Most small (portable?) planers have a serious snipe problem. All planers have this problem to some extent. Snipe occurs when the planer head drive rollers enter or leave the ends of the board being planed. The planer head shifts slightly and the cutter head digs into the board being planed, producing a slight dip or hollow across the board. Some portable planers have a head lock to reduce this problem, but most still have it and some of the cheaper models have it severely.
If you are planing a long board and can waste the first and last 6" of the board, snipe will not be a problem for you. Just cut it off and use the middle area of the board for your work. If you can't waste this area there are tricks that can reduce it but you probably won't be able to totally eliminate it.
The first trick is to start planing a scrap of the same thickness about 3' long. When this scrap is fully running through the planer head (off to one side) insert your good board. When the scrap comes fully out of the planer head, hold it ready by the planer to run back through the planer just before the end of the good board is reached so the planer always starts and ends on the scrap and not on your good board. Having the scrap going through the planer head will keep the head level and prevent the head from tipping at the time that the leading and trailing ends of the good board are going through, so the good board will not receive the snipe. You can also raise the ends of the in-feed and out-feed tables and this will also reduce the snipe, but you will likely never completely eliminate it.
The only portable planer that I know of that produces no snipe (it actually still does but it's almost non-existent) is the DeWalt DW735. It does this by using 4 posts to hold the head level, plus in-feed and out-feed tables to keep the board being planed as level with the cutter head as possible. I own one of these (my third portable planer) and I still get a snipe line across the boards, but it's so small that it can be removed with a couple of swipes of 150 grit sand paper.
Central North Carolina