New York World Trade Center three station, common antenna two-way repeater radio system

This paper descr ibes an indoor /outdoor an tenna s y s t e m t h a t serves t h e World Trade Center ' s th ree twoway r ad io s t a t ions , s imu l t aneous ly , each on d i f f e r e n t UHF channels . Each s t a t i o n p r o v i d e s : a ) b a s e t o p o r t ab le or mobi le communica t ions , b ) por tab le to por tab le r epea te r ope ra t ion and c ) one-way paging. The indoor s e c t i o n of the an tenna sys tem cons is t s of many branches of l eaky type an tenna t r ansmiss ion l i ne d i s t r ibu ted v i a c a r e f u l l y s e l e c t e d r u n s t h r o u g h o u t t h e s i x s u b t e r r a n i a n areas each t h e s i z e o f s e v e r a l f o o t b a l l f i e l d s . An assortment of transmitter combiners, receiver combiners and a q u a d r u p l e x e r c o u p l e s t h e s t a t i o n s t o t h e a n t e n n a system. Branching w a s accomplished using signal s p l i t ters and combiners. The ends of each branch were t e rmina ted wi th qua r t e r wave whip antennas mounted on ground planes to maximize signal condi t ions where down l i n e l o s s e s are t h e g r e a t e s t . An outdoor antenna serves t h e a b o v e t e r r a i n areas o f t h e b u i l d i n g s , t h e plaza, the surrounding s idewalks and s t reets ,