Critter Protection for the 80 Meter Array

This is not the first time I've talked about critter damage to my 80 meter vertical yagi. The cables, wires and enclosures are close to the ground and, for some reason I don't understand, deer appear to enjoy chewing on all of it. At least, I think it's the deer, going from the marks of mastication on plastic components. Maybe they're curious or bored. Regardless of the reason, the unwanted repair work is aggravating.

The bouts of damage this fall motivated me to take preventive measures that I've been avoiding. There are temporary and permanent fixes, with the temporary ones to be changed to permanent when I have more time. I am very busy this month with other projects.

I'll step through the work I've done to give an idea of what I'm dealing with. Although one item is for safety and not critter protection, I'll mention it anyway. Let's cover it first.

All turnbuckles should have safety cables. The cables tie the guy to the ground anchor. If the turnbuckle fails the cable prevents the tower from collapsing. The tower in the 80 meter array is the driven element and it supports the parasitic wire elements. 

The guy tension is quite low, just enough to keep the tower stable for climbing. I've been meaning to get this job done, and after 3 years its time has come.

One disadvantage of safeties is that the turnbuckle cannot be adjusted without temporarily removing the safety. This is difficult on the big towers since the safeties are ¼" EHS. It is a struggle to route the tough, springy stuff through the eyelets and bodies of the 4 turnbuckles without kinking the cable. It is also a potentially dangerous task. Bent EHS that slips out of your grip springs back forcefully and can do serious injury. The ⅛" aircraft cable used for the 80 meter tower turnbuckles is far easier to work with.

The parasitic elements are sloped T-shaped wires per the original K3LR design. Both ends of the sloping wire (top of the T) are supported by ropes: one to the top of the driven element and one to the ground anchor. Tension on the ropes keeps the element in place.

Deer enjoy chewing rope. That was a surprise to me, but I'm no expert on deer behaviour. Cutting a support rope disables two directions of the array. The other two directions are impaired since all the parasitic elements will sag when one rope is cut. It is an easy repair, but an aggravating one to have to do (again).

The solution is the same as it is for towers guyed with non-metallic cable such as Phillystran. The bottom of the guy is steel and connects to the main guy at a height that is sufficient to avoid accidental damage from mowers, walkers, tractors and critters. Due to the slope of the element the steel cable needs to be at least 10' (3 m) long to be safe from curious deer.

The cables are 3/16" aircraft cable since it was loitering in my junk box with no other obvious use. In this specific application almost any size of steel will do. I did not cut the ropes to size after installing the steel cables in case I need them in the future. The deer are free to chew these trailing ends if they want. The dangling extra rope was attached to the steel cable after the picture was taken.

Protecting the exposed control cables, antenna wires and enclosures at the 5 elements requires cages. The cages must be non-conductive, anchored to the ground, allow rain and snow to drain, not encourage insects to shelter there and, finally, discourage curious animals. I have a few candidate designs in mind that I can build with material on hand.

The project is not difficult except that time is needed, and right now that is in short supply. As a temporary measure I did something that was fast, cheap and ugly. I wrapped all 5 elements in plastic sheet (yes, that includes the tower base!).  The black plastic is resistant to UV from my experience using it in other temporary weatherproofing jobs.

It is obviously a poor physical barrier since any animal can easily tear through it. What I am betting on is a visual deterrent since deer are not too smart. If they see a large black blob they will likely leave it alone. What they can't see probably won't attract their attention.

Hopefully this will suffice a few months until I can build a permanent solution. The plastic wrap is easy to remove should antenna repairs be required. It is held together with black electrical tape that is easy to peel off and then back on. If it tears, well, I have an endless supply of plastic sheet.

They have never chewed on exposed Heliax, which is exposed in numerous places and is much thicker than the cables and wires they have damaged. Apparently size matters, and that is why I am guessing the "big black blob" solution might work.

Speaking of Heliax, there is one more job to be done. Although no animal has attacked the many runs of Heliax exposed at ground level, in my enthusiasm I decided to protect the exposed Heliax to the 80 meter array. The underground run of LDF4 from the electronics at the tower base is only to the edge of the radial field. It connects to a long run of LDF5 that is mostly buried but overground near the junction due to trees roots and rocks.

I wrapped the exposed junction in chicken wire. Steel discourages critters, so even though the plastic outer layer can be touched through the mesh it is unlikely to suffer bites or chewing. Rodents might but they have yet to touch any wires and cables that are on the ground or shallowly buried.

Now I cross my fingers and hope that these measures will provide lasting protection. Clearly there is more work to be done, and it is a good project during winter when tower work is suspended. 

As an aside, here is a hint of where my time is being spent. Notice that the 150' tower has no antennas on top. The TH7 and experimental 40 meter dipole were taken down last week with the assistance of several friends. 

The TH7 will remain on the ground this winter and may be permanently retired. The 40 meter dipole was inspected to see that it suffered no stress fractures or other problems. It passed inspection so I am continuing with the element design to make the director and reflector for the 3-element yagi I am building.

The 40 meter yagi in particular is responsible for my lack of time for smaller projects this fall. I will soon be raising the 10 meter yagis onto this tower (one fixed, one rotatable) in preparation for the big 40 meter lift. More about these and other projects in future articles.