Western Electric 407A-4, Instruction Manual

Page: 64 / 136

An
anti-s ing as sembly cons i sting of R2D-L9D is connected
in the plate lead of V2D. A s imilar cir cuit cons isting of
R2E-L7E is connected in the plate lead of VlE.
Plate blocking condens ers C7D a.re used for V2D, an d
blocking c ondens ers C 7E for VlE. C 9D and C 9E a.re filB411ent
by-pass condens ers .
The antenna current is indicated by ammeter M3E which
operates in parallel with ammeter M7A from the thermocouple
TC 3A, and which is provided with a. calibrating res istor R6E.
The individual filament voltages on the tub es are in­
dic ated by M7D and M7E.
Circuit
Antenna Equipment
The output of the 407A-4 Equipment is us uall y fe d to
one or more tower radiators through concentric transmis s ion
l ines and suitable coupling circuit s . The coupling equip­
ment and its arrangement are specifie d individuall y for each
installati on, and are not describ e d herein. However, the
antenna installati on should b e complete and the coupling
equipment adjusted pri or to adjustment of the output s tage
of the transmitter, s o as to provide a suitable l oad for the
latter.
Harmonic Suppress ion Line
The harmonic shunt line supplied with this equipment
should have an e lectrical length of exactly one quarter
wave , with its inner and outer condu ctors connected to­
gether at the far end. When its length is correctly ad­
justed, it will have no appreciab le effect at the funda­
mental frequenc y, but will b e practically a short circuit
on the transmitter output for all even harmonics .
Experience
has
shown that for a. given frequency the
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