SeaTel DAC 2202 Satellite MenuSatellite Menu | SAT: Satellite Longitude | THRS: Threshold | FREQ or MHz: Tracking Frequency | Baud or KHz | Tone ON/OFF- 22KHz | Volt: HORZ, VERT, RHCP, LHCP | FEC: Forward Error Correction | Skew | NID: Target Satellite Network ID | NID FFFE on Galaxy 95W FEC 2/3* | Forced or Pseudo NID (FEC*) | Save Parameters |
The Satellite menu contains tracking information for the target satellite. The first screen displays the selected satellite longitude, the threshold, the tracking frequency and the satellite ID decoded from the satellite.
To change the satellite longitude, press ENTER. Only the SAT longitude will be displayed in the top left hand corner. Press the left arrow to edit mode and the cursor will appear under one of the digits. Use the up and down arrows and left and right arrows to change the digits to the correct satellite longitude and to change to W or E as appropriate. Press ENTER to target the new satellite.
You can use the same procedure to retarget the same satellite if the antenna has tracked off onto something else. When re-targeting the same satellite, there is no need to change the digits, but you do need to use the left arrow to go to edit mode, as if you were going to change the satellite and then ENTER to begin the targeting.
If Auto Threshold is set in the setup menu, the antenna will automatically adjust the threshold based on the off-satellite and on-satellite signal levels it sees, each time it targets the satellite. If Auto Threshold is set to 0000 (manual) then the threshold can be set manually in this screen.
In most situations, the setting is not critical as long as it is well above the noise floor and well below the satellite peak to keep operating in variable conditions. If the threshold is set way too low, the antenna will happily "track" the noise in every direction, whereas if it is set above the on-sat AGC it will continue to search even after it has found the satellite.
To set the threshold manually it needs to be between the on-sat and off-sat AGC levels. Subtract the off-satellite AGC from the on-satellite AGC. Divide this delta by two (or by three) and add this to the off-satellite AGC as the threshold.
On-Satellite AGC 1800 minus Off-Satellite AGC 1620 = 180
divided by two = 90.
New THRS = 1620+90 = 1710
Some manual tweaking may be necessary, especially if there is a strong signal on an adjacent satellite. Bear in mind that the noise floor and situation can change over time, and with location requiring the manual threshold to be revisited. Auto Threshold is therefore clearly the mode of choice, as this will adapt with each retarget, as conditions change over time.
If the FEC is set to AUTO or any other ratio the display will show FREQ.
In either case this is where one enters the tracking L-Band frequency in MHz provided by your VSAT satellite operator or calculated from TV frequency listings on the web.
Sometimes with VSAT they will have you track the same carrier that you are communicating on, but if this is a small signal it is often better to use a large TV carrier on the same satellite. Unless you know the origin of the signal, there is always the risk that the carrier might me removed or changed without your knowledge.
For TV listings it is necessary to deduct the LNB local oscillator frequency from the listed Ku-Band frequencies to obtain an L-Band tracking frequency. For example a Ku-Band Frequency on 101W of 12297 MHz less the LNB local oscillator of 11250 would give you a tracking L-Band frequency of 1047 MHz.
It is important to note that SCPC (narrow band) tracking will only work correctly with an SCPC tuner. Many TV DACs and some older VSAT DACs only have a DVB tuner installed.
The AGC signal on the bottom right is the receive signal strength of the signal.
If the FEC is set to AUTO or any other ratio, this field will display as Baud which is essentially the width of the carrier. The TV Baud rates are available on sites like lyngsat.com or your VSAT provider can recommend a baud rate for the carrier that they suggest to track.
Having the correct baud rate is important if you plan to use satellite NID to positively identify that you are on the right satellite. Otherwise, if you are just tracking an unknown carrier, it can be reduced to a point where you get the maximum difference between on-satellite and off-satellite AGC. If you do not know what the correct baud should be try 08000 or 10000.
The VSAT, SMW quad band LNB can be controlled from the DAC with tone on older VSAT systems. The newer systems do not pass tone from the DAC through the FSK modems, but rather regenerate the tone in the antenna. With this type of system the tone is controlled in the STATUS menu with the band selection. For example B1, for Europe, is with tone OFF, and B2 for USA is with tone ON. Older systems can achieve the same result using the tone from the DAC in this menu.
TV LNBs are also controlled by the tone in this menu and the voltage in the next menu. With 22KHz tone the LNB switches to high band, and with tone off the LNB switches to low band. (13VDC switches to vertical and 18VDC horizontal polarization).
The same is true via a multiswitch for European 4 channel LNBs. This setting on the DAC is critical if the DAC receives the tracking signal via a multiswitch.
Single band VSAT LNBs should be set to the higher voltage setting of HORZ or LHCP to provide 18 VDC to the LNB, although it seems to work OK with the lower, 13V setting too.
The dual band VSAT SeaTel LNB 124917 requires 18V HORZ for high band 11050 MHz and 13V VERT for Low band 10300 MHz LO.
The European quad TV LNB requires 18V HORZ for horizontal transponders and 13V VERT for vertical transponders.
If the DAC has a DVB tuner (wide band TV) then the FEC can be set to AUTO where the tuner will automatically adjust to the correct FEC ratio. You can also enter the specific FEC for the carrier you are tracking if that information is available. This information should be available from your VSAT provider or from the TV listings on websites like www.lyngsat.com.
FEC or Forward Error Correction is a special way that data is coded to prevent and reduce errors due to noise or weak signals. This is used in satellite TV broadcast signals and it is important to have the correct setting if you are tracking a TV signal, for the DVB tuner to lock on to the carrier and decode the NID. When set to AUTO, the tuner will automatically identify the FEC ratio, and this is most commonly used. For example, the FEC for 101W is 6/7 and for 95W it is 2/3. The available FEC settings are 1/2, 2/3, 3/4, 6/7, 7/8 or AUTO.
You will notice that some FEC settings in the DAC have an asterisk. These are for a special function described later. Scroll through the options until you find the required setting without the asterisk.
(For example, a satellite at 28.2E targeting the UK at 0E might offset the satellite skew so that the polarization in the UK area is close to zero).
This Skew adjustment on the DAC 2202 allows one to adjust the polarization for each particular satellite, without changing the antenna POL OFFSET setting in the setup menu, which will effect all satellites that the vessel can target. The Skew adjustment is normally set to zero and the POL OFFSET is adjusted in the setup menu for all satellites. The Skew adjustment only changes for satellites that have this special satellite skew.
The Skew adjustment is for each particular satellite whereas the POL OFFSET is for all satellites.
On vessels using automatic beam switching, (ABS) and openAMIP protocol between the modem and the antenna controller, the Skew setting can also be included in the modem option file so that Skew is updated for each satellite, when automatically changing satellites. This setting is included by the Network Operation Center (NOC) when they create the option file for the modem.
This would only apply to a VSAT antenna with linear polarization where the pol angle alignment with the satellite is critical to avoid interference with other carriers on the opposite pol.
Adjusting the skew only applies with POLANG TYPE set to auto (0072). The skew setting adds or subtracts to the target polang that is calculated by the DAC based on the vessel position and the satellite longitude. Each digit represents one degree on pol angle.
If the antenna does not receive a matching NID from the satellite, it will assume that it is not on the correct satellite and continue to retarget every few seconds to try and lock onto the correct satellite with the required NID.
If you are tracking a known carrier from a satellite with a known and reliable NID, you can enter the NID here. It is important that all your satellite settings match the satellite you are tracking so that it will decode the NID.
The NID on this screen is the target NID setting, whereas the NID displayed on the main satellite menu screen (at the top of this page) is the NID received and decoded from the satellite. Make sure that you are receiving a steady and reliable NID before entering anything in this field. The NID is in hexadecimal digits (ie 0-F). For example, the NID from the satellite at 101W is FFFE and appears to be extremely reliable.
This only applies to DVB TV tuners. On VSAT installations the NID must be set to 0000 to avoid re-targeting, and to allow external network lock to be supplied by the VSAT modem.
In SCPC mode the "decoded" NID on the main satellite screen will show up as a pseudo NID of 1234 or ABCD.
With the FEC set to the appropriate rate with an asterisk *(star), the antenna will generate a pseudo NID, only if the DVB tuner achieves a lock on a carrier with the required frequency, baud rate and FEC parameters. This pseudo NID can then be set in the target NID field. If the antenna tracks off onto the wrong satellite, that does not have the unique frequency, baud, FEC combination, then the pseudo NID will disappear (just like a real NID) and the antenna will retarget.
The pseudo NIDs generated by the antenna are FFFE for DSS signals and FFFD for DVB signals.
To save parameters, briefly press the left and right arrows together until SAVE NEW PARAMETERS is displayed. Press the left arrow again to edit mode, and ENTER.
PARAMETERS SAVED will be displayed. Press NEXT to return to the main menus.