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Annex Nextfield
Operation and Maintenance
4.2.6
Special Notes to DVOR with Nextfield Monitor
4.2.6.1
Switching On and Setting of DVOR with Nextfield Monitor
The nextfield monitor monitors the radiated DVOR-signal from its position at the edge of the counter
poise. The signal however is not equivalent to the farfield and is not suitable for phasing of the installa
tion. The 9960 Hz modulation depth is determined from two signals with an individual AGC each. It
can be set correctly only in the monitor if it is correctly in the signal in space.
During first alignment it is therefore recommended to phase the installation with the monitor signal
of a mobile or fixed field dipole. Here, the modulation depth of the 9960 Hz is also to be set. After this
alignment the mobile field dipole can be dismantled. The fine adjustment of the 9960 Hz modulation
depth is performed during flight check. If due to the geographical position of the DVOR installation,
e.g. on a mountain, a normal field dipole cannot be installed the phasing and setting of the 9960 Hz
modulation depth is performed during flight check only.
NOTE:
The carrier antenna has very carefully to be adjusted for a good RF matching. A directional
coupler is inserted in the RF line to the carrier antenna, which couples out the sideband
signals, USB and LSB, which are received from the sideband antennas, and supplies it
to the subassembly Monitor (MSP-D). The interference signal reflected by the carrier an
tenna is about 20 to 30 dB greater than the received wanted signal. The worse the mat
ching of the antenna the more unfavorable is the signal to noise ratio and the inaccurate
are the monitor measurement values. Possibly it is indicated only less than 30 % of the
9960 Hz modulation depth due to a bad matching of the antennas, especially of the mid
dle antenna.
The monitor program used for nextfield monitoring processes both signals of the nextfield dipole and
of the conventional field dipole. Therefore the following procedure is recommended:
1. Adjustment of the installation with conventional farfield monitor (fixed or mobile).
2. Adjustment with nextfield monitor
4.2.6.2
Setup of the Installation with Field Dipole and Monitor
The DVOR installation is commissioned either including nextfield monitor or with nextfield monitor as
supplementary part. First the installation is set to operation with the farfield dipole.
- Close all windows in the ADRACS user program.
- Select 'Adjustments' in the function key bar
- Select windows for 'MON-1' and 'Miscellaneous'.
- Set 'Station type' to 'DVOR Farfield signal' and confirm.
The further setup procedure follows according section 4.3.
The farfield dipole is no longer used after a following change over to operation with nextfield dipoles:
a mobile field dipole remains connected until the end of the setup process, while the solidly installed
dipole can be connected permanently.
Ed. 01.04
.
Î
DVOR 432
Alignment Procedure
AN-13
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