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CPI Satcom Division equipment usually is related to amplification of a RF signal from an external
source. Even if a source is not connected to the amplifier you are working with, there are
situations where the amplifier can go into a self-induced mode and generate high levels of RF
energy. This condition can exist if the unit is operated with high voltage ON and without proper
termination on the input and output of the amplifier.
CAUTION! PROTECT YOURSELF AND THOSE AROUND YOU FROM UNWANTED RF
EXPOSURE. ALWAYS TERMINATE THE AMPLIFIER INPUT AND OUTPUT WITH A
RF DUMMY LOAD BEFORE YOU TURN THE HIGH VOLTAGE ON. THIS WILL
REDUCE THE CHANCES OF OSCILLATION DUE TO INTERNAL AMPLIFIER NOISE.
Microwave Discussion
Limit exposure to microwave radiation to prevent unwanted biological effects. There are other
effects that can lead to problems if you are careless in operating or servicing microwave
equipment.
The permissible levels are quite low in comparison to the power levels of the
amplifiers built by CPI (e.g., less than 10 milliwatts vs. 20 to 10,000 Watts delivered by different
units)
Local radiation levels can be detected with the proper equipment. The permissible levels are
currently being studied by a number of organizations.
established a dosage rate of 10mw/cm. Sq. Recently the permissible level has been reduced to
1mw/cm. sq. in the United States, as has been the case in several European countries.
General Microwave Guidelines
The purpose of these guidelines is to provide practical approaches to control unwanted
microwave energy associated with the operation and servicing of CPI Satcom Division equipment.
The following approaches are effective in both laboratory or field environments:
a. Always terminate the output waveguide or coaxial connector with a dummy RF load
(capable of dissipating full CW RF power). Similarly, terminate the input to avoid the
possibility of the amplifier being driven by stray leakage signals.
terminations prior to applying prime power to the amplifier. This procedure prevents self-
oscillation and irradiation of the local equipment.
b. Do not look into the output port of the powered RF amplifier. Treat the powered amplifier
as though it is a loaded gun. Your eyes are particularly vulnerable parts of your body.
c. Shut off the unit if you are trying to locate a RF leak. As noted earlier, the levels of concern
are very low. Examine the physical unit with the high voltage OFF. If you have to survey the
RF runs with the power ON to find the leaky joint or component, start by testing the system
with low RF input and a radiation meter.
If the microwave radiation exceeds 0.5mw/cm. sq., shut OFF the high power voltage and consult
your supervisor. Work quickly (not at a panic pace) to minimize the dose level. The dose you get
is directly proportional to the power level and the time you are exposed. Exposure to microwave
radiation can induce both thermal and non-thermal biological effects, especially with the eyes.
D
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REPRODUCTION OR RELEASE WITHOUT EXPRESS PERMISSION IS STRICTLY PROHIBITED
THIS DOCUMENT IS THE PROPERTY OF COMMUNICATIONS & POWER INDUSTRIES.
In the past the U.S. Safety Codes
Incorporate the
CHPA SERIES
S-5
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