by RCModelReviews » Mon Feb 28, 2011 9:25 pm
Not such a good idea -- unless you are *very* careful about where you point that antenna.
Hi-gain antennas don't give you something for nothing. The higher the gain, the narrower the radiation pattern so the more sensitive they become to orientation.
I notice this especially with my 5.8GHz video system. Using the 5dBi antenna on the receiver, the signal is *much* worse when the model is above about 45 degrees from the horizon but much better when it's below that angle (when compared to the standard 2dBi antenna. That's because the 5dBi antenna gets its gain by "squashing" the radiation pattern to give more gain horizontally but far less vertically.
With such an antenna on your RC transmitter, you'd have to hold it perfectly vertical to ensure your model got a decent signal at distance and if you pointed that antenna directly at the model (even at relatively close range) you'd likely lose the signal completely.
A better way (providing you're not flying with others on 2.4GHz in the immediate vicinity) would be to use one of the cheap WiFi boosters to up your transmitter's power to (say) 500mW. Of course that may not be legal -- depending on where you're based.
For what it's worth, your stock-standard 2.4GHz RC system ought to give you at least 2 miles (and most likely 3-5 miles) of range once your model is in the air so unless you need more, I wouldn't get too worried.
If in doubt, fit a "return to launch" system and just keep flying until failsafe kicks in and the plane turns around.
RCModelReviews.com, just the facts.