I see this is a very old thread, but I had the same range problem with mine. So, I selected an unused Ardunio pin and drove it with the Tone() command. I think it was at 1kHz. Added a couple of diodes and caps to make a voltage doubler. (for testing I also did a two stage doubler to make it near 14 volts - which was out of speck, but at the cheap cost I thought its ok if I blow it. It was good).
I also added the antenna as well got the whole thing as high off the ground as I could reasonably do. (to avoid grand losses.) All done, I got the range range above 150 ft.
I also considered making a parabolic reflector or Yagi antenna, but I didn't need it.
Just for fun I also swapped out several receivers and they all had quite a bit of difference in sensitivity (all using the 17 cm antenna). I was surprised.
As a couple final steps, I added some filters between the receiver module and the power off the receiver Arduino, and added some long lines connecting the two to get the receiver as far away as I could from the Arduino.
For something is simple, they can be made to work very well.