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  • How do I change the polarity of a 9797 antenna?
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There times when additional bandwidth can be obtained for a C-band ship on a satellite beam with the opposite polarity. Often times this is a hemisphere beam that has additional power (and thus more bandwidth or reduced cost) at the price of a smaller footprint. If the ship is only operating in a small area, one of these beams may be perfect, but it requires operating on the opposite polarity than the typical HiSeasNet beams. As such, there are the usual satellite settings changes to make, but also a minor change to the antenna hardware on the ship. Various techs have described these changes in great detail with excellent photos. See the following:

Sometimes the feed horn is not super accessible. Robbie Laird of WHOI describes his process for getting at this item through just the bottom hatch alone (no side door):

Basically, you loosen the lower antenna stops. At that point, get out of the dome and grab the bottom of the dish. bring the dish all the way down and you can then get back inside the dome in front of the dish. I then used a small ladder laid against the dome to get to the feedhorn. You will need to tie the ladder in place somehow. I would suggest replacing two of the bolts on the "equator" with longer ones, and put the nut on top. (so you have a bolt sticking up.) It's also helpful to turn around one of the bolts down low, so you can tie the bottom of the ladder, otherwise it tends to go side to side. (even at the dock) Basically, four bolts sticking out, (away), from the ladder. A small step ladder will fit through the hatch, although some step ladders are smaller than others.

If you use this procedure, its probably a good idea to replace those lower antenna stops to where they were so that the dish is protected from damage by the frame.

Do not attempt this work with the antenna energized. The entire system (antenna motor control and RF signal) must be OFF to safely perform this work!

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