Bird Technologies 4331 - Manual (Page 28)

and detection of reflected power is possible down to about 0.1 watt.
Caution is necessary in the above method and preferably it should not be
used with element ranges differing by more than 10 to 1 although 25 to 1
can be used with extreme caution. With elements available having ranges
down to one watt or less full scale, this method is usable with medium and
low power transmitters.
Measurement And Monitoring of Transmitter Power
The Thruline Wattmeter is useful for the continuous monitoring of transmit-
ter output and is also helpful for the continuous monitoring of reflected power,
for instance in checking intermittent antenna or line faults.
Like diode devices in general, the Model 43 indicates the carrier component
on amplitude modulation, with very little response to side band components
added by modulation.
Testing of Lines, Connectors, Filters, Etc.
The Thruline Wattmeter is highly useful for this purpose, and may be
employed in several ways.
1. VSWR (Insertion) or φ (Insertion) may be measured with
the line terminated in a good Termaline Load Resistor.
2. Attenuation (power lost by heat in the line) as well as
VSWR (Insertion) and φ (Insertion) may be measured by
inserting the unknown line between Thruline Wattmeter
units, or between two RF line sections using only one me-
ter and one set of elements (the end of the line to be ter-
minated in a good load resistor). This method applies
also to insertion between a Thruline Wattmeter and a
Termaline Absorption Wattmeter. Very small values of at-
φ = = =
0 1
80
0 00125 0 1% 1 06
.
. . . or close to or to roughly p
Bird Model 43 Wattmeter
14