Antennas at NRX

20 Meter Stack

This is the first of the two 150 towers at NRX. The antennas are three 4 element 20 meter yagis fed in phase with a WXB Stackmatch. The boom length is 36 feet. The design was taken from ON4UN's Yagi Design Software library. They are fed with T-matches. The rotator which is at the base of the tower is powered by a 115 volt, 1/4 horsepower motor,  which turns the entire tower at about one RPM. The rotor also includes a rotating coax feed through and there are no end stops required.  The guy anchors are set back 200 feet. The tower is from a defunct broadcast station. They are manufactured by Utility Corp in Oklahoma City. All but the top section are 20 foot long. They weigh 325 pounds each. The guy rings were copied from a design by NNI.  Each ring congtains six track rollers (needle bearings), three in each axis. The top two guy sets are 5/16 inc;h in diameter and the bottow set are 1/4 inch in diambeter. All are EHS steel broken up with strain insulators to render them non-resonant at 14 mHz.  The feed line to the tower is 1-5/8 inch heliax. This tower and antennas was erected with the help of WB8ZRL and WAWL.

 

10/15 Meter Stacks

This is the second of the two 150 towers at NRX. The 10 meter stack consists of three 6 element Yagis having 35 foot booms. The 15 meter stack consists of three 5  element Yagis on 35 foot booms. Both stacks are fed in phase with T-matches and WXB Stackmatches. The design was taken from ON4UN's Yagi Design Software library. The rotator which is at the base of the tower is powered by a 115 volt, 1/4 horsepower motor,  which turns the entire tower at about one RPM. The rotor also includes a rotating coax feed through and there are no end stops required.  The guy anchors are set back 200 feet. The tower is from a defunct broadcast station. It was manufactured by Utility Tower Corp in Oklahoma City. They are model 340 and all but the top section are 20 foot long and weigh 325 pounds each. The guy rings were copied from a design by NNI.  Each ring congtains six track rollers (needle bearings), three in each axis. The top two guy sets are 5/16 inc;h in diameter and the bottow set are 1/4 inch in diambeter. All are EHS steel broken up with strain insulators to render them non-resonant at 14 mHz.  The feed line to the tower is 1-5/8 inch heliax. This tower and antennas was erected with the help of my XYL KEGQ.

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