types of coax cable
 

I am looking to purchase some coax cable with BNC connectors and I am seeing that there are a few different kinds--RG58, RG59, and RG6. What is the difference between the 3. I am looking to use it to run video from a mult box in outdoor conditions--could be in the rain.

thenks for the helps !

gotta love wikipedia :
RG58 is ethernet
RG6 is CATV and routing cable tv within buildings.
RG59 is used for low-power video and RF signal connections.

Hi Jeff.....
 

RG58 is co - ax, 50 ohm, good for VHF radio aerial links and the old co - ax type network connections

RG 59, 75 ohm, is an older co - ax than RG6, better at VHF than UHF

RG6, 75 ohm, is co - ax better suited to UHF runs, again aerial to telly, but for reasons I never figured out doesn't seem to be so good for VHF.

Not quite sure what a multi box is but if the signals are UHF and the impedences are 75 ohm, then go for the RG6.

Of course, if you're using miles of the stuff it would be better to make sure the cable perfectly matched the signal type and impedence

Jeff, I'm sorry but that's just not completely true. The big differences were already spelled out nicely by Chris. Mainly, the characteristic impedance of the different cable types. Most transmitters want to work into a 50 ohm load and RG-58 is used in low to medium power applications. There is also the much larger RG-8 for higher power 50 ohm impedance. The 75 ohm RG59 is typically used for CATV and TV antennas (with a 300ohm to 50 ohm balun attached at the antenna.

RG-58 has been used for ethernet, but keep in mind that it was in existence before the days of ethernet as a transmitter to antenna connection.

-gb-

In other words Jeff, if you're running a video signal to, or thru, this "multi box", use RG-59 or RG-6. RG-59 works well for fairly short distances (maybe a couple of hundred feet) RG-6 should be used for longer runs. Either will hold up well outdoors. Be sure to seal the connectors if they are exposed to the elements. (water)

If you were going to send 2-way radio signals or set up an old ethernet system, you'd use RG-58 or RG-8. Pretty much the same conditions apply.

Mark

Gotcha.
Thanks for clarifying--we are assembling a kit to plug into a news truck at the scene of a press conference or at a concert where we are using "pool" feed. The max run would be about 100 feet under normal circumstances. I found an RG-59 that I wound up with at one of those events, so I guess I will go with that.

Thanks for the input.

RG used to specify very precise "radio guide" numbers for military apps, and cables had to adhere strictly to the guidlines. Today, not so much.

For video, we use 75 ohm cables, so you're looking at RG59 and RG6. BUT there is a WORLD of difference between the construction techniques of different brand cables. You could have two identical looking RG59 cables, and cut them open to find that one has aluminum sheathing and braid and the other has pure copper. Aluminum shielding and video signals aren't friendly.

For long runs, use RG6 - the "Industrial" version of RG69. The insulation is thicker, the core is thicker, it has a foil shield to cut RFI between conductors and outside sources, it's more resistant to batterings. Again, not all brands are equal. Look out for dual or quad shield, neither are particularly good for video. Also, RG6 is commonly copper-coated steel conductor with aluminum or steel braid - better brands will use pure copper in both places.

http://www.smartwire.com/partnumber.aspx?id=ca

Oh, one more thing - RG6 is apparently more suited to HD-SDI frequency signals. If you're planning on keeping the cable for a few more years, may as well get the thicker stuff better suited to HD.

Several years ago I installed my own digital satellite tv system. The manufacturer recommemded RG-6 coax from the dish to the receivers. The main reason being that RG-6 has shielding that RG-59 does not have. You will probably notice a price difference. You get what you pay for, right?

Both RG6 and RG59 have shielding, the difference is in how complete it is and how effective. You're absolutely right, you do get what you pay for, at least some of the time. There can be cheap cr*p and there can be expensive cr*p but you'll almost never find the good stuff cheap.

I've got some bad news for you, old son....
 

Ahem, but solid centre core cables of any variety are designed, in the main, to "fit and forget" ie. get it in, nail it down, and leave it be. In the case of SCC co - ax they are designed to "bow", not bend, and are not designed to be pulled, re - coiled or twisted. That's why the wiring in your house is SCC and the stuff on your appliances is called "flex".

Co - ax in general, and RG6 in particular, once "out of the box" is an absolute sod to do much with other than as above. It's almost impossible to re - coil without twisting and it will wrap itself around absolutely anything in it's path in the process.

In short, if you're planning on a flexible, out, down, use, re - coil etc setup, then SCC co - ax is, most definately, NOT the way to go. The central core, mostly steel but sometimes copper, will, in short order, fail from fatigue, usually in the weirdest spot, which, in an HF environment can give rise to the most peculiar symptoms - and it never looks like it's the cable!

So, my sugestion is, 'less you're into pulling out grey hairs, go for a cable designed for the job, which will flex, lay flat where it's put and generally never have to be given another thought.

Hope that helps!

Oh, if your next "Big Q" was going to be "so what do I use", tell us what I/P & O/P impedances are involved, frequency spectrum of the transmission and signal levels etc etc then I'm sure someone here will know just the ticket.

Cheers,

Chris