300' + of wired, you'll probably need to use RS-485.
Which means you need an MCU at the controller end, paired with a MAX485 TTL to RS-485 converter.
Then another MAX485 at the vehicles end.
Serial TTL or RS-232 starts to have trouble at longer distances.
The only other thing i can think would work is a high power xBee, which is still wireless, but would be capable of much further ranges.
A pair of these would work.
http://www.sparkfun.com/products/8742or a pair of these
http://www.sparkfun.com/products/9099You'd still need an MCU to convert the PS2 controller data to TTL.
So Wired PS2 Controller connects to an MCU such as the atom pro/nano.
Option 1: The controller MCU connects to a high power xBee, which transmits to another xbee on the receiving in, thus controlling the bot.
Option 2: the controller MCU connects to a TTL to RS-485 converter, then you have a long freakin wire connected to another RS-485 converter that's attached to your bot.
The Pro's of option 1 are that it's pretty fool proof. And the 60mW xBees should have zero problem reaching the 300' range. The cons, it would set you back about $100
The pros of option 2, it would only cost about $20.
The cons of option 2 far outweigh the pros. The wires at that range would be heavy. So depending on the size of the bot, it would add unnecessary strain on the bot.
A 300+ foot wire would be tough to coil up. And would be easily susceptible to damage.
1 kink, and it would take you
hours to find the kink.
So i'd suggest forgetting about wired, and just go with a high power xBee.
I personally use class1 bluetooth, and i can get over 300feet LOS, but if you want serious range, a high power xBee is the only logical solution.
Wired is for like <20' for movable bots. or 100'-200' for stationary. Longer than that and you want wireless.