What's the difference between these coaxial cables?

[Garibaldi]

Hi,

Here's what I would like to do with my setup, could you give me a hand in picking out the right cables? I currently have a Directv DVR in one room, and my computer with a capture card (coaxial in) in another room. I need a cord that is a minimum of 25 ft long, however 50 is also good if I decide to run it under the floor later. What I want to do is be able to transfer video from my DVR to the computer via the capture card, and then burn that video to DVD. I want good quality video, no interference or lines. My question is what are the differences between these cables and which one would be best for my situation/price?

Here are the links:
Link 1
Link 2
Link 3
Link 4
Link 5
Link 6

[lordsmurf]

Only real difference I see is brand and shielding. The better the shielding, the less the noise.

LINK 2 looks fine.

You can expect to pay about $1 per foot for good cable. Maybe a bit more of less. But around that.

Picking RG6 instead of RG59 was already a good move on your part.

[BJ_M]

false info regarding rg6 ... in FACT , some rg59 (foam core Serial Digital Video Cables such as liberty and belden) is better than most rg6 types .... they are good for 3ghz and higher - while catv dual and quad shielded cable is good for 1ghz to 2.4ghz most often ... the attenuation for 1000 feet is almost the same also ... dont confuse this with cheap standard rg59 though - where rg6 matv and catv cable is clearly better for longer runs ...

quad shield is still the best in high rf situations ...

for HDTV component - i swear by liberty rg59 serial digital cable .. and for long DVI - i find cobalt cables to have the best .....

hdmi - not sure who is the best - i ussually use geffen or liberty ...

[BJ_M]

btw -- radioshack cables are the pits ...as are thier connectors and adaptors ..

[Garibaldi]

btw -- radioshack cables are the pits ...as are thier connectors and adaptors ..

Do you have a link to some that you would recommend then?

Thanks for all the info!

[BJ_M]

https://secure.libertycable.com/

http://www.cobaltcable.com

http://www.gefen.com/


don't get suckered into buying real high priced cables either -- (like monster cable and even more expensive) - huge markup on cables and some are frankly just criminal in their costs ..

[ozymango]

false info regarding rg6 ... in FACT , some rg59 (foam core Serial Digital Video Cables such as liberty and belden) is better than most rg6 types .... they are good for 3ghz and higher - while catv dual and quad shielded cable is good for 1ghz to 2.4ghz most often ...

?????

Where'd you come up with this one?

I'm no rocket scientist, but I happen to be married to an electrical engineer. She could write you a (very long and incredibly boring) white paper on this kinda stuff but one thing she did learn me a long time ago -- ever wonder why cable companies (like cable TV companies, satellite TV delivery) use RG-6 cable? Not just because it's bigger, longer, and uncut ... or something like that ... ...

In a home situation it's probably not gonna be noticeable for drops of 50 feet or so but you've got this inverted -- RG-6 passes higher frequencies with lower loss. Period. Long complex electrical theory that I admit I can just barely follow sometimes, but like they used to say at the end of TV shows, you can read more about it at your local library.

Garibaldi, if you're reading, you also can look this up but having strung miles (literally) of all sorts of cables in my life (RG-59, RG-6, Cat 5, 12/2 Romex, ad nausuem), don't freak to much about any of this -- frankly RG-59 or RG-6 would probably do you just fine but yeah, I'd go with RG-6 and I'd just go down to my local electronic or home center and buy a roll of cable, a crimper, and some decent connectors and roll your own. I'm saying this because I suspect routing will be an issue and you'll get the best results, generally speaking, if you keep the cable runs as short as possible, avoid sharp bends, and run the cable perpendicular to any electrical wiring. If you end up going through walls it's a heck of a lot easier to pass a cable through without a connector, then crimp the connector on so you don't end up with 1" holes in the wall. My wife hates that, but YMMV.

[BJ_M]

ozymango, i am an engineer .... and have been responsible for 1000's of miles of cable being laid ...

You are probably confusing cheap rg-59 cable with better cables, in fact i specifiably above referred to serial digital rg59 ... also in fact the "RG" designation is in fact not used any more by the military (which dates back to 1942) ..

Serial Digital video signals are transmitted at very high data bit rates and should be handled quite differently than traditional baseband analog video lines. Typical digital frequency platform bandwidths range from 143 MHz for Composite digital video, 270 MHz for Component digital video and 360 MHz for proposed HDTV rate. Commonly used 75 ohm coaxial cables like RG59 dual shield and belden 8281 are generally acceptable for analog baseband video and may even be used for short runs of digital video transmission. But, in a modern facility system design where new SERIAL DIGITAL equipment installations require long tie lines and multiple I/O's, it is important to consider the 75 ohm Coaxial Cable selection along with "Impedance Matching" Connectors. Serial Digital cable is the same dia. as RG59 , but much higher bandwidth due to tighter control on manufacturing and better dielectrics and spacing - as well as impedance characteristics.

8281 is the defecto standard for many years in broadcast studios (along with triax) , but does not even match the bandwidth of serial digital rg59...

CATV cable, though very well RF shielded, has much poorer bandwidth characteristics, as picture quality. But is perfect for RF (i.e baseband cable). Sat. requires higher bandwidth (2.4 ghz cable and splitters should be used min.) , this is not always done of course and the results show in many installations ..

Liberty (and some others like Belden) offer such cables. The price is a lot more than RG6 and rg59 -- which in bulk cost only cents a foot ...


As for attenuation per 1000' - yes a solid conductor RG6 and more so RG-11 have less attenuation than even the best RG59 .. But the best RG6 has between 5 - 7.5dB and serial digital rg-59 has between 10-11 .. average braid shield only flex (non solid center) Rg6 also is in the 8- 14dB range.

If you have any other questions - I am sure I can answer them for you ...

[BJ_M]

btw -- also I have tested the radio shack connectors and most are in the 50ohm impedance range .....

always plan for the future is my suggestion ...

[ozymango]

ozymango, i am an engineer .... and have been responsible for 1000's of miles of cable being laid ...

Bully for you.

You are probably confusing cheap rg-59 cable with better cables, in fact i specifiably above referred to serial digital rg59 ... also in fact the "RG" designation is in fact not used any more by the military (which dates back to 1942) ...

No, I'm not confusing "cheap RG-59" with "better cables" -- as you noted, you aren't really talking about RG-59 cable, you're talking about something else. So based on that, Lord Smurf is still correct, RG-6 is better than RG-59 for the purposes and conditions described here, an important caveat. Yes, if we're talking serial digital, then that's something else. But I thought -- and I may be mistaken so if I'm mistaken, I apologize -- what Garibaldi is trying to do is move an RF or composite video signal over a coax cable. If that's correct, then RG-6 gives you less loss over the entire frequency range than RG-59, which is what he gave us to work with.

Yeah, okay, you say "RG-59" and you really mean serial digital cable and that's fine, but frankly you didn't make any initial effort to say anything clearly along those lines, and if we're hooking up component DVI then we can go off on all sorts of tangents but strictly speaking, what's this got to do with what Garibaldi's trying to do here? When you started going off on hdmi I figured you'd gone bye-bye on us.

Now, I will admit I may have misunderstood what he's looking to do, but as I read it (somebody correct me if I'm wrong), he's either trying to transfer an RF signal from his receiver to his computer's input card, or he's transferring composite video signal from his box to his capture card, and until and unless he tells us that's he got a DVI or component input connector on his capture card to connect his Direct TV DVR's DVI or component output, it's nuts to spend the prices on "serial digital cables" based on the links you put here, when he's looking at 75-ohm coax with F connectors from Rat Shack.

And the fact he's looking at 75-ohm coax with F connectors means (to me, anyway) that he doesn't need to drop a buttload of $$$ on serial digital video cables. And of course you certainly may disagree and offer your own info but I think it serves the end-user best to hear another perspective.

... Typical digital frequency platform bandwidths range from 143 MHz for Composite digital video, 270 MHz for Component digital video and 360 MHz for proposed HDTV rate. Commonly used 75 ohm coaxial cables like RG59 dual shield and belden 8281 are generally acceptable for analog baseband video and may even be used ...

Yeah, yeah, yeah thanks for the whitepaper. As I already noted in my previous post (if you didn't catch it) my wife's an electrical engineer so don't worry, I'm always ready for an engineer to tell me what's what.

Liberty (and some others like Belden) offer such cables. The price is a lot more than RG6 and rg59 -- which in bulk cost only cents a foot ...

Yeah, we got a roll of Canare L-7CHD in our server room and a bucket of BNC connectors, I still prefer to roll my own. What kind of connectors is Garibaldi looking for? What are his needs? I'm impressed that you spent so much time giving us a thorough background in coaxial cables, can you do the same for this persons actual needs?

If you have any other questions - I am sure I can answer them for you ...

Yeah, here's an actual question for you -- do you know what Garibaldi is trying to do here?

EDIT: A quick search on "Belkin Serial Digital Video Cable" on the web gets me a bunch of links for "Belden 1694A RG6 Coax precision video cable for analog digital and HDTV 3.0GHz Sweep tested."

Notice is says "RG-6" in there? Yeah, I know that RG-6 and RG-59 aren't so much "standards" as an old style sizing system that has all sorts of leeway (as opposed to standard wire gauge), so no need to update me on that. But bottom line again, as much as I hate to admit it, Lord Smurf was still right.

[lordsmurf]

... also in fact the "RG" designation is in fact not used any more by the military (which dates back to 1942) ..

Miltary? 1942? Please tell more. I like history.

[Garibaldi]

Thanks a lot for your help guys, I really really appreciate all that you're doing to help me out. I'll try to clarify what I'm trying to do so it is clear. I want to take the RF out (coaxial connection) on my Directv DVR, and hook that to my input on my ATI AIW capture card, this is also a coaxial connection, not RCA or DVI. I want to be able to take the digital video off the DVR's hdd and put it onto my computer, so I can burn it to dvds and have the video be good quality.

It sounds like the RG-6 is the best bet for me, is there any particular place ie Best Buy, Circuit City, ect that you would recommend?

Thanks

[lordsmurf]

Home Depot, Lowe's, Radio Shack, Wal-Mart

This sort of wire is more "home improvement" than "electronics" sometimes, I don't know why. Maybe because it's so common to outdoor wiring (satellite, cable, etc).

[ozymango]

Home Depot, Lowe's, Radio Shack, Wal-Mart

This sort of wire is more "home improvement" than "electronics" sometimes, I don't know why. Maybe because it's so common to outdoor wiring (satellite, cable, etc).

Total agreement from here. For something like this, your standard 25, 50, 100 ft. (depending on your needs) coil of RG-6 (I like RG-6!!! ) RF cable from one of these places will do ya just fine. I'd say "whoever's got it on sale" but I don't think I've ever seen coax on sale ... ... not that it's usually all that expensive. No need to buy anything too pricey, though! Oh, and get whatever color (black or white) doesn't clash too much with the walls and/or carpet.

What I've done for the pretty quick, cheap, and easy way: Go to Home Depot, in the wiring section, and get X feet of RG-6 cable off one of the big spools, however much you think you'll need (plus another six feet, just in case!) and either they or Radio Shack should have some "screw-on" or twist-on type RF connectors, where you just trim the cable ends to a certain length, and then "screw" the F connectors onto the cable, over the housing, so you don't need any tools to put it on. It'll make sense once you see these things, they're about a buck a piece. They're not made for studio work, but for household behind-the-furniture connections, they're fine.

The advantage to "rolling your own" is just that you don't end up with a big loop of cable at one end, and you can get some funky RF weirdness if you get loops of coax cable near power cords ... depends on walls and wires and what-not. Also it's pretty cheap, which is nice. But if this ain't your bag, your pre-made lengths should be fine.

And of course it's useful to test whatever configuration you end up with before you "permanently" hide the cable -- just connect the ends to the devices, check the picture, and move the cable around with everything turned on to see if you suddenly get ghosts or white noise or start picking up alien transmissions or whatnot. Then once it looks good, get out the duct tape and fasten it all down!

[Leoslocks]

Refering back to Radio Shaft, the Link 2 looks like what is being recommended.

RG-6 QuadShield RF Coax Cable with Threaded F-Connector

At $20, it is probably the more cost effective way to get the RF signal from the TIVO to the AIW. ( I am not sure this will give the result you are looking for. Getting this signal to DVD involves several more steps.)

Home Depot has a good selection of Bulk Cable, Short legnts of cable and connectors. Using the tools (Cable cutters and Crimpers) is easier said than done.

[Garibaldi]

That's an idea about cutting my own length, then I could get exactly how long I need, without that messy "intereference". That is bizarre that rolled wire would cause that. I see home depot has a couple cables on their site:
http://www.homedepot.com/prel80/HDUS/EN_US/diy_main/pg_diy.jsp?BV_SessionID=@@@@156829...4+6253&pos=n02
Both look the same except for the length. Not bad, 100 ft for the same price as the 25ft one from Radio Shack.

[ozymango]

That's an idea about cutting my own length, then I could get exactly how long I need, without that messy "intereference". That is bizarre that rolled wire would cause that.

Actually, come to think of it, for shielded (braided shield) coax RF cable this probably isn't that much of an issue, but I picked up this habit from my days as a roadie ... okay, I was never really a roadie but I used to help a couple of friends with a band they had for a while, until internal pressures caused one of those Beatles-esque breakups.

I've always been a lousy cable wrapper/coiler/whatever you call it to get your cables all nice and net. But my friend Bob showed me some tricks when it came to coiling (for storage) instrument cables and stage snakes and that kinda thing, and he learned me that when you're actually playing on stage, you don't want any looped cables (especially instrument cables) because it's got a spiral wrap shield. When it's flat, spiral wrap cable is pretty good at rejecting RF interference, but when you loop it, one side of the spiral wrap gets compressed (inner side of the loop) and of course the outside wrap on the loop "opens" up a bit, to compensate for the radius curve ... like if you bend a spring, the coils on one side get closer together and the other side opens up ...

Anyway, RF interference can then "leak" through the "open" side due to some complex radio wave propagation stuff that probably has a bunch of formulas and graphs to go along with it ... ... anyway, that's where I got that from and while I'm not sure (without doing a long web search on RF cable shielding) if this still applies to coax TV cable, it probably doesn't hurt to keep as few loops in the loop as possible.

Not bad, 100 ft for the same price as the 25ft one from Radio Shack.

To me, this is one of the "dirty little secrets" about most kinds of wires and cables -- the cable cost and end-fitting costs are often negligable, they just stick it to you on labor or however you wanna put it. Like you go to Office Max and they have a 25-ft. Cat 5 cable that the want to charge you $15 or more for, at least, and the cable cost is something like $2 and the ends are a quarter each (in bulk), so you're paying a massive mark-up for some guy (or machine, more likely) squashing those end connectors on.

Okay, to be fair, they use $$$ machinery and there are all sorts of associated costs with marketing, shipping, etc., but if you have to do a lot of wiring (of TVs, computers, whatever) in your own home, and had to pay retail for every cable to hook everything up (premade and ready to go), yow, you end up shelling out some serious $$$. And while it can take some "technique" to rolling your own network and TV cables, if you end up running a bunch of wire in your place (like me!), the cost savings in the end are considerable.

Anyway, I'm rambling now so I'll go, good luck on your setup!

[Garibaldi]

That explanation makes perfect sense, thanks for spelling it out for me!! Although like you said the specially shielded ones will probably not have that problem. I think I'm going to run out to Home Depot tonight (despite the snow) and pick up that 100ft cable. I did a quick estimate and it seems that the final length will be closer to 50ft but you might as well have more than not enough right?

[ozymango]

I did a quick estimate and it seems that the final length will be closer to 50ft but you might as well have more than not enough right?

Yup! Because there's anothor Law Of Wiring that goes something like, "The cable you have will be six inches too short for whatever it is you're trying to connect."

[Garibaldi]

Ok I just got the cable from Home Depot and I'm testing it out now between my computer and tv. I plugged it in and it was working fine on my computer and the sound was fine but then all of a sudden now the sound is all fuzzy. I tried swinging the cable a bit, no effect. This is the shielded cable too. I also tried a different PVR program and playing something else through my speakers, both are not the problem. Why would this be?

[Leoslocks]

Check the connector ends for any braided or foil ground wire touching the center conductor.


Try to keep the cable at least 6" from any electrical wiring.

[Garibaldi]

Check the connector ends for any braided or foil ground wire touching the center conductor.


Try to keep the cable at least 6" from any electrical wiring.

I'll make sure to keep it that far away, the connectors look fine. I also uncoiled the wire, which seemed to clear it up