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Select AM / 123.1 MHz on the test box and press OK. Then, select either Img (= Image) or
Ord (= Ordinary). In both modes there is a choice to measure the Frequency or check the AF
modulation.
If you wish to measure the frequency, activate the transmitter WITHOUT modulation and press
Frq on the test box. Frequency and signal level are shown on the LCD display and are also
stored in the memory.
If you wish to check the AF modulation, activate the transmitter WITH modulation and press
AF on the test box. The AF signal can be heard in the test box loudspeaker.
When checking the AF modulation, please note that the test box will limit a strong input signal in
order to protect the loudspeaker.
Signal level
This mode can be used to check the signal strength level of the received signals at 156.300
MHz and 156.525 MHz transmissions respectively.
The level figure is used to indicate if the signal strength is sufficient to ensure proper radio
communication between the test box and the GMDSS station during the following tests.
Use this setup:
For an indication of the actual signal strength level, select Signal level on the test box and
press OK. Select frequency. Then, press OK and start transmission from the radio. The level
figure appears in the test box display. A figure of 70 or higher is advisable.
Test sensitivity
In the Test sensitivity mode, the test box outputs a modulated signal on VHF channels 6, 13, 16
and 67 respectively. With an external attenuator (not supplied with the test box) this test can be
used to check the sensitivity of a ship's VHF radio. The modulated signal can be heard and
checked in the radio's speaker as a 1 kHz tone.
Use the setup below. It is very important to use coax cables for the connection of the
equipment.
ATTENUATOR
18
VHF TRANSMITTER
ANT.
VHF RECEIVER
ANT.
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