1.560 RX-ChannelSelect

The RX-ChannelSelect logical device controls the basic parameters of an IRD and an input switch for the IRD which selects frequency band and polarization. RX-ChannelSelect supersedes IRD-Chain device, adding new features like a system wide common satellite channel database. The RX-ChannelSelect device primarily is intended for configurations where several IRDs are connected to an L-band switch matrix which distributes the signals from multiple antennas. It however can be used for simpler applications as well.

The RX-ChannelSelect device translates the user level parameters 'antenna', 'satellite', 'polarization' and 'frequency' into the frequency setting at the IRD and the position of the input selection switch / matrix output. The translation is made following the rules defined in a configuration file. This file describes the switch matrix inputs. The RX-ChannelSelect device does the translation of LO-frequencies, as these may vary for the different antennas.

Beside the function described above, the RX-ChannelSelect device implements a locking mechanism which prevents users from changing parameters at a receive chain which is currently in use. This protection only works on the parameters controlled by the RX-ChannelSelect device, it does not influence the operation of the IRD through it's own screen.

The RX-ChannelSelect device is complemented by the TX-ChannelSelect logical device which may be used to control the equipment of a (DVB) transmit chain in a similar way. Both ChannelSelect devices share the same channel database and the same locking mechanism: While on RX-ChannelSelect device locks an antenna pointing, the TX-ChannelSelect device using the same antenna cannot move this locked antenna.

Device window pages

The following table shows which device window pages are available with this individual device type. Tool-bar functions not mentioned here are described at the general description of device windows .

• --- The main control (channel select) page for the device.
• --- The channel database editor page.
• --- The fault page
  • IRD Lock : The associated IRD is out of lock
  • Config File : The config file is not found, not readable or in a wrong format.
  • IRD Summary : The associated IRD shows a summary fault (includes Lock fault).
• --- The device info page.
• --- The maintenance page. The configuration parameters from this page are described below.

Operation (channel select)

Selecting an already defined satellite channels is a simple 3-step procedure:

1. Select the antenna you want to use at the 'antenna' drop down selection box. This fills the 'satellite' box with a list of satellites (antenna pointing) stored with this antenna. The satellite the antenna actually is pointed to is pre-selected.
2. Now select the satellite you want to receive. The antenna gets commanded to point to the selected satellite and the 'channel' selection gets filled with the channel selection stored for this satellite.
3. Select the channel you want to receive. This tunes IRD to the frequency / symbol rate / fec settings stored for this channel and commands the l-band matrix output port to select the antenna port associated with this frequency abd / polarization.

Instead of selecting the satellite and channel you also may enter the receive parameters at the frequency / pol / symbol rate / fec fields. The RX-ChannelSelect device forwards these settings to the IRD and selects the l-band matrix input to route the selected signal from the antenna to the IRD.

Operation (database edit)

With the second page of the device window of the RX-ChannelSelect device channel definitions are edited, copied or deleted. All RX-ChannelSelect devices in a sat-nms M&C share one common channel database. Changes you make at one device apply to all others as well. Selecting channels at his page or changing any channel parameters do not change the receiver settings.

To edit the channel database, first select the satellite which broadcasts the channel you want to edit. The 'satellite' selection offers all satellites, receivable by any antenna of the station as a whole. The subsequent steps depend on what you want to do. Here a few examples:

• Change certain parameters of a channel:
  1. Select the channel to modify
  2. Edit the settings
  3. Click 'SAVE'Please note that if you change the channel name, this will store a new channel definition with the modified data, the old channel is kept unchanged in the database.
• Save the actual receive settings as a new channel:
  1. Click 'READ' to fill the fields from actual receive settings.
  2. Optionally complete the transmit frequency / polarization.
  3. Enter a new (for this satellite unique) channel name.
  4. Click 'SAVE'
• Delete a channel:
  1. Select the channel to delete
  2. Click 'DELETE'

Configuration parameters

At the maintenance page of the device window there are a couple of configuration parameters which must be set to interconnect the RX-ChannelSelect device with the IRD and the input switch.

Reference channels

For mobile SNG applications the RX-ChannelSelect device is capable to tune the IRD to a special channel as soon as the antenna gets moved to a satellite. This special channel is used to search and identify the satellite. To setup the RX-ChannelSelect device to use this feature, configure the following settings:

At the maintenance page of the RX-ChannelSelect device set the 'refChannel' configuration setting to a non-empty value. For most applications, it makes sense to use the same channel name for all instances of the device. Usually you will name the reference channel "Find-Satellite", "default" or something similar. You also may want to prepend the name with a "Z" to get the reference channel sorted at the very end of the list "Z-default".

Now, for each satellite of interest, define a channel with the name you defined above. The channel should address a DVB signal at the satellite which is very likely to be present all the time.

If you select a satellite with the reference channel setup made as described above, the RX-ChannelSelect device commands the satellite name to the antenna and in parallel it tunes the IRD to the parameters of the reference channel.

If for the given satellite no reference channel is available or if the reference channel name isn't configured at all, the RX-ChannelSelect device will not program the receiver until the operator explicitly selects a channel.

Configuring an M&C with RX-ChannelSelect devices

Unlike other logical devices, which know all links to other parameters / devices from configuration settings, the RX-ChannelSelect device refers to the IRD it controls by it's name. This mainly is because of the IRD device icon which is contained in the RX-ChannelSelect's device window.

The name of the IRD controlled by an RX-ChannelSelect device always must start with an "I" followed by the suffix contained in the RX-ChannelSelect name. The suffix is everything including and following the last hyphen in the name or any trailing digits. The list below shows a few examples for explanation:

When you select a name for the RX-ChannelSelect device, you must name the IRD following this scheme to make the IRD being controlled by the RX-ChannelSelect.

Using the lock/unlock mechanism in a task-oriented screen

The RX-ChannelSelect's lock/unlock mechanism works through the variables 'locked' and 'togglelock'.

To make a parameter in a task-oriented screen 'protected' by the RX-ChannelSelect device (i.e. the parameter only can be changed it the RX-ChannelSelect is 'unlocked'), set the 'locked' flag of the RX-ChannelSelect as the 'enable ID' of the parameter. Example: you want to protect the 'program' parameter of IRD I-3. The chain device is named CHN-3. Set the 'enable ID' field for the 'program' parameter to 'CHN-3.locked' and the 'enable Val' to 'false'. The parameter will be grayed out and treated as read-only as soon as the chain device is locked.

The satellite selection (and in some configurations polarization setting too) may be locked even if the RX-ChannelSelect itself is unlocked. This happens if another RX-ChannelSelect device is locked and set to use the same antenna than this one. In this case we must not select another satellite because this would move the antenna and therefore would break the running reception. For this reason, the satellite position parameter is locked by 'satLocked' variable, the polarization setting by 'polLocked'.

To control the locked state of a RX-ChannelSelect device from a task-oriented screen, introduce a Parameter-Button element which sends the special value '%IP%' to the 'togglelock' variable of the RX-ChannelSelect device. The user interface expands the '%IP%' to string 'username@ip-address' which is used to identify username and workplace from where the RX-ChannelSelect device gets locked.

The configuration file format

The RX-ChannelSelect's configuration file is a plain text file which defines the matrix / switch input assignments. As this is a system wide assignment, you usually will edit one common configuration file for all RX-ChannelSelect devices connected to one input matrix.

In the file all empty lines and lines starting with a '#' character are ignored. All other lines are treated as table rows where the cells are separated by space characters. Each row describes one matrix input as follows:

• column --- contents --- remark
• 1 --- switch position / matrix input --- If the input numbering starts at one or at zero, depends on the matrix / switch device driver.
• 2 --- antenna name --- The antenna name must not contain spaces, commas ot pipe characters ('|').
• 3 --- polarization --- A one letter code, one of the follwing:H for horizontal V for vertical P for polarization offset With the latter selection, the RX-ChannelSelect device commands the Antenna-Pointing device of the antenna to select the polarization plane by turning the feed.
• 4 --- LNB LO frequency for this port --- The LO frequency must be given as a decimal number (MHz) with a decimal point (no commas, no thousand's separators are allowed)
• 5 --- < or > --- If this column contains ' < ', the switch position is used for frequencies below the limit contained in the nect column. ' < ' works the other way round.
• 6 --- frequency limit for this port --- The frequency limit must be given as a decimal number (MHz) with a decimal point (no commas, no thousand's separators are allowed)

Example:

#
#  Example configuration file for a RX-ChannelSelect device
#
#
#  input no.    polarization      freq. limit [MHz]
#  |            |                 |
#  |   antenna  |  LO freq. [MHz] |
#  |   |        |  |              |

   1   ARD      H  9750.0         < 11850.0
   2   ARD      V  9750.0         < 11850.0
   3   ARD      H  10600.0        > 11850.0
   4   ARD      V  10600.0        > 11850.0

   5   NDR      H  9750.0         < 11850.0
   6   NDR      V  9750.0         < 11850.0
   7   NDR      H  10600.0        > 11850.0
   8   NDR      V  10600.0        > 11850.0
   
   9   EBU      H  10000.0        > 0.0
  10   EBU      V  10000.0        > 0.0

  11   TTC      P  10000.0        > 0.0
  12   TTC      P  10000.0        > 0.0

  13   ASTRA    H  9750.0         < 11850.0
  14   ASTRA    V  9750.0         < 11850.0
  15   ASTRA    H  10600.0        > 11850.0
  16   ASTRA    V  10600.0        > 11850.0
  
  17   SNGR     H  9750.0         < 11850.0
  18   SNGR     V  9750.0         < 11850.0
  19   SNGR     H  10600.0        > 11850.0
  20   SNGR     V  10600.0        > 11850.0
  
  21   I605     V  9750.0         > 0.0

  22   W1       V  10000.0        > 0.0
  

The RX-ChannelSelect device parses this file on startup and when it receives a new name for the configuration file. So when you change the configuration file in the running M&C system, the best way is to restart the M&C server process to make all IRD-CHain devices read the configuration file again.

Variables defined by this device driver