More Cable, Another Trench

I've dug trenches to bury a many long runs of cable. It isn't an easy job so I always add extra cable for future expansion. Since predictions about the future rarely work out, I inevitably require more cable than originally foreseen. Hence, more trenches.

Last week I dug a new trench to the 150' tower. When the trench was first dug in early 2018 (cables were on the surface for the tower's first winter) I laid down 4 runs of Heliax, 2 Cat5 control cables and cable for the prop pitch motor. 

Since then, I fully occupied the second control cable for the Beverage remote switch, which itself required a new trench. Last year I ran a new cable for the side mount TH6 rotator. I used almost every other control cable wire for the rotator and for the planned 10 meter stack switch.

One of the Heliax runs is ½" flex, which is not rated for burial. The price was right, I was in a rush, and despite the inappropriate burial it is still doing well after 4 years underground. Nevertheless, a replacement for it seems wise with the new trench prepared. Another Cat5 cable joined the LDF5-50A, and of course the 14/2 cable for the Ham-M rotator.

Refer to the earlier article and you'll notice how the routes of the two trenches differ. The photograph and way points guided the route of the new trench. I realized I might need a second trench when I dug the first. I planned the route of the first trench to easily accommodate this, the second trench.

It's a good thing it's just hay in the field since the plants are perennials and there is no need for the soil to be overturned for planting. Disturbing the soil to that degree is incompatible with buried cables and radials.

The first trench was dug with a small trencher (there's a pic in that earlier article) that I rented for a good price. Although it did a fine job, it was heavy, tiring to operate and it destroyed the surface vegetation. For the second big tower, the trencher was no longer available and I had time on my hands since the pandemic lock down had just begun (spring 2020). I picked up a shovel and pick axe and got busy. 

It was a lot of work, but not as much as I feared. That 170' long trench contains 3 Heliax runs, 2 control cables and a spare cable for a future side mount rotator. When the sod was replaced the hay quickly resumed its spring growth. Trenches dug by the trencher were barren of hay for the first season.

Although I am not shy of manual labour it is no easy choice to pick up a shovel rather than rent power equipment. However, my source dried up so that an economical rental was not available. At the time I believed that I would merely save money by digging the trench manually. The advantages were more than I anticipated:

• Low cost, if you have the time and endurance
• By using a spade the sod can be saved for rapid surface remediation
• There is no rush: work for an hour, rest and continue when you're ready, without regard to a ticking clock when you are using a rental
• Save the time of trencher transport (if you do it yourself), maintenance and cleaning and dragging it around the property
• Quiet and no exhaust fumes!
  

Despite not having timed myself, my guess is that the time investment is not very different for a shovel versus a trencher. Larger trenchers are self propelled, which would save time but those are more expensive. A shovel really isn't all that slow. If you are physically unable to do it, a trencher makes sense. 

There is no equivalent comparison for digging holes for tower bases since small backhoes make a mess. You'll likely need a wood form to pour the concrete. With a shovel you can make a "mud hole" that is far more precise and doesn't need a form. That can be well worth the effort of manual digging. You can also hire labourers to do it if you can't do it yourself. A trench does not need to be so precisely made.

In the trench picture at the top and the one at right (late fall of 2017), you can see water in the open trench. It inevitably rains before the trench can be back filled. Notice that the cables have been laid in the waterlogged hole regardless. 

If you feel leery about that, perhaps it's because you're not using cable that is rated for direct burial. Cable rated for burial will not be bothered by the open water or by saturated soil when it is buried. Spend a little more on the cable and you won't have to redo the job in a few years. That said, I often use unrated cable for low voltage AC and DC with an unblemished PVC jacket. So far so good, but don't expect miracles.

There are many stones below ground, both large and small. I remove the small stones but the big ones pose a problem. Most of the time I shift the trench several inches to route around them. Trenchers have enough power to remove many of the big stones that I wouldn't bother with when using a shovel.

There are other methods to bury single cables and wires where depth is not critical. In that first referenced article I demonstrated my mostly failed attempts to mechanically dig narrow and shallow trenches for radials. It did not make the job easier. It is better to lay radials on ground, pin them to the sod and let the vegetation grow to cover them. I have yet to snag a radial with the riding mower.

Another method is to slit the sod. I use the lawn edging tool shown at right. It takes very little time to cut a slot across the lawn. This is how I buried the burial grade cable for the new terrestrial wireless internet equipment that was mounted on the Trylon tower. It works best for narrow cables like Cat5/6/7 and RG6. It's impractical for thick cables and cable bundles.

Make the depth consistent since the half-round blade doesn't cut deep along its full width. Wiggle the tool to widen the slit. A length of thick steel (at least ¼") is used to push the cable into the slit. Keep a screwdriver or similar tool handy to cut the dirt missed with the edging tool. Do not bend or stress the cable by forcing it in. Clear the obstruction when you run into resistance.

One final job that I've been putting off for a long time is burying the multitude of cables from the stone wall surrounding the lawn to the Trylon tower. The weight of the cables adds up and it's becoming so heavy that I am uncertain how much more the aerial run with its steel messenger cable can withstand.

The biggest impediment is the 20 yd³ of topsoil in the way. It was there when I purchased the property and I gave it little thought at the time. A second problem is that the roots of the birch trees run close to the surface and they surround the wall. I've already had to deal with them on the outside of the wall -- the wall foundation isn't deep enough to block the roots. I cut the small roots and route around the larger ones.

The dirt pile can be moved with a small backhoe and I have a landscaping project that needs the soil. The birch tree roots are a more difficult challenge. It is unlikely that I'll deal with it this year. 

An alternative that I might choose is to increase the aerial run strength. A trench cannot solve all problems, and there is a benefit to having easy access to the cables for maintenance and station reconfiguration.