Tower Completed, Ready to Raise

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Repainting To Control Summer Heat

Temperatures of 104 degrees Fahrenheit were common inside the shed when outside temps were still only 85.  This had to be improved.  Step one was to cut two 6″ circular vents into one gable and add a solar powered fan.  No noticeable improvement.  Step two was to cut in a second vent in the opposite gable.  Same result.  Third step was to cut in a 8″ X 16″ vent midway up the north wall.  Same result.  Fourth step was to paint the shed white.  This helped.  Inside and outside temps since have been nearly the same.  The cute barn red shed is now almost ugly white.  But it’s cool inside.

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Why the concern? We were worried more about the batteries than the equipment.  The electronic equipment was still within specified operating range at 104.  Sources say batteries, on the other hand, can exhibit thermal runaway (catch fire) at 122 degrees.  Summer’s highest temperatures hadn’t even arrived yet.

Web-based Coax Switch

Another box checked on the station upgrade list.  The web-based coax switch enables selecting one of 5 antennas remotely over the Internet.  It is a Remote Rig Model 1289 Antenna Switch.

In this picture we have three antennas installed and room for two more.

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Tower Progesss

This tower will be 60 feet tall, is made of aluminum, and will tilt over to allow work to be done on the antenna.  Today the concrete was poured for the 4′ X 4′ X 4′ tower base, a significant milestone.

In this picture I am proudly holding down a pile of dirt with my left foot.

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Once the concrete cures the next step will be to tilt over the section shown here and bolt together the rest of the tower one section at a time.   Then the antenna, the rotor, the cables, the tilting fixture, and finally the grounding will be completed.  Thanks to KC0RF once again for the help today.  John easily won the prize for  “most stylish dresser”.

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Thoughts on Grounding

Ground the main strike at the tower base.  Worry about protecting your equipment (and people) from what’s left over.

My tower and my equipment shack are 100 feet apart.  Bonding the two would be fruitless because of the inductance of the bonding conductor.   So don’t bond when the two are that far apart.  Ground the tower.   Ground the shed.  Worry the most about protecting the equipment in the shed.

Accomplish the first part by putting a ufer ground* in the concrete base and spacing ground rods around the tower, all bonded in a wagon wheel ring.  That should divert just about any lightning strike.  Do not bond to the equipment shed when it’s 100 feet away.

At the shed install spaced ground rods and bond them in a wagon wheel ring.  Install protection on all cables at their entry point, coax, Internet, power, rotator, etc. and bond together.

 

 

*The Ufer Ground is an electrical earth grounding method developed during World War II. It uses a concrete-encased electrode to improve grounding in dry areas. The technique is used in construction of concrete foundations.   –Wikipedia

More…

The principle of the Ufer ground is simple, it is very effective and inexpensive to install during new construction. The Ufer ground takes good advantage of concrete’s properties. Concrete absorbs moisture quickly and loses moisture very slowly. The mineral properties of concrete (lime and others) and their inherent pH means concrete has a supply of ions and free electrons to conduct current. The soil around concrete becomes “doped” by the concrete, as a result, the pH of the soil rises and reduces what would normally be 1000 ohm soil conditions (hard to get a good ground). The moisture present, (concrete gives up moisture very slowly), in combination with the “doped” soil, make a good conductor for electrical energy or lightning currents.   —psihq.com

Cable entrance cabinet with single point ground plate and protectors.  All cables pass through this box before entering the shed in an attempt to stop all strike current from going inside.  The copper plate is bonded to a ground rod and eventually a ground ring around the shed with spaced ground rods.

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June 28, 2017: John picked up 100 feet of No. 2 Solid Copper today to serve as the ground ring.  Yay.

 

Tower Base Ready For Concrete

Finally got to this point  (see bullet point 4, below).  It seemed like the digging would never end, but it did and now the hole is ready for the concrete pour.

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One of the rebars is allowed to protrude upwards and will be bonded to the tower along with ground rods to make up the ground system. The rebar is the “ufer ground”.