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SeaTel 4003

SeaTel 4003 | SeaTel 4003 - Aligning the Polang Pot | Aligning the pot single handed (without assistance) |
The 4003 has been the work horse of the last decade and have only recently been superceded by the 4006, 4009 and 4010.

The majority of 1m VSAT antennas currently in service are still the 4006. The 4006 uses a DAC2200 or 2202 antenna controller whereas the 4003 used the DAC03 which was a digital version of the old TAC92.

The 4003 was limited to elevations below 80 degrees, and used a flexible coaxial cabel between the BUC and the feed, which resulted in some loss of transmit power. The design of the 4006 eliminated the elevation problem and came out with a waveguide feed and a waveguide rotary joint between the BUC and the feed.
This is intended as a reference for technicians familiar with the SeaTel 4003 setup. Do not attempt this procedure if you are not qualified to do so. Note, this only applies to the 4003. The 4004, 4006 and later are different.

Note that on earlier models, the motor and mounting remain stationary and only the feed and LNB rotate. On more recent models the motor and everything else rotates.

For the 4003 polang pot to be correctly aligned, with the TX POL set to 0002 and the POL OFFSET set to 0030, the POL potentiometer should be set to 120 which is approximately mid travel of the 3 turn pot, when the LNB is in the vertical position, with the coax connector at the top. This position is actually the horizontal RX pol.

The normal way with an assistant:
With an assistant at the antenna controller using two way radios or cellphones, you can align the polang by setting the POLANG TYPE from 0072 to 0009 (manual), setting the POL OFFSET to 0030, setting the TX POL to 0002 and driving the LNB to the vertical position as shown. Then, loosen the pot and adjust until the assistant says that the POL (in the Antenna menu) reads 120. Then engage the pot keeping it as close as possible to 120.

You need to verify that the POL can be driven in manual mode from about 0042 to about 0218 where it should stop before hitting any obstacles or stressing any cables.

Then set the POLANG TYPE back to 0072, target your correct satellite and call the NOC to do a cross pol alignment.
 CAUTION: Beware getting your fingers caught in the gears. The geared motor is extremely powerful.
Verify the POLANG TYPE is set to 0072 auto
Set POL OFFSET to 0030.
Set TX POL to 0002 (TX Vert / RX Horz)
Set SAT to your own longitude. ( If the vessel is at 80W, set SAT 80W)
Verify POL in antenna menu is automatically set to 120 or close.

Go to the antenna and view the position of the LNB. If it is not exactly vertical, as shown in the picture, loosen the Polang pot and disengage it from the sprocket by moving it away from the feed carefully, without rotating the pot.  When you rotate the pot the feed will move. Be ready to shut down the breaker if necessary.

You can now carefully steer the feed by slowly turning the sprocket on the pot just a few teeth one way or the other. The motor will drive the feed opposite to the movement of the pot. If it goes the wrong way, move it back to the starting point and continue a few teeth in the opposite direction.  

Steer the feed with the pot until the LNB is exactly vertical then move the pot back to center so that the feed stops moving. The LNB is now vertical, and the POL angle will still be about 120 where the feed stops. This is where the antenna calculates it should be for a satellite at your longitude. Carefully engage the sprocket of the pot with the gear. 

As you engage the gears, the feed may move slightly and then stop, due to the spacing of the gears, and that can't be helped. This will be corrected when you set your POL OFFSET during cross-pol alignment with the NOC.

You can now target the correct satellite and the antenna will calculate and rotate the POL to the correct setting for the satellite. You may need to change your TX POL from 0002 back to 0004 if that is required for your satellite.
It is essential that you call the NOC and tell them that you need to do a cross-pol alignment after polang repairs. Failure to do this could degrade your service and cause interference on the satellite if you are not exactly aligned with the satellite.

It is important to verify that the feed can move from a lower limit of about 0042 to an upper limit of about 0218 without hitting obstacles or snagging cables. The POL should stop moving when it reaches these limits and still can be driven back the other way. 

CAUTION: If feed hits a physical stop, or obstruction it can easily strip the gears inside the motor gearbox.

If, for some reason, the feed gets out of control during adjustment and you cannot find the null point,  rotate the pot all the way to the end (beyond software limits) and it should stop, or kill the breaker. You will then need to set the pot back to its 1-1/2 turn mid point before starting again.