help prevent signal leakage (egress) from the cable companies needs to use more bandwidth. Many of the frequencies on cable are "shared" with other forms of comunications, such as aviation, two-way, etc. Cable companies must comply with the FCC on a CLI (cable leakage index) their signals MUST NOT interfere with others on these bands. The quad shielding and better connectors and installation techniques have made that a reality. Now you as a consumer if you are extending the incoming signal from the cable company must insure that the CLI is in compliance. If an airplane was to crash as a result of your poor work you could be held at fault. Cable companies are always driving around "listening" to a barker signal to find leaks. If they find you at fault they will disconnect you until the problem is resolved. Bottom line is if you have cable for your source use Foam dielectric, copper plated center conductor (rf rides on the skin) with a good quad shield. IF its video you are playing with then you want solid copper center, 95+% COPPER braid, a foil shield is a bonus. Thats my two+ cents worth, Steve

[GbrNole]

i can highly recommend stanger's choice!

i always use canare product myself for both cable and connectors. the quality difference is pretty obvious when using it for making component video cables but less so for analog coax but it's the peace of knowing you have good quality product in place so signal is to blame.

quad shield doesn't make a huge amount of difference but avoid cables with molded plugs (like zenith brand etc.) that stuff sucks regardless of it being rg6 rated.

if you buy local then radio shack will cost a little more but they sell decent bulk cable. lowes and home depot can hook you up to but make sure to know what brand you are buying.

if all else fails call in a problem with the cable company and your technician will usually be nice enough to give you 50 or a 100 feet

[Opus4]

Thanks for all the input.

My cable co is Cablevision, but they just tried to point me to a particular electronics parts store instead of offering any cable. That's fine, though -- at least that could be a decent local source. I had to ask them to send someone out to rebury the cable that the township left lying above ground when they replaced some sections of sidewalk, so maybe I'll catch the tech sent out for that & try asking again.

In the meantime, I'm making use of that large roll of excess wire that I found behind the shelf where the cable modem is. I can't be doing too badly... I cut off the excess & put on a new connector. I'm now back online, so that means the cable still works & I must ha

[Opus4]

OK, one more question since I was talking about cables...

I'm curious: I think someone here told me several months ago that the total number of cable splits isn't what determines the final signal strength, but that isn't what I hear around here. (Maybe I'm talking to local doofi.) Every time the subject of splits comes up, people comment that the number of splits is what is important, not the db reduction at each split leading to a final connection.

What I was told _here_ makes sense to me, otherwise why else would I have a 3-way splitter that has 1 connection with a different db loss than the other 2?

The answer isn't critical, but I would just like to know. BTW: the line coming into my house must be boosted quite a bit -- now I'm up to 8 cable connections w/o having to use an amp: no cable modem disconnects and the TV picture still seems clear to me. On the other hand, maybe my TV picture would be absolutely perfect it there were no splits, as in: I've been looking through cloudy glass so long, I don't know what a clear day looks like.

- Andy

[korben_dallas]

Not sure if this helps any, but when the cable contractor came out to run a new jack, he looked at the setup I had for the TV & Sage PC and said I was using the wrong kind of splitter. He pulled one out of his truck and hooked it up. To be honest, I'm not sure I can tell a difference, but it was free so ok.

[stanger89]

There are a couple things that affect signal strength, both number of splits, but equally importantly, where the splits happen. Let my try some ASCII art to illustrate

Consider an example, 4 TVs, assume incoming signal is 0dB reference.

Case 1 - 4-way splitter

    /-> -6dB out
  0dB>-|-> -6dB out
    |-> -6dB out
    \-> -6dB out

Case 2 - Several 2-way splitters

     0dB->/-> -3dB out
   	 \-> -3dB ->/-> -6dB out
 				 \-> -6dB ->/-> -9dB out
 							 \-> -9dB out

Now you have the same total power, but notice that in case 1 each output has the same power, while in case 2 the outputs on the last split have 1/4 the power of the output on the first one. The signal can drop pretty quick when you start daisy-chaining splits.

[Opus4]

stanger89: That's the way I've been looking at this too, which is why I was keeping the lowest signal loss splits going to the modem.

The locals were trying to patiently explain to me that your case 1 & 2 would have the same results while I looked on in a bit of disbelief. I didn't even ask them about it, so it must be a favorite subject around here.

korben_dallas: Maybe he put in a bidirectional splitter. I know that at one point long ago I 'salvaged' an old splitter in my box of junk & killed my cable modem connection.

- Andy

[stanger89]

Originally Posted by Opus4

stanger89: That's the way I've been looking at this too, which is why I was keeping the lowest signal loss splits going to the modem.

That's exactly how our cableco hooked us up, one 2-way splitter with one line going to the cable modem, and the other going to a 4-way that feeds the various TVs.

From a practical standpoint, if you have a good signal, the "results" (what you see) will probably be the same, in that both ways you'll probably have sufficient SNR on each TV to get a good picture, but technically they're far from the same.

[mls]

Originally Posted by Opus4

What I was told _here_ makes sense to me, otherwise why else would I have a 3-way splitter that has 1 connection with a different db loss than the other 2?

It was for some time technically difficult to properly split a cable signal 3 ways equally while still maintaining a proper impedance match. So, yes, you will find older 3 way splitters that have one output with a different amount of loss than the other 2.

However, thanks to various technological advances, there are now newer 3 way splitters that do have equal loss on all 3 outputs.

As for stacking or chaining splitters, the goal is to make sure that the totall loss from the source thru the splits is as equal as possible at the end devices. It's better to use one larger splitter than chaining serveral because with one larger splitter all devices would get an equal signal level.

If you do need/use a splitter with more outputs, you might want to also put an amplier ahead of the splitter (with a gain equal to the splitter loss) to keep the level the same as the original.

Doesn't sound like you're having any problem with too much loss though or you would have already noticed it on one of the outputs (graininess, snow, possible inteference, etc.).

[Cayars]

Quality of cable is often overlooked. Use a cable with the least dB reduction. Most "high quality" cables are close to the same. The important thing is controlling the splits as stanger89 pointed out. If you know the dB rating of you cable per hundred foot you can calculate the loss per segment. Take this and add each split inline. So for example if you had a cable segment with 2dB loss and two splits each -6 dB you have 14 dB of loss for that segment.

Each 3 dB is a reduction in signal of 1/2. So 6 dB only leaves you with 1/4 of what you started with!

When you guys mentioned before that your cable guy uses a two way splitter coming into the house to split two feeds. One side goes to the cable modem and the other gets split again for the TVs. This is BAD.

Most cable modems these days are much more tollerant of signal loss then your TV/STB is. You should be able to easily check your cable signal strength on your cable modem and on your STB from the menu system.

What I normally do for people when hooking them up is taking the first 2 way split out and then removing the 3 or 4 way splitter and replacing it with a good quality powered splitter. This can make a world of difference!

If you only need a 4 way splitter I've had pretty good luck with the cheap radio shack 1-to-4 Bi-Directional Cable-TV Amplifier.

Another good way to split for 6/8 feeds is picking up a high quality passive splitter with 6 or 8 splits and putting the Bi-Directional Cable-TV Amplifier in front of it.

The only time I normally leave the two way splitter inline is when the cable modem is extremely close to the powered splitter. In this case you can easily overboost the signal. But if you know where to look in your devices you can check the signal levels and make sure you're in a confortable level.

The Radio Shack 4 way powered splitter has a screw driver adjustment that lets you adjust the level of boost. If you have a couple of long cable runs you would/could adjust the powered amp to bring up the signal for them. If you have a couple of TV/STBs very close to your powered amp, you can always throw a 2/3 way splitter on the short runs if needed to reduce the dB on those runs. This way all runs have approximately the same dB loss which then makes "tuning" the power amp easier.

A few bucks and a little thought put into the process can go a long, long way. Sometimes just noting which runs are plugged into which parts of the splitter will help. It's pretty normal to have a -6d and -9db loss on the same splitter. Sort of like a splitter within a splitter. Sometimes just moving the long run to a lesses dB loss will help and it didn't cost anything.

Carlo