17
Status Menu
Gain, Signal to Noise
The first screen displays the FS700's gain and signal-to-noise ratio.
The gain is the gain necessary to bring the selected station to full scale
signal level. The maximum value is 120 dB. Noise Margin indicates the
current LORAN signal quality. A noise margin of 0.0 db is the poorest
quality signal useable by the FS700. The maximum value is +55 dB.
The gain number is not displayed until after station selection, while the
noise margin is not calculated until after the third zero crossing is
located.
Phase
The second screen displays the instantaneous frequency offset of the
FS700's oscillator from the LORAN signal. That is, it is the value of the
last correction that the FS700 made to its oscillator. The time average
of this value is zero. The oscillator has a sensitivity of about 1 x 10
-
11
minimum step size. Also displayed is the instantaneous phase of the
FS700's sampling gate relative to the LORAN pulse (in degrees). The
long-term fractional frequency difference over any time interval may be
calculated from the following formula:
For example: Suppose at the start of a 24 hour period, the phase is 0.1
degree. While at the end of the time interval, the phase is 0.2 degree.
Then the average frequency difference is :
This means that over a 24 hour period the FS700's oscillator is every
bit as good as the source in the LORAN transmitter. The transmitter's
Cesium clock is accurate to about 1-2 x 10
-12
over the same time
period.
Receiver Gain: 75dB
Noise Margin: 33dB
LORAN Frequency Offset: 2.0 E-11
Phase: 0.2°
Stations Found (Ident: Amp in dB)
M57 V38 W45 X70* Y44
