Technical ยป K0AL Antenna and Tower Project
 
K0AL Antenna and Tower Project PDF Print E-mail
Written by Al Culbert, K0AL   


 Al Culbert - K0AL, recently purchased a second QTH to get away from HOA restrictions.  The property would easily support a good sized tower so during the summer of 2015 assembly began.  The following describes the technical aspects of tower assembly and the antenna system.


The tower has a base about 4 feet square by 3 feet deep and then a center section about 2 feet square
 which goes down to ground water at 6 feet.  It has 1.25 cubic yards of concrete which was reinforced
with fiberglass and pumped in place with a trailer mounted pumper. 

The tower base has a 4 foot section of tower buried in the concrete as well as #4 re-rods in the upper base section.

K0AL Tower 01


The tower is 80 feet of Rohn 45G.  It is grounded with three 8 foot ground rods tied to each tower leg and
 the legs are connected to the ground rods with solid copper strapping.

K0AL Tower 02


The three guys are elevated about 6 feet above ground to avoid personnel hazard while mowing or
other  outside activity. These guy posts were fabricated from heavy walled 6 inch square steel tubing
 which had been galvanized.  Each of the guy points has about 1.25 cubic yards of concrete which was
reinforced with fiberglass.

K0AL Tower 03


The tower is guyed according to the manufacturer's specifications for 130 m.p.h. winds using a
combination of 1/4" EHS steel cable and 6700 pound rated PHILLYSTRAN.   The guy posts were
also "slugged" with concrete.

K0AL Tower 04


Each section of the Rohn Tower was hoisted up and installed in place.

K0AL Tower 06


All aerial work was done by Ron LeBrun of Zephyr Hills, FL. Ron is a very experienced tower man and has
 the experience and equipment to make this work seem like child's play - which it most definitely is NOT.

K0AL Tower 07



The tower is topped off with a top plate which mounts a thrust bearing and about 2 feet below that is
another thrust bearing, thus there is minimal weight bearing on the Hy-Gain "Tailtwister" rotator. 


K0AL Tower 07A l



This is where a Tower man starts to earn his keep

K0AL Tower 08


A pulley system was set up to hoist the antennas to the top of the tower.

K0AL Tower 12



Antenna at top of tower.  Just needs to be installed.  The upper antenna is a rotatable 40 meter dipole
manufactured by JK Antennas.

K0AL Tower 13


The lower antenna is an OPTI-BEAM 9-5 which is manufactured in Germany. It has 9 elements and
covers the 5 bands 20 through 10 meters.  The mast is a 22 foot length of galvanized heavy wall
4130 chrome-moly tubing.

K0AL Tower 14


On a stainless steel angle bolted to two legs of the tower at the 75 foot
level is suspended a 30 meter dipole.  There is also a marine pulley mounted
 to this arm which can be used to raise experimental antennas, such as a
 delta loop or an inverted "L" for 160 meters.

K0AL Tower 15 l


 
All done.  Time to make some contacts.

K0AL Tower 17


After much deliberation and looking at various manufacturer's samples at the Dayton Hamfest,
I opted for "Bury Flex" coaxial cable from RF Davis Company. The rotor control was the
heaviest that Galen (WB0W) handles. All coaxial cable shields are grounded at or near the
top of the tower.

At the base of the tower is mounted a weather-tite PVC box I picked up at the January
Tampa ARC swapmeet which contains the PolyPhaser lightning protection devices for
the coaxial cables and rotor control cable.

The balun choke for the OPTI-BEAM and the 30 meter dipole were constructed by me using
using type 31 ferrite toroids. The 40 meter rotatable dipole uses a Balun Designs
model 1115d which was developed by Balun Designs specifically for this antenna.

How do they play?  I have swept them with my analyzer and they all  show resonance
and swr readings equal or better than claimed.