I have been running a simple RF link between 2 arduini uno recently and everything went faily well. I am now trying a new project with an arduino mini pro (5V/16MHz) and the seeeduino RF link (@315MHz), and I see very odd results : when the transmitter is on USB cable, the link runs ok, but when on a 9V battery (as raw voltage input), I get very very limiter range (a few inches).
Because the setup works on USB, I'm assuming that the current limitation on the GPIO that powers the RF transmitter is not the issue here. It therefore has to be the battery itself or the regulator.
Somehow I need to use a GPIO to shut down the radio during power saving phases. My current design is very basic, I should probably add a transistor to enable power on the RF. I was also thinking maybe the RD oscilliator needs to settle down a bit, I may need to add some delays before starting to send data. I can see on the oscilloscope that the data and power PINs seem to behave correctly, although I have noticed a voltage drop on the power pin which is similar in pattern to the data transmitted (but again this is no issue unless using the 9V battery).