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Author Topic: Burying the Coax ?  (Read 401 times)
KC5DFP
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Posts: 103




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« on: October 26, 2002, 09:22:18 PM »

Hello and thanks for reading.

My questions are....  What are the benefits of burying coax? Will doing so improve the transmit/receive performance? If so how deep should the coax be? I have a vertical (Cushcraft MA5V) and 2 G5RV Jr. antennas all using RG8X (mini coax).

Thanks for your response!

Joe
KC5DFP
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AC5UP
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Posts: 3869




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« Reply #1 on: October 26, 2002, 10:49:11 PM »

Aside from the health benefits of the exercise and quality time spent with your shovel, it's a mixed bag...

Bury the coax a foot or so (one shovel depth) and you'll gain some lightning protection while choking any stray RF off the braid. You may hear a slight reduction in your RX noise level and see a cleaner transmit pattern. You'll also be hard pressed to munch the coax with your mower.

On the negative side, gophers and moles have been known to chew on the PVC sheath. There's also a very slight risk of your soil chemistry reacting with the PVC and that can encourage soggy coax. If you bury the line, think about running it inside irrigation tubing as added protection against deterioration.

In my case, I've found cable laid on the turf will work its way down to ground level inside of a growing season. It's well below the mower blade and invisible under the thatch, but easily pulled up if needed. Since it's in a low-traffic area there's little chance of damage, but if it were in a 'busy' part of the yard it would have been buried...

- AC5UP
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AC5UP
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Posts: 3869




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« Reply #2 on: October 26, 2002, 10:49:40 PM »

Aside from the health benefits of the exercise and quality time spent with your shovel, it's a mixed bag...

Bury the coax a foot or so (one shovel depth) and you'll gain some lightning protection while choking any stray RF off the braid. You may hear a slight reduction in your RX noise level and see a cleaner transmit pattern. You'll also be hard pressed to munch the coax with your mower.

On the negative side, gophers and moles have been known to chew on the PVC sheath. There's also a very slight risk of your soil chemistry reacting with the PVC and that can encourage soggy coax. If you bury the line, think about running it inside irrigation tubing as added protection against deterioration.

In my case, I've found cable laid on the turf will work its way down to ground level inside of a growing season. It's well below the mower blade and invisible under the thatch, but easily pulled up if needed. Since it's in a low-traffic area there's little chance of damage, but if it were in a 'busy' part of the yard it would have been buried...

- AC5UP
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AC5E
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Posts: 3585




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« Reply #3 on: October 27, 2002, 10:29:10 AM »

Hi Joe: There's not much radio related benefit to buring cable here in fiveland -  

UNLESS you need to run coax under power lines, out of the way of lawn mowers, or out of reach of overenthusiastic vandals with pocket knives. In those cases, yes, for safety's sake I would bury my coax.

If burial is desirable, DO remember that shallowly buried cabling is much more likely to be hit by lightning than suspended cableing.

So DO bury a heavy ground wire a foot or so above the buried cables, make sure the sacrifice wire is well grounded, and if you decide to use a metallic conduit make sure it is grounded to a separate ground system.

That is; 8 foot ground rods on 16 foot centers for the sacrifice system driven on the right of the trench, alternating with 8 foot ground rods 16' OC driven on the left side of the trench for the conduit. And never shall the two systems be connected anywhere!

73  Pete Allen  AC5E


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WA9SVD
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Posts: 2198




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« Reply #4 on: October 27, 2002, 11:27:52 AM »

Not all cable is suitable for burial.  Make sure your cable is approved (by the manufacturer, not the vendor; he might want to sell you new cable every few years) for that application.
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WB2WIK
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Posts: 20595




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« Reply #5 on: October 28, 2002, 02:56:20 PM »

RG8X is not direct-bury cable from any manufacturer I know of (and I've looked).  If you protect it inside something that will keep it from coming in contact with the soil, and protect it from rodents, etc, it should be fine.

Still, since "buried cable" invokes visions of something that won't be easily changed, I'd use something better than RG8X to bury!  Probably RG213/U (regular mil-spec) or DB RG213/U "direct burial" rated product would be a better choice, to help assure you won't be required to change something that isn't easily changed.

WB2WIK/6
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