Where do I attach the aerial on the Hitachi 55PMA550 ??

You have bought a monitor NOT a tv. You need to buy/obtain a separate tuner box for tv signals then connect your tuner box to your monitor.

It's most likely the smps. You'll first need to check voltages at CN63, pin #1-(+5v), 3-(+3.3v) and pin 8-(+6v) Also check CNPPS, pin 1-(+30v), 4-(+5v), 8-(+12v), 12-(+10v) absent these values and the power supply is clearly the problem.

I have Hitachi 55PMA550 the problem is that when i switch on the light turns green and nothing happens and then i swich off it turns red

All marine VHF radios must be licensed. A marine radio station must also have a call-sign allocated to the vessel it is installed in. Shore based stations can also be licensed but only where they are involved in marine based activities e.g Yacht Clubs, Marinas, Harbour Masters, Rescue Services etc.
In the UK ships radio licences can be obtained from Ofcom. They are free for non-commercial users.
The user must also have a Marine VHF Radio operators certificate. This requires taking an exam. In the UK contact the Royal Yachting Association for a copy of the syllabus and local examiners.
More information about the licensing rules, courses and exams can be found here. http://www.rya.org.uk/infoadvice/regssafety/Pages/licensingelec.aspx
The ICOM ICM55 is a good radio set and can still be used in an existing (marine) installation but it does not meet the standards for new installations as it does not have DSC (digital selective calling) capabilities - which all new fixed sets must now have. It is therefore very unlikely that you will be able to get a licence to install one.
To get it working you will need a proper marine band VHF aerial which operates in the frequency range 156-MHz. They usually come with cable attached but if a longer cable is needed, or the aerial is not cabled in the first place, use flexible 75 ohm co-axial cable with a copper core and braid/foil screen. Use proper aerial connectors (type F or BC are most commonly used and can be obtained from most good electronic component suppliers more cheaply than from a boat chandlers. Do not use push-fit TV aerial plugs)
Citizens Band radio works on the much lower frequency MHz band and therefore a CB aerial will not work with a marine VHF radio set. Please see this Wikipedia article for more information http://en.wikipedia.org/wiki/Marine_VHF_radio

To fix the problem, try accessing the system setup manually Once there look for NTSC option in the system and select it as the default system setting the black and white output will be changed to colored.

looks like main power supply is not working. Board replacement only.Unless TV shuts off. Then, it might be other things.
Good luck.

The best type of aerial for digital reception is to use a wideband aerial this will give you a better spectrum to receive the signal. To locate the aerial position, if you know in which direction your local transmitter is situated, then point the aerial in that direction. The best way to find out which way to point is to simply look around at any of your neighbours aerials & then aligned yours in the same direction. If you are using a spectrum analyser as your sattelitte finder then you can use this to find other frequencies in the signal range.

The ariel switch is for a power antenna to make it rise when you turn your stereo on. The orange wire is for your dimmer when you turn on your car lights. You do not need to hook either of these up.

Hi What you probably need is a line transformer.
If you have 300 ohm "twin lead " from outside and the receiver has coax , you need a 300 to 75 ohm transformer.
If you have a coax coming in to 2 screw terminals on the receiver , you need a 75 ohm to 300 ohm transformer.
Some place like Radio Shack or a stereo store would have them.

You can buy an RF modulator and a set of composite cables(RCA jacks- red/white/yellow) and attach the aerial coax to the modulator and the compostite from the modulator to tv.
Hope this helps you.