RG59u vs. RG59 cable

Hi,

Does anybody knows exactly when to use RG6 ?

Normally people use RG59U for CCTV. but I have seen some comments where they suggest RG6 for better quality. large distance. Does anybody knows about this distances. Any recommendations about cable for CCTV is most welcome.

only a 300' or so distance difference. Less inteference, if you can get it with copper braind and solid copper center, then it would be okay, but if it is like the cable TV coax or aluminum braid, quad, then leave it alone. If it is a short distance easy to change the wire and all you got is RG6 aluminum, then its up to you. Sometimes the Aluminum will work, but more than often it causes problems. Most of the time we cant buy RG59 down here at all, so alot of people are stuck with RG6 aluminum on short notice .. not me though ..

Id use UTP with some Active Hubs for long distances, direct bury if it is going to be in a harsh evnironment. Fiber if you have the $$$$$$.

rg59 they say can run up to 1000ft. (i would suggest only going about 800)

rg6 they say can run up to 1500ft (i would suggest only going about 1200)

Did you mean rg59 or rg59u ?

You gotta be careful when choosing RG59. Some manufacturers think RG59 is a brand name or model number, or simply 75 ohm cable, when in fact it is a specification for a specific purpose. The result is dodgy cable with all the right markings on it. Here is a recent tale of woe of mine:

We recently purchased some cable from a supplier at a regular price, installed it into a 26 camera installation, and found that the camera pictures all looked slightly washed out. Now this job was a pressure install from the get-go, so my chaps didn't question the cable from our supplier (complacency set in I guess) because Mr Customer needed the system going pronto. All of the runs were well within limits, and the cams were high-res GE models that give excellent pictures. Got the pattern gen & 'scope out and found that the sync pulse was badly mishaped and the peak-white excessive. We skinned back a little piece, held it to the light and we could practically see through the sheathing !! The centre core was lightly coated copper over a steel center (we rubbed it down with sandpaper) and had a DC resistance of 5.7 ohms for a 15M piece. We compared it to some previously purchased cable and measured a DC resistance of 2.2 ohms for the same length!! We ended up replacing all the cable and the pictures were crystal clear. The downside was that we lost on labour to re-install on account of us employing contractors due to rush-job and other teams all busy.

So my message with RG59 is; no matter how reliable your supplier, always check the cable, because its the one thing mostly overlooked that'll kick you in the #ss !!

PS The supplier took all the cable back and credited me for it with a nice letter of apology (still lost on the labour ). Seems he bought elsewhere due to over demand.

Sorry ... meant to say screen braiding not sheathing ...

And for those that don't handle cable that offen, telling the differance between the good and bad stuff is pretty easy. If you cut the sheathing off and the braid untangles almost instantly then it's the cheap stuff. If you cut it back and it keeps it's braid, and the braid looks nice and tight then it's the good stuff.

Does anybody knows the resistence (ohms) of a good RG-59U 1 foot piece ?

Using the multimeter can be a good way to check the difference. or not ?

i would suggest staying with the "Coleman" line of cable, especially coax. here is the link for the RG59 95% bare copper braid

http://www.colemancable.com

Thomas is right. A physical check should tell you whether it's good coax or not. A simple resistance measure of a fair length, say 5 - 10M, of good quality co-ax should serve as a yardstick by which to measure all other co-ax you get in future. Measure the centre core and the screen and put the specs & "test" in notice form in your store, along with a stripped down section of the good co-ax for a physical check. This way when your supplier delivers to you, you (or your storeman) can quickly compare a batch sample and accept or reject the cable right there and then.

It's like I said, it's not easy replacing dodgy cable. Dodgy equipment is a simple swop-out.

I just measured the resistance on a 50ft length of some thin Siamese cabling that I purchased.

It measured 3.9 ohms resistance.

how exactly do you measure the resistance on the cable? where do i place the test leads of the multimeter?

also, when you measure, lets say, 10ft. of cable, and it gives out 3ohms, does this mean you have a resistance of 3ohms per 10ft of cable?

Thanks

3 Ohms per 10 feet of cable sounds awfully high to me. For instance, West Penn 815 (RG59/U) specs are 10.1 Ohms/1M' Nom.. That would be approximately 0.1 Ohms per 10 feet.

You will probably not see much difference in short runs.

RG6 is generally for in-wall (i.e. longer) runs. The RG59 may flex better in tight spaces, since it's a bit thinner.

so which is an important factor to consider in proper signal propagation for CCTV? DC resistance or attenuation in dB?

With baseband video, they are equally important because they are basically the same. Coaxial cable attenuation at higher frequencies is primarily a function of cable capacitance. At lower frequencies, the DC resistance of the cable plays a much more important role.

That's why CCTV cable needs to be copper/copper. Copper has a much lower DC resistance per foot than steel. For instance, while RG6/U copper-copper has a nominal DC resistance of 6.5 ohms per 1000 ft., RG6/U with a copper-clad-steel center conductor and foil/aluminum braid has a DC resistance of 28 ohms per 1000 ft., making it usable for runs of only 100 ft. at best.

Since baseband video is primarily a low frequency signal, the DC resistance has a much greater affect on the cable's ability to transport the signal. That's also why RG6 can transport video for longer distances - its 18 gauge center conductor and larger diameter shield has a lower DC resistance than the 20-23 gauge center conductor and shield with less copper in RG59.

For instance, while West Penn 815 RG59/U has a DC resistance of 10.1 ohms per 1000 ft., their type 806 RG6/U only has a DC resistance of 6.5 ohms per 1000 ft.. RG11/U can go even farther, with a DC resistance of 2.6 ohms per 1000 ft. At the other end of the scale, you have RG179/U (WP 825), also known as mini coax. It has a DC resistance of 30 ohms per 1000 ft. and should not be used for runs longer than 100 ft.

Cable capacitance does have some affect on the higher frequency component of video. That's why the distance ratings are not linear. The DC resistance would affect the sync signal of the video more than the resolution since the sync is 60HZ and the higher resolution part of the signal is the highest frequency, as high as 10MHz. The color reference signal (color burst = 3.58MHz), is also affected more by the cable's capacitance.

A poor BNC connection, being high resistance, will cause the video to "lose sync" but have less affect on the color or resolution.

so which is an important factor to consider in proper signal propagation for CCTV? DC resistance or attenuation in dB?

Attenuation is the figure that most accurately reflects the impact of the cable on the signal, mostly at higher frequencies. As Survtech noted above, baseband video is more affected by DC resistance. However, most people do not have access to test equipment that can display attenuation in dB directly (or camera resolution, ), so DC resistance is the easiest test available to help troubleshoot / compare cabling.