Hello ,
I have Little Experience in Wireless . So i want help from forum users or Mikrotik Support . I buy a Mikrotik RB433AH + R52Hn Card . Now i Wana Use 2ghz band . So Please tell me which Channel Width is best for 2.4ghz(Wifi) ? 20mhz or 40mhz ? I m Waiting ur Best Answer 
40MHz is almost useless in 2.4GHz mode. Best channel width is dependent on what you want to do, what your intended clients are and the local noise floor, other band users, etc.
What are your plans, what are your intended clients, etc?
i wana configure Mikrotik as a AP . i have 30 clients & I m using 15dbi omni antenna with 1 watt external amplifier . Height of Antenna is 80 feet . Now tell me wht i do
It is fine setup but you should have to use 20mhz channel width and 5th channel.
IMO the 1 Watt amp is not going to help you.
Amplifiers also amplify noise.
30dbm amp + 15dbi antenna=45dbm xmit power (32 watts not legal in usa)
I hope you’re not in my area. lol
20Mhz spacing on any clear channel should work for you.
Throw away the amplifter and buy couple of Dbii F50-PRO’s …
http://www.dbii.com/f50-PRO.html
Plug it to the RB433, use SXT or SEXANT for clients and you are ready to do some music 
Some of us should learn to read…
I just want to help him do some resonable network and no monkey-bussiness in 2GHz band But if he want … then lets go with 20MHz channel in very noisy and narrow band … Good luck 
Amplifier? in which world are is that? remove it? which environment? do a scan and find free channel, use 20 unless you are running a private net and not for public connectivity then you can use 40 since most devices operate on 20
He says he wants to use 2 Ghz SXT and Sexant are 5 Ghz
Simply, do not use 2G products at all … Except wifi hotstops and so on …