Here you can define how measurements are performed.
Declination is the angle between the direction to the Arctic magnetic pole of the Earth and the geographic north direction. Since the declination depends on the location and changes over time, it must be adjusted accordingly. The value can be taken from a map of the region you are moving in.
The magnetic declination has to be set only, if Compass is used to determine the north reference (see Configuring the north reference).
Setting the magnetic declination:
1. Tap the Magn. Decl. button.
2. Turn the Rotary knob or enter a value to set declination.
3. Press the Rotary knob or tap the OK button.
Bearings are displayed in the polar chart of the Bearing view. The angles plotted at the polar chart are the direction relative to a given north reference. This north reference can be determined in three ways:
The ADFA has a built-in magnetic compass. When Compass is selected, the bearings in the polar chart are showing the direction related to magnetic north (0° means north, 180° south, ...).
In order to transfer the displayed direction to the map, the local magnetic declination must be determined and entered (see Setting the magnetic declination).
• If the ADFA is mounted on a tripod, you can use this method to align all bearings to north.
• When the ADFA is mounted on a vehicle, the Compass method should NOT be used due to the metallic environment and the magnetic mount adapter.
• Always ensure, that the compass calibration is still valid (e.g. using another compass for comparison).
The ADFA has a built in GNSS module. When moving, the SignalShark calculates the north direction by correlating the positions received via the GNSS data. Since the Compass method can not be used in a metallic environment, this setting should be used, if the ADFA is mounted on a vehicle.
• The reference mark notch of the ADFA must be aligned as accurately as possible to the direction of travel.
• For GNSS north direction accuracy, see also Velocity Squelch.
The base plate of the ADFA has a notch that can be used as reference direction. An arrow on the radome points in the direction of this notch. Alignment tips mounted to the ADFA base plate can be used to align the ADFA in notch direction to a reference point.
If the magnetic compass is not precise enough, you can use this method to align the ADFA to a landmark (e.g. a hill or a big building):
1. Align the ADFA with help of the alignment tips in the direction of the landmark.
2. Determine the position of the ADFA.
3. Draw a line between the ADFA position and the landmark.
4. Calculate the angular difference between this line and the direction to north.
5. Enter this value into the parameter button Ref. Mark. Dir.
The reference mark direction can also be used for presentations:
1. Connect SignalShark to a big screen or beamer.
2. Align the ADFA with its notch in the direction of the screen.
3. If you now move a transmitter around the ADFA, the audience can easily follow the bearing results on the screen.
The reference mark direction setting is needed only, when North Reference is set to Ref. Mark. Dir. (see Configuring_the_north_reference).
Setting the reference mark direction:
1. Tap the Ref. Mark. Dir. button.
2. Turn the Rotary knob or enter a value to set direction.
3. Press the Rotary knob or tap the OK button.
The parameter Azimuth Corr. can be used to add an additional known azimuth deviation.
For example:
• If the ADFA is mounted on a car, but the reference mark is not exactly aligned to the direction of travel, you can use this parameter to enter the number of degrees of deviation.
• You can determine this deviation by using a test transmitter aligned exactly to the middle of the front of the vehicle. The transmitter should be located several ten meters away from the car.
Tap to set the number of counted scans.
The Stop Mode defines the behavior of the measurement engine, after stopping a measurement.
Tap to toggle Hold / Stop.
• After stopping the measurement, the Run key and button light up blue.
• The Scan Count continues in the background.
• After starting the measurement again (Run key and button light up green), Scan Count continues with the number it counted in the background.
• After stopping the measurement, the Run key and button lights up red.
• The Scan Count stops.
• After starting the measurement again (Run key and button light up green), Scan Count starts from 0.
Only signals with a level higher than the DF Squelch parameter will be used as a bearing. This parameter can be used to separate strong signals from low ones and to avoid bearings degraded by the noise floor.
Setting the squelch:
1. Tap the DF Squelch button.
2. Turn the Rotary knob or enter a value to set direction.
3. Press the Rotary knob or tap the OK button.
It is important for a correct bearing result, that the signal level is constant during a complete bearing cycle. Therefor, SignalShark calculates the level difference of the omnidirectional antenna element between two cycles.
With the parameter min Stability you can enter the maximum level difference in dB that is allowed during a bearing cycle.
This parameter can be helpful to:
• Discard bearings with too much level fluctuations.
• Guaranty correct pulse acquisition.
Setting the squelch:
1. Tap the min Stability button.
2. Turn the Rotary knob or enter a value to set direction.
3. Press the Rotary knob or tap the OK button.
A bearing is determined by finding the maximum correlation of the measured covariance vector with the covariance vectors stored in a reference data set.
The DF quality is the magnitude of the maximum correlation in percent.
This parameter can be used to filter out bad bearings.
DF quality value of a good bearing should be greater than 50%. For frequencies smaller than 200 MHz, no DF quality is displayed. Elevation is also not available here. |
Setting the minimum DF quality:
1. Tap the min. DF Quality button.
2. Turn the Rotary knob or enter a value to set direction.
3. Press the Rotary knob or tap the OK button.