Frequently asked questions
98-141779-G Chapter 8: Service 8-21
8888
8.8.2 The questions
8.8.2.1 Q1: What is OTC and what happens?
OTC stands for One Touch Commission. OTC is similar to a P1dB compression test for VSAT
but on multiple frequencies. The GMU will instruct the antenna to point away from the
Clark belt (geostationary satellites), disable the Power Amplifier (PA) of the BUC and use a
built-in Power Detector to measure the gain of the system from GMU tx-connector up to
BUC PA. The GMU will transmit a Continuous Wave (CW) from 950 MHz - 1950 MHz in
50 MHz increments and store the BUC calibration file on the GMU file system. OTC takes
about 10-15 minutes to perform.
Automatic OTC is only performed once when the GMU boots for the first time because the
GMU from factory does not have any BUC calibration file stored yet. The BUC calibration
file: buc_calibration is located in the GMU Linux file system directory:
/sysopt/buc/
8.8.2.2 Q2: The antenna points towards the wrong Inmarsat GX satellite, what do I
do?
You do nothing and wait until the GMU times out and automatically selects the next
satellite in its list.
The GMU has three Inmarsat GX satellites defined in its satellite list. From factory the GMU
has only a default beam map file loaded and will therefore search for the satellites one by
one. iDirect calls this Round Robin. This may take about 5 -10 minutes per satellite before
the GMU times out and tries the next satellite in its list. After logon to the correct GX
satellite the Inmarsat system will download an Over The Air (OTA) beam map and at next
boot up the GMU should select the correct satellite.
If the ACU is switched OFF or the view towards the GX satellite is blocked the GMU will time
out and start the Round Robin scenario. This can take many minutes before the GMU
selects the right GX satellite again from its satellite list.
8.8.2.3 Q3: There is an ACU WARNING BUC calibration outdated, what do I do?
Make a new manual OTC and wait until the GMU reboots and sends a new pointing request
via OpenAMIP to the ACU. This clears the warning.
The ACU WARNING BUC calibration outdated is always shown after a cable calibration
because it is mandatory to perform a new OTC. Cable calibration is normally only done at
installation of the antenna or if the antenna cable or connectors have been changed or in a
service situation.
To Next Page
Loading...
Need help?
General
