In order to send channel changing codes from your Arduino you'll have to read your remote's channel changing codes... on your Arduino! Here's how we'll get that done.
First you'll need to download IRremote.zip below and unzip it into your Arduino's, "Library," folder. I'm using Arduino version 0018 and my directory looks like this;
This is Ken Shirriff's infrared library that's capable of recording and displaying raw pulse codes. Since it gives raw codes instead of only specific company protocols it should work with any remote sending IR pulses.
Next set up your Arduino like the picture. If you're looking at the black lense of your 38kHz IR Receiver:
the leftmost Receiver pin gets jumped to Arduino digital pin 11
the middle Receiver pin gets jumped to Arduino Gnd
the rightmost Receiver pin gets jumped to Arduino 5V
Then plug your Arduino into your computer and open your Arduino software. From the File menu select;
Click on the Upload button and once your sketch is uploaded to your Arduino click on the Serial Monitor button. There's a picture pointing out these buttons if you get lost.
Now point your remote at the 38kHz Receiver and you should see your Serial Monitor come to life when you push a button. We'll want to click the remote buttons 0 through 9 one at a time and save the pulses we get from each so we can clean them up and put them in our Arduino sketch later on.