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LOW POWER OUTPUT:
The most common amplifier problem is low power output. If the installation test shown in
Section 3 is run the power input/output specification on the nameplate should be met,
especially when working into a dummy load, since this is essentially the test run at the
factory.
The most common amplifier problem is low power output. If the installation test shown in
Section 3 is run the power input/output specification on the nameplate should be met,
especially when working into a dummy load, since this is essentially the test run at the
factory.
If working with BIRD wattmeters, remember that the power output reading is specified at
+/-5% of full scale. In other words, a wattmeter with a 100w element gives readings of
+/-5 watts when the wattmeter is reading full scale. Mid-scale readings have much
lower accuracy. Always use an element closest to full scale for maximum accuracy.
Treat your element with extreme care. Dirty or dropped elements always read low.
+/-5% of full scale. In other words, a wattmeter with a 100w element gives readings of
+/-5 watts when the wattmeter is reading full scale. Mid-scale readings have much
lower accuracy. Always use an element closest to full scale for maximum accuracy.
Treat your element with extreme care. Dirty or dropped elements always read low.
Make sure that your power supply is adjusted to 28 volts. The input/output powers
specified on the nameplate were taken at 28 volts. Measure the voltage at the amplifier
terminals to be sure all the DC connections are tight and that the amplifier is seeing 28
volts during operation. Check the manufacturer's ratings to be sure the CONTINUOUS
rating of the power supply is sufficient to power the amplifier. If the power supply is
slumping, the amplifier output will go down with the voltage.
specified on the nameplate were taken at 28 volts. Measure the voltage at the amplifier
terminals to be sure all the DC connections are tight and that the amplifier is seeing 28
volts during operation. Check the manufacturer's ratings to be sure the CONTINUOUS
rating of the power supply is sufficient to power the amplifier. If the power supply is
slumping, the amplifier output will go down with the voltage.
Look at the drive power while the amplifier is operating. Many exciters will put out
different powers into even slightly different loads. Low drive power will produce low
output power. Do not assume that your exciter output power with the exciter running
into a dummy load will be the same as when the exciter is running the amplifier. A
strong RF field can sometimes cause an exciters to increase or decrease power as well
as go spurious. In-band spurious signals maybe amplified. The change in signal level
will show up on the input wattmeter. RF fields can also cause linear power supplies to
fall out of regulation. This should be seen on a voltmeter (CAUTION: RF can effect
digital voltmeters, too.)
different powers into even slightly different loads. Low drive power will produce low
output power. Do not assume that your exciter output power with the exciter running
into a dummy load will be the same as when the exciter is running the amplifier. A
strong RF field can sometimes cause an exciters to increase or decrease power as well
as go spurious. In-band spurious signals maybe amplified. The change in signal level
will show up on the input wattmeter. RF fields can also cause linear power supplies to
fall out of regulation. This should be seen on a voltmeter (CAUTION: RF can effect
digital voltmeters, too.)
Low (or high) output powers can be the result of a high output SWR. Carefully check
your loads and connecting cables.
your loads and connecting cables.
NO OUTPUT POWER:
After checking the above items, be aware that there is protection circuitry. Check with
the factory if you suspect that the internal protection has or is operating. As a rule, if the
front panel light and fan are operating and output is zero, the SWR circuit has operated
(usually with an audible click upon key-up.) If the SWR protection were operating, you
would notice the output wattmeter "jump" briefly upon key up and then return to zero.
After checking the above items, be aware that there is protection circuitry. Check with
the factory if you suspect that the internal protection has or is operating. As a rule, if the
front panel light and fan are operating and output is zero, the SWR circuit has operated
(usually with an audible click upon key-up.) If the SWR protection were operating, you
would notice the output wattmeter "jump" briefly upon key up and then return to zero.
If the front panel light does not light, either the input drive isn't high enough to trigger the
amplifier on or the amplifier has disconnected itself from DC power. The amplifier will
reset itself when it cools down. (Some power supplies will "spring up" in voltage when a
heavy load is released and settle down to normal after 100-200 milliseconds. This can
damage an amplifier.)
amplifier on or the amplifier has disconnected itself from DC power. The amplifier will
reset itself when it cools down. (Some power supplies will "spring up" in voltage when a
heavy load is released and settle down to normal after 100-200 milliseconds. This can
damage an amplifier.)
If all else fails, give us a call. We'll be glad to help!