Bird Electronic 4314B, Operation Manual

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Bird Technologies
16
Making Low Reflection Readings
It is sometimes desirable to make more accurate low reflection read-
ings. This can be done using a more sensitive element, provided that
care is taken to prevent application of high forward power to the low-
power element. This procedure is limited to use with higher power
transmitters only.
1. Measure watts forward, using the proper Plug-In Element.
2. Reverse the arrow direction of the element to determine the gen-
eral level of reflected power.
3. Remove the Plug-In Element.
4. Insert a lower power element which has a maximum rating of
more than the reflected power indicated in the first measurement.
5. Isert the element, carefully, so that it reads reflected power only.
6. Read the reflected power on the meter in the usual manner.
Note:
When using the two-element method of reading low
reflected power, it is not recommend using a pair of elements
which has a full scale power differential of greater than 10 to 1.
Testing Lines, Connectors, Filters & Related Components
Lines, connectors, filters, and related components can be tested using
the Thruline Wattmeter. The method of testing depends upon the cir-
cumstances involved for any particular test. Some of these tests are
listed below:
The standing wave ratio or the reflected-power to forward-power ratio
of a line can be determined by terminating the line with a good load
resistor, such as a Bird Termaline Load Resistor. Proceed as described
under determining VSWR. Low reflected power may be measured as
described above.
Line attenuation (power lost as heat in the line) can be determined by
inserting the line of unknown value between two Thruline Wattmeters.
The end of the line must
be terminated by a load resistor. The attenua-
tion of the line can be determined by comparing readings made at the
two ends. Allowances must be made for normal instrument error where
very small values of attenuation are involved. Some correction may be
made by direct rigid connection of the Thruline Wattmeters.
CAUTION
When making low reflection readings using a more sensitive element,
take care to insert the element so that it senses reflected power only.
Do not rotate the element in the socket so that it is subjected to
forward power. This can result in damage to the Plug-In Element, the
microammeter, or both.