Underground antenna cable from detached garage

PaulTurner · 04-07-2011, 11:20 AM

I'm going to run an underground antenna cable from a detached garage to my house. Voltage on the line will only be in the millivolt range, but it is an additional conductor between the structures. The antennas will be within the garage initially, but assume that they could be moved to a mast above the roof line of the garage in the future.

(1) I didn't get a lot of response to a prior thread. The one reply seemed to indicate that there aren't any particular requirements in the NEC as to use of conduit or required depth. Do you agree?

(2) Even if there isn't any NEC code to worry about, what do YOU want to see in a good installation?

AllanJ · 04-07-2011, 12:49 PM

I have seen descriptions where direct buried [b[power[/b] cable needs to be 24 inches below th4e surface and cable in conduit needs to be 6 inches below the surrface.

It is not critical for low voltage cables.

In order for you to run this antenna cable, the power feed, if any, from the house to ghe garage must have separate ground and neutral conductors, for a 120.240 volt feed that would be a total of four conductors. Intrinsically this part doesn't make any difference if out in the garage the antenna cable is not c9onnected to any booster or electrically powered device and is not grounded out there.

gregzoll · 04-07-2011, 01:21 PM

Keep in mind, the longer the antenna run, the more signal loss. You will find that long of a run will cause more headaches than it is worth. I would put the antenna on the house if you want to pick up the locals Over The Air, and just keep a antenna in the garage for the tv. out there.

PaulTurner · 04-07-2011, 02:17 PM

Thanks for the help, AllanJ and gregzoll. All comments from anyone with experience running underground antenna wire are welcome.

AllanJ, I've been doing a lot of searching since posting. It seems that NEC articles 810/820 do apply, and that I still need an antenna discharge unit where the cable enters the house. Is this correct?

gregzoll, I agree with you; unfortunately, there isn't a better location available. My house was built around 1915 and is covered in the original stucco. Under the stucco, I have a layer of pierced sheet metal that could do double duty as battleship armor. This is a great house for a paranoid schizophrenic -- TV, radio and cell phones all have very poor reception inside. The garage is just some nice old wood over 2 by 4s, with no inside wall or insulation. Also, it's not worth the risk to get up on my house's steep roof just for free HD television. I'd have to rent a cherry picker or put up scaffolding, and that would cost more than it's worth.

gregzoll · 04-07-2011, 08:08 PM

If you have to rent a cherry picker, that would be the same way to top a tower. If you have a brick chimney, that is another way to attach the antenna. I would hire a company that does this work if you do not feel like doing it. As for the stretch from garage to house, how far? You may be able to run from the antenna to a splitter, then feed one leg to the TV in the garage without amp, and when it gets inside the house in the basement, then hook up the amp there.

Check with either avsforum.com which has a lot of people that do OTA with satellite, also a local company that specializes in DBS systems, since they would also tell you what is the best amp, and which antenna for your area.

As for the NEC, as long as the antenna is grounded at the start, and when the coax gets to the house, you would have a static block with the ground wire (#10) connected to the ground rod outside, do not connect to the cold water. What surprises me, is OTA was huge not even forty years ago, and seems that most people have forgotten how this stuff works.