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Author Topic: Running coax through galvanized pipe?  (Read 1408 times)
NI0C
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« on: January 18, 2007, 09:55:38 AM »

My present setup is limited to only one HF antenna because I only have a single coaxial cable running through a small (I think 3/4") PVC pipe that fits in a slot across my driveway. The PVC is mostly beneath the surface of the driveway, and I drive our cars over it regularly.  

Exapnding my antenna system will require running either multiple coax lines, or an additional control line across my driveway.  To bury the lines would require my digging out a bigger slot through my blacktop driveway, which I don't relish.  I spent days digging the present slot with a hammer and cold chisel.

Recently, I've been thinking about running multiple coax and control lines through a galvanized pipe that would simply lay across the driveway and create a small speed-bump.  Of course, I would fix the ends of the pipe in the ground on either side of the driveway so it would not move around as I drive across it.  Maybe a 1.75" to 2.0" pipe would fit my needs.  

However, I'm wondering if there are any problems that would be created by placing transmission lines through a conductive metal pipe.  Does anyone have experience with this, or have any other suggestions?

73,
Chuck  NI0C
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KB9CRY
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« Reply #1 on: January 18, 2007, 10:55:41 AM »

I see no problem with that but have to ask, why not attach the cables to your house and run them up and over the garage door?
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NI0C
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« Reply #2 on: January 18, 2007, 11:13:42 AM »

My house was built in the mid-1930's.  The garage, although attached to the house, is a rear entry one.  The room I use for my ham shack is near the edge of the property in front of the garage.

I really don't want to suspend the cables in the air where they are visible from the front yard.  Once the cables cross the driveway, they will be close to my wood fence where I can attach them to route them to where they need to go.

73,
Chuck  NI0C
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WB2WIK
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« Reply #3 on: January 18, 2007, 03:44:55 PM »

The pipe won't affect anything at all.

But if your antennas are for "HF," maybe you don't have to change anything.

You can use a remote coax switch (Ameritron, DX Engineering, Array Solutions, etc) on the "far" (antenna) end of the single coax line you have now, and run the DC control signal for that remote coax switch through the single coax line you have now, and use one piece of coax to feed several antennas without adding any wiring that crosses the driveway.

WB2WIK/6
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NI0C
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« Reply #4 on: January 19, 2007, 08:55:23 AM »

Good thought, Steve.  I may just do something like that to keep the pipe diameter to a minimum.  I've realized that, due to the slope of my driveway, a pipe laid across it may cause water to back up over the portion of the driveway in the back of the garage.  This could become a skating rink when the temperatures are below freezing!  

I do feel the need to replace my existing installation for the following reasons:

1. The RG-213 coax in the PVC is more than ten years old.  I want to replace it with Davis "Buryflex."

2. I want to put in at least one small diameter coax for use in experimenting with receiving antennas.

3.  I want to add some control line for switching one of the Force 12 verticals (Sigma GT-5, Sigma 40-XKR, etc.)

73,
Chuck  NI0C
   
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AA4PB
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« Reply #5 on: January 19, 2007, 06:25:54 PM »

There are companies who can push a pipe under the driveway without breaking the surface. I have no idea what it would cost.
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K5QED
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« Reply #6 on: January 20, 2007, 05:01:20 AM »

 -- There are companies who can push a pipe under the driveway without breaking the surface. I have no idea what it would cost --.
 _____________________________________________________
When the local telephone company recently laid a fiber optic network in my neighborhood, they used a horizontal boring rig to route the 2" plastic conduit under each section of driveway that they had to cross.

It required about a 1x2 foot access hole to be dug on each side of the driveway to feed in the drilling rod. This would probably not be a cost-effective solution for one conduit, but it was pretty slick.

Here in Texas, where lawn sprinkler systems are common, the local home improvement stores sell a type of "blaster" nozzle that attaches to your garden hose for routing sprinkler pipes under sidewalks and driveways. Seems to work fine in the clay soils here, where there are not a lot of buried rocks. Maybe this would do the trick for you.

73
Charles



 
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K9KJM
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« Reply #7 on: January 20, 2007, 07:52:19 PM »

You can rent or borrow a saw that will easily cut thru blacktop to make a larger "trench" for your pipe.
I would go with a pipe that is large enough for future use........  AND while the trench is open, Be sure to also lay in a nice heavy copper wire to bond your grounds together.
It would make little difference if your conduit pipe is plastic or steel. (Although there Might be a slight advantage for both RF and lightning protection if it is grounded steel)
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NI0C
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« Reply #8 on: January 21, 2007, 12:41:56 PM »

Thanks all for the comments and suggestions.  

73,
Chuck  NI0C
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KB5DPE
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« Reply #9 on: January 27, 2007, 10:22:50 AM »

Check out a "Ditch Witch".  I understand they are available at most tool rental places and, if I understand correctly, it will readily drill under a driveway as you need.  I have not used one as I moved from the house where I was going to use it, but I was told that it would do the job.
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WA2TNO
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« Reply #10 on: February 02, 2007, 08:30:47 AM »

I did this years ago, running coax through a galvanized pipe just below soil level to a 20 meter ground plane antenna, also supported by galvanized pipe (with the feed routed through the pipe).  It worked great.  One thing I speculated on, but never confirmed, was that the galvanized steel pipe acted as a choke to stray RF current on the outer surface of the coax cable... helping to keep stray RF out of the shack.  This was the best behaved antenna I ever had...in a rural environment...with no TVI or RFI.  

That's a big plus when the rest of the family and neighbors are watching weak signal TV and listening to weak signal AM and FM broadcasts.

WA2TNO
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KG6OMK
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« Reply #11 on: February 02, 2007, 06:06:29 PM »

I put pipe under a 15 foot wide concrete driveway without digging it up.  I dug a small hole one side about 18 inches deep and a couple feet square.  I got a short section of pipe, connect one end to a garden hose and hammered (5 pound sledge) the other end to make a pointed nosel.  It is not hard to push the pipe through dirt and if you put a 90 degree ell on before the hose you can use the 5 pound hammer to force the pipe.  After a few feet are in screw on another section of pipe.  After you have pushed enough pipe under the driveway only then dig the second hole.

Once you have this done try forcing a large diameter conduit.  A grey 2" PVC would be perfect
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NI0C
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« Reply #12 on: February 27, 2007, 03:15:17 PM »

I spent most of today working on my coax replacement project.  I routed new coax (Davis Buryflex) and a five conductor remote control cable (for a Force 12 Sigma GT-5 antenna) through a new piece of 3/4 PVC conduit across the slot I dug ten years ago in the driveway.  Much of the 125 ft coax run is neatly stashed in PVC near the ground tucked between the fence boards and the fence posts of my wooden privacy fence.  The cable goes to an MFJ remote switch controlled by a DC signal in the coax.  (Thanks a heap to Steve, WB2WIK, for suggesting this.)  

Thanks to all those who gave suggestions for getting a larger pipe buried under a driveway.  Unfortunately, in my case, this wouldn't work because I only have a couple of feet clearance on each side of the driveway (one side is near the brick wall of the attached garage; the other is near the aforementioned privacy fence).  

I think I'm going to enjoy the new installation for a long time, and the XYL is pleased because it looks so much better than the last installation.  

73 & thanks again to everyone for their hints and suggestions!

Chuck  NI0C    
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