RE: using heli (dx7) tx and reciever on my boat project
Nothinbetr2do is correct, unless you are using a surface or multiuse radio system,you are taking the chance of destroying someone's aircraft. It's also illegal per FCC regulations, though the chance of getting caught is relatively small.
Now, getting to the range question, ALL RADIOS HAVE LESS RANGE ON THE SURFACE THAN IN THE AIR. This is due to ground clutter and, in the case of boats, reflection. With the relatively low power we use for R/C's, anything getting between the transmitter and receiver weakens the signal. This was especially true with the pre-1991 radios. In the instructuctions I received with my pre-91 radios, they listed the range in the air at up to .5 miles while the ground range was half of that. With the newer FM, PCM and 2.4 systems, the effect may not be as pronounced, but it is there. The new 2.4 systems have the additional problem of signal reflection off the water's surface. This is something the manufacturers are trying to remedy with every upgrade to the system they release for sale