Bird Technologies 4314B - Manual (Page 13)

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Chapter 1 Introduction
Purpose and Function
The Model 4314B Thruline Wattmeter is an insertion- type RF wattmeter
designed to measure power flow and load match in 50 ohm coaxial transmission
lines. It is intended for use on CW, AM, FM, SSB, TV, and pulse signals only.
Description
The Model 4314B Thruline Wattmeter is a portable unit contained in a die cast
aluminum housing. The unit is equipped with a plastic strap for carrying, four
rubber shock feet on the base, and four rubber bumpers on the back which
allow the unit to stand vertical or lie flat in a horizontal position when used. For
additional protection, the microammeter is specially shock mounted. A slotted
screw is provided on the lower front face of the meter for zeroing the pointer.
The RF line section face below the meter protrudes slightly from the wattmeter
housing with the Plug-In Element socket in the center. The circuit module is
mounted on the line section inside the housing. It has an attached phosphor
bronze spring contact finger, which protrudes through a lateral hole and into the
Plug-In Element socket on the RF line section. The finger has a button on its end
which makes connection with the contacts of the Plug-in Element. The silver-
plated brass RF line section is precision made to provide the best possible
impedance match to the coaxial RF transmission line in which the wattmeter is
inserted. At each end of the line section are Bird Quick-Change type RF connec-
tors, which may be quickly interchanged with any other Bird “QC” connectors.
Performance Characteristics and Capabilities
To make measurements, insert a Plug-In Element into the line section socket and
rotate it to either stop. Point the element arrow in the source to load direction of
power flow and the meter will display a reading of forward power. Rotate the ele-
ment so that the arrow is pointed in the opposite direction to obtain a reflected
power reading. With known values of forward and reflected power the load match
can now be determined by calculating the VSWR or by using the graphs supplied in
this manual (Figure 5 on page 14 and Figure 6 on page 15).
Setting the front panel toggle switch to peak mode gives the wattmeter the
capability of indicating peak pulse or envelope power.