GatesAir Inc. CZF Manual De Usuario
APEX
™
Exciter Incorporating FLO
™
Technology
Maintenance and Troubleshooting
Exciter Maintenance
Page: 5-6
888-2604-001
03/08/07
WARNING: Disconnect primary power prior to servicing.
5.1.2
Measuring PLL Board Frequencies
Channel center frequency accuracy is directly dependant on the accuracy of the 1st and 2nd
local oscillators (LOs) in the PLL board, which get their reference from the 10 MHz
reference oscillator. If a large channel center frequency error exists, first check the
frequency and frequency offset entries on the exciter setup screen, and then check the PLL
status screen (second of four IF & RF processing status screens) for faults. If one or more
faults appear on this screen, refer to Section 5.8.1 on page 5-19 for additional trouble-
shooting information.
local oscillators (LOs) in the PLL board, which get their reference from the 10 MHz
reference oscillator. If a large channel center frequency error exists, first check the
frequency and frequency offset entries on the exciter setup screen, and then check the PLL
status screen (second of four IF & RF processing status screens) for faults. If one or more
faults appear on this screen, refer to Section 5.8.1 on page 5-19 for additional trouble-
shooting information.
Channel center frequency error can be caused by several factors, which are listed below.
• Error in exciter setup screen frequency or frequency offset. These entries set the chan-
nel center frequency and frequency offset (if required) from the normal channel cen-
ter frequency.
ter frequency.
• 1st and 2nd local oscillator frequency errors caused by internal 10 MHz reference os-
cillator errors.
• 1st or 2nd local oscillator frequency errors caused by a faulty PLL board.
5.1.2.1
Measuring Center Channel Frequency
A special procedure which removes all transmitted data leaves only one center channel
carrier. This allows the channel center frequency to be directly measured at the exciter
output. A suitable frequency counter will be needed. This is not a normal operating
procedure.
carrier. This allows the channel center frequency to be directly measured at the exciter
output. A suitable frequency counter will be needed. This is not a normal operating
procedure.
Caution
Do not use this procedure while exciter is providing drive to an op-
erating transmitter. The single carrier operation will cause the trans-
mitter output to rise sharply and may cause overloads or even
equipment damage.
erating transmitter. The single carrier operation will cause the trans-
mitter output to rise sharply and may cause overloads or even
equipment damage.
Note
The exciter is locked to a GPA 1PPS reference. Its output is accu-
rate to a fraction of a hertz. The frequency counter must also oper-
ate from a GPS reference to enable it to measure frequency with the
required accuracy.
rate to a fraction of a hertz. The frequency counter must also oper-
ate from a GPS reference to enable it to measure frequency with the
required accuracy.
The frequency measurement procedure is as follows.
1
Power down the transmitter before connecting or disconnecting any cables.
2
Remove the exciter drive cable from the PA. This prevents PA overdrive or damage
during single frequency operation.
during single frequency operation.
3
Pad the exciter output sufficiently to prevent frequency counter overdrive or damage,
then connect it to the frequency counter.
then connect it to the frequency counter.
4
Connect a male-female DB-9 straight-through cable from Com 1 on your computer to
the RS232 connector on the front or rear panel of the APEX FLO exciter.
the RS232 connector on the front or rear panel of the APEX FLO exciter.
5
Open Tera Term Pro on the computer.
6
Select “Setup > Serial port”.