APEX™ Exciter Incorporating FLO™ Technology
Navigating the LCD Display Screens Details of the System Setup Screens
Page: 3-36 888-2604-001 03/08/07
WARNING: Disconnect primary power prior to servicing.
After the 1PPS Mute Delay loss time out has expired, the exciter will mute and the RF
output will be zero. The 1PPS Mute Delay range is programable from 0 to 2000 min-
utes. This setting is found (or changed) in the Main Screen > Setup > FLO FPGA >
FPGA Configure 2/5.
Internal is an alternate mode. If used, a GPS antenna signal input at the ANT rear
panel connector is required.
Loss of the GPS antenna signal will cause no noticeable effects.
• Frequency: Enter the center frequency (whole megahertz) for the desired transmitting
channel. For example 702 MHz, not 701.9 MHz or 702.1 Mhz
• Freq. Offset: This entry can move the center frequency up to +/- 50 kHz away from
the center frequency entered above. Enter the desired frequency offset in hertz. The
maximum limits which can be entered as a frequency offset is +/-50000 Hz.
Note
The frequency and frequency offset boxes will be greyed out (and
unattainable) if the diagnostic setup feature is locked. Instructions
to lock or unlock the diagnostics setup is found in Section 3.6.8.2,
Diagnostics Setup (Locked or Unlocked), on page 3-54.
• Transmitter: Select the transmitter type from the display that appears. Choices are
presently limited to Atlas ATSC (Harris Atlas series UHF digital transmitters).
• Waveguide Type: For UHF frequencies, enter the type of waveguide used between
the HPF and the antenna.
Selecting a type (and length) of waveguide allows RTAC to pre correct for waveguide
group delay. Selecting None provides no waveguide group delay precorrection.
If the wrong type of waveguide is selected for the operating frequency, no group de-
lay precorrection will be applied.
Available choices are:
None
WR1800, rectangular, for 470 through 605 MHz
WR1500, rectangular, for 506 through 728 MHz
WR1150, rectangular, for 662 through 806 MHz
GLW1750, circular, for 470 through 506 and 530 MHz through 638 MHz
GLW1700, circular, for 506 through 530 MHz
GLW1500, circular, for 620 through 722 MHz
GLW1350, circular, for 722 through 806 MHz
• Waveguide Length: Enter the length of waveguide (up to 2000 feet) used between the
HPF and the antenna. Length is needed, in addition to selecting waveguide type, to al-
low RTAC to pre correct for waveguide group delay.
• The modulator occasionally generates peaks as high as 18 dB above the average out-
put level. Max. Mod. Crest Factor represents the maximum peak power output limit
from the exciter, which limits the peak to average power ratio of the exciter output
signal. The range is 6 to 13 dB. For example, if the maximum modulation crest factor
is set to 10 dB, the exciter will clip any peaks which are greater than 10 dB above the
average output power level.
If set too low, it will raise the adjacent channel inter modulation product level, and
limit the correcting ability of the non-linear RTAC function.
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