18
Stations Found
The third screen displays the identification and amplitude of all stations
found during the search phase of station acquisition. The amplitudes
are displayed in relative dB, and the station that the FS700 is locked to
has a "*" next to it. The station identifications will be displayed if the
FS700 knows them. If the master station is not found, the
identifications will be listed as "?". If there were no stations assigned at
the time of the FS700's manufacture the stations will be listed as "M",
"A","B", etc., since the station labels are unknown. This display is
useful in determining the number and strength of the stations in the
receiver's location.
Status Timing
The fourth screen displays the amount of time that the FS700 has been
locked to its station. This timer can go up to 32767 hours (3.75
years)before it rolls over back to zero. Also displayed is the duration of
the most recent time at which the FS700 was unlocked. If the FS700
has never been unlocked this number will be 0:0:0. However, if the
FS700 ever became unlocked and had to reacquire a station, the length
of time until it became relocked will be displayed. These two times may
be used to determine when the FS700 became unlocked.
Signal Quality
The last screen displays information on the quality of the received
signal and any transient conditions that may have occurred. The letters
a, r, b, n, and o indicate the status of antenna, rf, blink, noise margin,
and oscillator warnings. If the letter is displayed in lower case, the
condition has not occurred. If the letter is in UPPER case, the
condition has been detected in the past. When a warning condition is
detected, the associated status indicator is set. The indicators may be
reset by pressing EXC. Relocking the receiver will also reset the
indicators. The various warnings are described below in the
TRACKING PROBLEMS section.
Track Point Monitoring
It is useful (or confidence building) to monitor the FS700's tracking point
(the third zero crossing). This is easily done using a digital oscilloscope
that is capable of averaging many signal traces (such as the HP
54501A). The averaging is necessary to reduce the noise on the signal.
While the FS700 is locked, the GRI SYNC output on the FS700's rear
panel provides a negative going pulse every GRI 500 ±5
µ
s before the
third zero crossing. The GATE output provides a negative going pulse
that brackets the third zero crossing. To monitor the tracking point,
trigger the scope with the GRI SYNC pulse. After the FS700 has
locked, display the LORAN OUTPUT and GATE output on the scope
using a 10
µ
s/div scale with 500
µ
s of trigger delay. This puts the gate
Time Since Lock:12:34:56
Length Last Unlock:
0:00:00
Signal Status: A r b n o
Press EXC to clear status
