Hi Jim,
Firstly, thanks so much for your help.
The copter uses 2.4ghz for video, and 5.8ghz for control. The 900mhz module is an alternate module for control, which has more range and more features in its software and hardware implementation.
The quadcopter legs are plastic only.
However, 3 legs contain various things:
2 contain 5.8ghz control antennas so I definitely don't want to put another antenna there
1 contains a compass module - same story
Optimally, the antenna should go into the leg that does not contain anything, however this means I would need to run the coax a bit. I can only mount the transmitter in the back of the copter (as the camera is in the front), and the free leg is in the front.
Others who have done this modification have used the compass leg. They report that the range of this transmitter is amazing, and basically exceeds the limits of the on board battery. The antenna is used both for transmitting and receiving control signals. You use it to plan missions for search and rescue work, repetitive flights, etc.
They removed the tube without peeling back the sheath, and I now know this means they have removed half of the dipole. If they get such good range when they messed the antenna, then I am not so worried about the slight angular slant of the leg.
(FYI- One discussion is at: **broken link removed**
)
In practice, the null off the end affects you if you fly directly overhead, and generally you are quite low when directly overhead and this does not present any problems.
The issue basically is, that at 900Mhz the antennas are larger. The 900mhz transmitter is 1000mw, and I would also gain that there would be a little better vegetation penetration at this frequency.
My other choice is to mount an antenna at the top center of the quadcopter. The exact top center would not interfere with the propellers. This would mean mounting a sma female through connector at the top, and threading an adapter cable through the unit.
This would give me the additional flexibility of trying different antennas, like a short quarter wave stub when flying close, and for farther flights using a pinwheel, or larger whips like:
https://www.l-com.com/wireless-antenna-900-mhz-5dbi-rubber-duck-antenna-rp-sma-plug-connector
The downside to putting it on top is some wind loading, but my larger concern is that the gps module is located along the inside top of the unit, and I am concerned that it might somehow be affected if there is an RF wire there and antenna on top. Some users have reported that if they put foil strips around the gps module they pick up more satellites. This leaves me to believe they did a poor job of shielding it from below, and I am thinking if this means I should not put anything above it either.
These are my thoughts, your comments and time are most appreciated.
Joe