Go to the guys selling computer parts. Buy an rs 232 cable (as shown in Diagram 1). You can take the picture along with you for them to understand. Both ends of the cable should be female (with holes) See attached diagram. The connections will be
pin 2-----------------------------------pin 3
pin 3-----------------------------------pin 2
pin 5-----------------------------------pin 5
Though it may be difficult for you to physically know what connects to what, i will give you my own style.
Take a cutter (or knife, pliers) and cut your cable into 2 at the midpoint (middle), you will find 9 coloured cables including a Unclad one. You will only need the Green, Orange, Red and the Unclad cable. Connects it like this at both ends.
END 1 END 2
Red ------> connects to <----------- Orange
Orange ------> connects to <----------- Red
Green -----> connects to <----------- Green
Unclad wire ------> connects to <----------- Unclad wire
If you connect it well, then you are good to go. (make sure you cover the connected ends with cello tape before you destroy your decoder oooo)
Check the diagram for more details.
However, if your own cable is different, you will need a Multimeter (in the diagram) to test the cable to actually determine pin 2, 3 and 5 then you cross it as is shown in the diagram. How do you test? Alright, Turn the multimeter in such a way as if you are testing for the resistance of the cable e.g. 2k, then connect one end of your Multimeter to pin 2 (second hole from right) (see pin diagram 1 -5, 6 – 9) and then the other end of the meter, use it to touch each ends of the coloured cables to test. If there is a deflection(analog) or value (for digital) , then you know that is the cable for that particular hole (pin 2) . Do the same to determine pin 3 and 5. The Unclad cable is easy to see. You can then connect the cable to your decoder and PC to start the transfer.
[You must be registered and logged in to see this image.]
Home 
