cal to long-term stability and trouble- free operation. The Tower and Erection Services provider must con- tribute to preservation of positive gas pressure at all times practical during installation. The following are minimum requirements and the responsibility of the service provider on-site supervisor: The antenna will be under pressure when it arrives on site. The antenna input terminal will include a gas stop. The gas stop must remain in place until the antenna is safely mounted on the tower and the vertical transmission line and tower top elbow complex are ready for connection to the antenna. PRACTICAL IP AND TELECOM FOR BROADCAST ENGINEERING AND OPERATIONS The transmission line must be assembled from the ground up. The horizontal line will be mounted in a three-point spring hanger suspension arrangement. The vertical line will be mounted with a minimum of two spring hangers attached to mounting brackets on tower members. At the end of each working day or upon work stoppage because of weather, the in-place line will have a cap provided for the purpose of sealing the transmission line. This cap is to be installed anytime work is stopped for more than 2 hours. Upon completion of installation of the transmission line and before connection to the tower top elbow complex, a precision terminating load will be attached to the line. The line will be purged with dry air or nitrogen whereby the termination load is not tightened gas tight SO as to permit "bleeding" of dry air equal to three times the capacity of the line. Usually this can be done over- night or within a few hours. The Passive Transmission Systems supplier representative will make measurements on the line. When the tower-top elbow complex has been installed and con- nected to the vertical line, the precision load will be moved to the antenna side of the complex, the system pressurized again, and measurements made. After the measurements are complete and the antenna is in place, the gas stop will be removed and the final connection of all components made