Stop filter for VHF band - has adjustable centre tube in outer semicircular housing to form variable capacitor

摘要

The UHF stop filter tunable by using an adjustable capacitor, employing a parallel resonant circuit and whose inductance acts as a surge resistance. The design uses relatively large mass conductors instead of wires. The main conductor (3) and the decoupling conductor (9) are formed of stout material in cylindrical or half cylindrical form, both are joined to inputs at the end by a flexible connection (10), and wired away to the inner (12) of a coaxial cable (13). The circuit parameters are altered by moving the two input connections (12, 13) together or apart along the guide rail on the backing plate (2) so that the one conductor (3) as a semi-cylindrical surround, interacts with the tube conductor (9) moving within it. The end connections (10) to the conductors (3, 9) of the circuit are wired through the conducting support plate (2) by means of insulating glass grommets (11).