Max length of RG6 coax cable ???

RBM · 2007-08-05T18:02:17+00:00

I'm sure there are variables and information that I don't currently have, but the situation is this:Local cable company was supplying TV and internet via an underground RG11 cable that ran 500 feet to a two way splitter. One split to two TVs and one split to the computer modem. The underground cable was installed and owned by the home owner. Lightning struck the line and destroyed it, which was confirmed by the cable company. I want to install a temporary overhead line, and would like to use RG6. The run will be shorter then the current underground, but I have no idea what the maximum distance is that I can get away with using RG6. Any help is appreciatedTIA, Roy

Aug 05, 2007 27 Replies

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dpb 19 years ago

Typically coaxial cables with 75W characteristic impedance are used for CCTV video signal transmission. Commonly used cable types are

RG 59/U with 22 gauge solid copper inner conductor and bare copper shield (diameter approx. 6mm). Example Belden 9659, 9259 etc. Many types of RG59 cables are available with varying characteristics. Belden 9659 has approximately 3dB/100m attenuation at 10MHz.
RG6/U has 18 guage solid copper inner conductor with 7mm diameter and has approximately 2.3dB/100m attenuation at 10MHz.
RG11/U Example Belden 8213 with 14 gauge solid copper inner conductor and copper shield (diameter approx. 10mm) has approximately 1.2dB/100m attenuation at 10MHz.

For reasonable video quality, RG59/U can be used up to 250m, RG6/U up to

400m and RG11/U up to 550m. Longer distances can be supported with the help of proper video amplifiers.

(1dB loss refers to a signal loss of approximately 11%; 2dB, approximately 20% and 3dB, approximately 30%.)

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Art Greenberg 19 years ago

OP is asking about an RF application, not a baseband video application. For cable TV, loss figures at 750MHz would be more relevant. I'm not in a position to obtain that info ATM ...

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dpb 19 years ago

OK, didn't notice that...

Relative will probably be pretty similar relationship relatively, just a higher loss...

Any way, all needs to do is look at some manufacturer spec's and see where they are. I just pulled that from a quick google...

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George 19 years ago

The OP is asking about a broadband not a baseband application.

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CJT 19 years ago

How's that, again? Maybe a better S/N, but how less loss?

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DA 19 years ago

I think you are going about it from a wrong perspective: I would say that if the cable company still wants your account, then THEY should repair the cable the way they see suitable for providing you with the required signal strength at your end TV connection.

In any case, how are you going to hook your temp cable up to their box, anyways? They will not let you in for sure.

And last but not least, you've had a lightning problem with a buried cable. I cannot stress enough that pulling an aerial run (and maybe even bypassing lightning arrestors as they now may be in a wrong location) is simply inviting MUCH more trouble.

And, no, RG6U is not going to cut it. Neither from the attenuation stand point nor for hookups to the cable company's street cabinet that should be receiving either .500 or RG11.

Good luck!

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RBM 19 years ago

I suppose cable company laws vary from place to place. In this location the cable company wouldn't run the underground, so it was done privately, and they made the connection to their equipment at the pole. With the line blown by lightning we ran a temp RG-6 over the grass 400 feet from the main splitter to the pole and the cable company connected it... it works fine

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